CA1082463A - One chuck grinding apparatus for end milling cutters and the like - Google Patents
One chuck grinding apparatus for end milling cutters and the likeInfo
- Publication number
- CA1082463A CA1082463A CA315,886A CA315886A CA1082463A CA 1082463 A CA1082463 A CA 1082463A CA 315886 A CA315886 A CA 315886A CA 1082463 A CA1082463 A CA 1082463A
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- Canada
- Prior art keywords
- end mill
- wheel
- workhead
- tooth
- grinding
- Prior art date
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Abstract
ONE CHUCK GRINDING APPARATUS FOR END MILLING
CUTTERS AND THE LIKE
ABSTRACT OF THE DISCLOSURE
Apparatus for manually sharpening the bottom, radially divergent, flute ends or cutting edges of an end milling cutter (hereinafter referred to as an "end mill") which apparatus includes: a stationary, beveled disc-type or plain grinding wheel mounted for rotation about a horizontal axis (or y-axis), so as to present the face of the wheel to an operator, and a tool-holding fixture having a base member mounted on the worktable of a conventional tool grinder. The worktable of the grinder is capable of movement along three axes, namely a longitudinal axis (or x-axis), a horizontal axis (or y-axis) toward and away from the circular face of the disc, and a vertical axis (or z-axis), by manual manipulation of individual table-adjucting wheels. The fixture includes a workhead mounted on a carriage which inturn is translatably mounted for linear to and fro motion, on a base member withbearing means The workhead is mounted on the carriage for pivotable movement about a longitudinal axis (x-axis). An end mill holder comprising a bushing or collet is rotatably disposed in the workhead so that the end mill may be rotated about the end mill's longitudinal (vertical) axis. The end mill is held in a vertical plane, and index plate means are preferably provided for indexing each cutting tooth or edge of an end mill along the y-axis before it is sharpened. Once the end mill is locked into the holder, or "chucked", the end mill may be dished and gashed, and primary and secondary clearances of the flute ends may be provided, all without removingthe end mill, hence the "one chuck" designation.
CUTTERS AND THE LIKE
ABSTRACT OF THE DISCLOSURE
Apparatus for manually sharpening the bottom, radially divergent, flute ends or cutting edges of an end milling cutter (hereinafter referred to as an "end mill") which apparatus includes: a stationary, beveled disc-type or plain grinding wheel mounted for rotation about a horizontal axis (or y-axis), so as to present the face of the wheel to an operator, and a tool-holding fixture having a base member mounted on the worktable of a conventional tool grinder. The worktable of the grinder is capable of movement along three axes, namely a longitudinal axis (or x-axis), a horizontal axis (or y-axis) toward and away from the circular face of the disc, and a vertical axis (or z-axis), by manual manipulation of individual table-adjucting wheels. The fixture includes a workhead mounted on a carriage which inturn is translatably mounted for linear to and fro motion, on a base member withbearing means The workhead is mounted on the carriage for pivotable movement about a longitudinal axis (x-axis). An end mill holder comprising a bushing or collet is rotatably disposed in the workhead so that the end mill may be rotated about the end mill's longitudinal (vertical) axis. The end mill is held in a vertical plane, and index plate means are preferably provided for indexing each cutting tooth or edge of an end mill along the y-axis before it is sharpened. Once the end mill is locked into the holder, or "chucked", the end mill may be dished and gashed, and primary and secondary clearances of the flute ends may be provided, all without removingthe end mill, hence the "one chuck" designation.
Description
108;~463 ONE CHUCK GRINDING APPARATUS FOR END MILLING
CUTTERS AND THE LIKE
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BACKGROUND O~ THE INVENTION
No effort has been spared over the past several decades to develop the 5 numerous modern universal cutter and tool grinding fixtures and machines whichprovide flexibility of operation and are adaptable to many kinds of work. In general, they are designed to hold a milling cutter in a predetermined fixed position and to apply a grinding wheel accurately to sharpen the cutter's cutting edges uniformly and provide desired clearance for the effective utilization of the cutter.
10 It is well known that uniformity of a tool is correlatable to the lifetime of its use, that this uniformity is not attained in manually sharpened tools, and consequently automatically sharpened tools are purchased, particularly for use with numerically controlled machines, 80 the tools can be replaced on a regular basis to minimizedowntime.
A dull cutter, especially an end mill, slows production and gives shoddy results, so it is desirable to sharpen end mills frequently. Usually this is not easily done. To sharpen an end mill easily, requires expensive machine tools beyond themeans of most machine tool shops, especially the small volume ones. Typical of the sophisticated grinders used to sharpen end mills are ones disclosed in U. S.20 Patents 3,719,459; 3,680,262; and 3,813,823, none of which is suitable for the use of a small machine shop operator. Manually operated grinders used to sharpen end mills, which grinders are within the economic and technological means of a smallmachine shop operator, are disclosed in U. S. Patents 2,690,037; 2,958,988;
3,117,399; 3,352,068; and 3,365,843. In no practical m~nual grinding fixture in the 25 prior art is it possible to observe the edges of the teeth while they are being ground.
Conventional manual grinding of end mills is generally effected by inserting the stra~ght shank of a damaged end mill into a chuck held in a motor-driven workhead, and rotating the end mill against a rotating grinding whee} to cut .
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~3~g~;3 off the damaged end, then changing to a small diameter wheel (type No. 1), hollow grinding the end of the end mill, changing to a cup wheel (type No. 11) to grind the cutter clearance on the fluted ends, again changing to a 6" cup wheel (type No. 11) to grind the cutting clearance on the fluted ends, and finally grinding the secondary clearance or relief on the fluted ends. These operations are described in greater detail in available shop manuals such as one published by Covel Manufacturing Company, Benton Harbor, Michigan.
10Those skilled in the art will appreciate the difficulty of grinding an end mill with precision and uniformity by utilizing conventional manual methods; they also appreciate and rue the inordinate expenditure of time entailed in performing a palpably simple task. They will therefore especially appreciate the con-venience and simplicity of being able to utilize a conventional, manually adjustable worktable of a fixed head grinder in conjunction with a fixture which requires only that the end mill be tiltable .
in a vertical plane, to obtain sharp, correctly angled cutting edges, and, that the nearly vertically held end mill be rotatable about its longitudinal axis.
SUMMARY OF THE INVENTION
I have invented an apparatus which is economical to manufacture and use, and which permits an operator in a low-volume machine shop to sharpen the bottom cutting edges of an end mill efficiently and economically. The apparatus of this invention provides a grinding fixture for sharpening the cutting teeth of an end mill held therein and cutting a gash between successive teeth without removing the end mill from the fixture which comprises, a base member, a carriage reciprocably mounted on the base mem~er, means to linearly reciprocate the carriage along a horizontal axis, means to limit the travel of the carriage to a preselected position for each tooth to be sharpened on an end mill rw/d~ ~ 2 -axially held in a generally vertically disposed workhead rotatably mounted on the carriage for rotation about only a longitudinal axis which is at a right angle to the horizontal axis, the work-head including: a barrel member, a sleeve member and cooperating index plate means, the sleeve member being rotatably disposed within the barrel member, the index plate having spaced peripheral serrations the number of which is a multiple of the number of teeth to be sharpened so as to sequentially align each tooth horizontally immediately before it is sharpened, and, detent means operable to hold the index plate in a position to sharpen the each tooth and gash the end mill, so that the teeth are sharpened and the end mill is gashed without removing the end mill from the work-head.
Accordingly, it is a general object of this invention to provide a tool holding fixture for sharpening the radially divergent flute ends or cutting teeth of an end mill with a beveled saucer ordish or disc-shaped grinding wheel (also referred to as a "plain" wheel~, without removing the end mill from the fixture and without moving or changing the wheel, at the same time being able to visually observe the sharpening operation at all times. It will be evident that, where no vertical adjustment of the worktable is to be had, the wheel is to be vertically - 2a -108;~4~3 adjustable.
It is a specific object of this invention to provide a fixture for profile sharpening the plural radially divergent cutting teeth (also referred to as "bottom edges") of an end mill, one tooth at a time, with an essentially nat or slightly5 concave relief, with preselected primary and secondary clearance, by securing the end mill in a generally vertical position and utilizing a fixedly mounted beveled grinding wheel to abrade a rear cutting tooth of an essentially vertically held end mill, so that no "blind" passes are made on the teeth of the tool.
It is also a specific object of this invention to provide a fixture in which 10 an end mill is tilted from the vertical (z-axis), away from the operator for good visibility, and sharpened with a grinding wheel the periphery of which is dressed to a thickness corresponding approximately to the width of the radial gashes separating the cutting edges.
Another general object of this invention is to provide a manual method 15 with the emphasis on speed and simplicity for a semi-skilled operator to sharpen an end mill with uniformity and reproducibility with a rotating, plain grinding wheel, by placing and locking the end mill vertically in the holder of a workhead of a fixture so that the vertical center-lines of the end mill and the wheel are laterally off-set relative to each other, visually aligning a tooth in a predetermined 20 relationship with the periphery of the wheel which is dressed to present a grinding profile having the same width as that of the radial gashes to be made between teeth, tilting the end mill from the vertical and locking the workhead to provide a desired "dish" or hollow grind on a rear tooth which is horizontally aligned but at 8 right angle to the rotating wheel, reciprocating the tooth against the wheel to 25 provide a preselected primary clearance, sequentially indexing the remaining teeth in a horizontally aligned position so as to provide the same primary clearance, elevating the worktable upon which the fixture is mounted to five a predetermined depth of gash, playing the end mill into the wheel until it cuts to the verticalcenter line of the endmill while intermittently gradually elevating the worktable, 3û longitudinally moving the worktable, indexing the end mill $or cutting each gash between teeth, again reciprocatingly $eeding each rear tooth into the wheel to obtain a preselected secondary clearance, and indexing the end mill and grindingeach of the remaining teeth for the desired secondary clearance.
It is a specific object of this invention to provide a grinding fixture $or 35 sharpening end mills without changing a grinding wheel, which ~ixture may be mounted on the manually adjustable worktable of any conventional tool grinder;
which fixture is easily adaptable for use with end mills of arbitrary size; which fixture, mounted for reciprocating the bottom of ~n end mill held therein against a thin-edged or beveled plain grinding wheel rotatable about a fixed horizontal axis, in combination with adjuætments of the worktable, permits an end mill to be ground in a fraction of the time required by conventional manual grinding methods; and,most importantly, which fixture permits sharpening of the cutting edges of end 5 mills with substantially the precision of sophisticated automatic grinding Qppsratus.
These and other objects of the invention, together with some of the advantages thereof, will be apparent to those skilled in the art from the following detailed description of the best mode of carrying out the invention, and the manner of making and using the same, aæ evidenced by the embodiments thereof illustrated 10 in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a conventional tool cutter and grinder with a grinding fixture in accordance with this invention mounted on the worktable of the grinder.
Figure 2 is a front elevational view of the grinding fixture shown in Fig.
1, showing the assembled relationship of the components.
Figure 3 is a top plan view of the grinding fixture shown in Pig. 2.
Figure 4 is a side elevational view in staggered croæs-section along the line 3-3 in Fig. 2 æhowing the mounting of the linearly reciprocable carriage.
Figure 5 is an elevational front detail view of a portion of a four fluted end mill with its vertical center line in laterally spaced-apart relationship relative to the vertical center line of the wheel, to provide primary reliefs.
Figure 6 is an elevational side (right) detail view of the end mill shown in Fig. 5, indicating a tilt of the end mill away from the operator to "dish" the 25 primary surface on each cutting tooth, sequentially.
Figure 7 is an elevational side (right) view of the end mill ready to be gashed, indicating a tilt of the end mill toward the operator, with the right side tooth parallel to the front surface of the wheel.
Figure 8 is a front elevational detail view of the end mill shown in Fig.
30 7 being gashed, the periphery of the wheel cutting to the vertical center line of the end mill, or slightly past it.
Figure 9 is a front elevational detail view, with parts of the wheel and a portion of the right side tooth of the end mill broken away, for grinding the secondary relief, showing the relaffve}y larger relative lateral displacement of35 vertical center lines of end mill and wheel, in comparison with the displacement used to provide primary relief. The rearward tilt of the end mill, generally thesame as that for the primary relief as shown in Fig. 6, is not discernible in this front view.
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, Figure 10 is a front elevational cross-section, with portions broken away, showing a detail of the carriage mounted for linear reciprocation with twin shafts slidably disposed in precision ball bushings fitted in a bearing block.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
S O~ THE INVENTION
As has already been stated hereinabove, the focus of my invention is a combination of a uniquely constructed tool-grinding fixture, referred to generally in Figure 1 by reference numeral 11, and an associate conventional tool grinder (also referred to as a universal cutter and tool grinder) indicated generally by10 reference numeral 12. A suitable tool grinder is typified by Q universal tool and cutter grinder such as Model K 500 made by Kuhlmann America Inc. with a verticalwheel head adjustment, or U. S. Millrite Model FMVN made by U.S.Burke Machine Tool Co., having a fixed grinding head referred to generally by reference numeral 13. Of course a vertically ad~ustable head such as that provided on a Cincinnati15 No. a grinder, or a conventional magnetic surface grinder may also be used, but I
refer herein to a fixed head grinder to draw attention to the fact that the grinder is preferably provided with a grinding wheel 14 mounted for rotation about a fixed horizontal axis (y-axis), so that its surface rotates in a vertical plane, and once the wheel is positioned its axis of rotation is not moved. The grinding wheel 14 is a 2û plain wheel, dish wheel, saucer wheel, or a nat laminar disc-type wheel which is relatlvely thin, that is, having an overall thickness in the range from about 0.12~ in.
to about 0.25 in. These wheels are hereina$ter referred to collectively as "plain wheel", characterized by their beveled rear surfaces, not visible to an operatorstanding directly in front ot the wheel, and a relatively thin, gash-width co-related, ~5 periphery. The wider plain wheel is used for very large end mills in excess of 2 ins.
in diameter. Smaller end mills are preferably sharpened with a thin wheel having a periphery about 0.125 in. in thickness or less.
Whatever the thickness of the wheel 14 it is essential to provide a circumferential grinding periphery 15, as shown in Fig. 7, a detail view on an 30 snlarged scale, which periphery coMesponds in thickness to the width of a gash 27 to be cut in an end mill 20, which is to be shsrpened. Where the thickness of the wheel 14 is greater than the width of the gash, the wheel is beveled at its periphery - to present an acute angle from the front surfRce 16 to the re~r surface 17 (as seen in the detailed enl~ged view shown in Pig. 6). As stated hereina~ove, a saucer 3S wheel, dish wheel, or the lilce, may be used if it meets the foregoing criterion for it~ periphery.
The grinder 12 includes a worktable 21 trsnslatably mounted on a base 22, so that the worktable may, by turning a first hand whed 1~, be moved to and _ 5 _ . ' , : ' . .
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108;~463 - from along a longitudinal (left to right) axis (or x-axis); by turning a second hand wheel 19 the worktable may be cross-fed, that is moved toward and away from the operator along a horizontal axis (or y-axis); and, by turning a-third hand wheel 26, the worktable may be adjusted vertically along a vertical axis (or z-axis), to control 5 the vertical height between the bottom of the grinding wheel 14 and the upper or top surface of the worktable 21. The vertical adjustment may be for the wheel onthe grinding head, rather than on the worktable, as stated hereinbefore.
Removably mounted on worktable 21 is the tool grinding fixture 11 of my invention which is shown in more detail in ~igs. 2, 3, and 4. The fixture 11 10 includes a base member, referred to generally by reference numeral 23, on which is reciprocably disposed a carriage means, indicated generally by reference numeral24. The carriage 24, in turn, carries tiltably disposed thereon, a workhead referred to generally by reference numeral 25.
The base member 23, includes a circular base plate 31, a bearing block 15 30 (seen more clearly in ~ig. 4) above the base plate and a projecting pivot platform 33. The base plate 31 is provided with a vertical bore 32 for passage of a mounting bolt ~not shown) which in cooperation with a nut lodged in a slot of the worktable, secures the base member 23 to the worktable. It is preferred to form the base member 23 as a unit, for example by casting it from a ferrous metal, 20 preferably steel, to allow the base plate 31 to be magnetically secured to the worktable 21, if provision for a magnetic worktable is made. Magnetic worktablesare commonly provided on surface grinders which can thus be used with the grinding fixture of this invention to sharpen a variety of end mil~s.
The projecting pivot platform 33 is provided with a vertical bore 34 for 25 8 pivot bolt 35. The pivot bolt 35 secures a bearing 37 to pivot platform 33. The bearing 37 is press-fitted into a handle 36. The handle 36 serves to reciprocate the carriage 24 linearly as will be explained more fully hereinafter. In operation, pulling on the handle by an operator standing in front of the grinder 12 feeds the c~rriage away from the operator, pushing on the handle brings the carriage toward 30 the operator.
The bearing block 30 is provided with parallel spaced apart bores 40 and 40' (not visible in ~ig. 4) in which bearing means B are fitted. Preferred bearing means are ball bushings such as the Series XA Ball Bushings of Thomson Industries, Inc. and two ball bushings are used in each bore, one at each end. The ball bushings 35 are rehined in the bores with conventional retaining seals and a spacer (not shown) is provided in the bearing block to prevent relative inward movement of the b~llbushings. A detail view of the mounting of the carriage is shown in Fig. 10.
The carriage 24 serves to translate the workhead 25 which it carries, .
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along the horizontal axis (y-axis) toward and away from the grinding wheel 14. The particular structure of the carriage is not critical provided it is accurately translatable linearly, to and fro, along the y-axis. In a preferred embodiment, the carriage 24 comprises a frame 42 having a workhead support 42. The frame 41 and 5 workhead support 42 are preferably formed as a single unit, as by casting.
The frame 41 is provided with end walls 43 and 43' in which end walls a pair of shafts Sl and S2 are tightly fitted horizontally in parallel, laterally spaced apart relationship. It is preferred for minimizing vibrations effects, that the shafts be slightly offset with respect to one another (not apparent in the drawings) so that 10 both are not in the same plane (defined by the x and y axes). The shafts S1 and S2 are inserted through the ball bushings 13 in the bearing block 30, and are slidably precisely supported in the ba~ bushings. Thus the carriage 24 is reciprocable inwardly towards and under the grinding wheel 14 until the end wall 43 contacts the bearing block 30; and, outwardly until the end wall 44 contacts the bearing block.
15 An adjustable stop means 39 is provided in end wall 43 for fine adjustment of the limit of travel, to avoid having to make the adjustment with the cross feed of the worktable.
The workhead support 42 is provided with a stepped longitudinal passage including a longitudinal bore 45 and an annular counterbore 46. As is illustrated, 20 the workhead support 42 is rounded at the top and a reference mark 47 is inscribed thereon, corre~ponding to the vertical position of an end mill held in the workhead which is rotatably supported in the stepped p~ssage.
It will be evident that an obvious modification of the foregoing embodiment of a carriage means is to provide a base member with a vertical 25 ~upport and to employ a carriage translatably disposed on the vertical support, with suitable bearing means.
Referring further to ~ig. 2 it is seen that workhead 25 is mounted on the workhead support 42, so that the workhead is h a generally vertical position. A
draw-h bolt 51 secures the workhead in any desired position whether vertical or 30 angularly disposed to the vertical axis. ~or convenience, the draw-in bolt 51 is provided with a handle 52. -The workhead 25 comprises a generally cylindrical barrel member 55with a stepped cylindrical protrusion extending laterally from the barrel at a right angle with respect thereto. The stepped protrusion includes an outer machined 35 olrcular shoulder 57 the peripheral surface of which is graduated in degrees around its entire circumference, and an axial boss 59 provided with a threaded axial bore 59 in which draw-in bolt 51 is threadedly engaged to secure the barrel 55 in anypreselected attitude which can be read on the graduated scale, in relation to i.
_7 _ .
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~082463 reference mark 47. The barrel 55 is thus rotatably mounted for rotation about the x-axis, which axis of rotation is at a right angle to the longitudinal axis (vertical z-axis) of the barrel. The axial boss S9 snugly fits in the annular counterbore 46.
A sleeve member 61 is rotatably disposed in close-fitting engagement 5 within an axial bore 62 in the barrel 55. The sleeve member 61 is provided at one end with an integral circular index plate 63 which projects radially outwards and rests on barrel 55. The periphery of the index plate is toothed or serrated with a plurality of serrations 64; the number of serrations provided is correlatable to the number of teeth to be sharpened in an end mill, and is a multiple thereof. For 10 example, an index plste with 24 serrations may be used to sharpen end mills with 2, 3, 4, 6, 8 and 12 teeth. An end mill with 5 teeth will require an index plate with a number of serrations which is a multiple of 5.
The index plate 63 cooperates with a spring-biased finger 65 in arresting the index plate in sny desired position by lodging between adjacent teeth. The lS finger 65 is supported on a finger support 66 which is conveniently mounted on barrel 55.
The sleeve member 61 is provided with an axial bore 67 which slidably snugly accommodates a strsight pull-in collet or shaft, and tapered collets and shafts, in a conventional manner. Where, for example, a tapered collet 71 is to be 20 uJed to mount the end mill 20 to be sharpened, the small end of the collet isthreaded to engage threaded draw-in collar 72. When draw-in collar 72 is tightlyscrewed upon the threaded end of the collet 71, it securely holds the end mill therein, snd the end mill may be rotated about an axis in the vertical plane using the index plate 63, without permitting any other movement.
As h~s been stated hereinbefore, it is critical that the carriage 24, and therefore the end mill to be sharpened, be linearly reciprocable at least over the radial length of a tooth to be sharpened. This reciprocable motion is effected manually by moving handle 36 back and forth, pivoting the handle about pivot bolt 35 so that cam follower 73 in cam 74 on the frame 41 causes the carriage to 30 reciprocate as desired, while the grinding wheel contacts the tooth to be sharpened.
A better understanding of the relationship of the elements of my grinding fixture and its unique capability to emit the manual sharpening of the cutting teeth of an end mill, without removing the end mill from the fixture, and utilizing a stationary, beveled plain grinding wheel, will be had from the following 3s detailed instructions for sharpening a standard tour-fluted end mill (right hand cutting teeth), with the aid of the accompanying illustrations. It is to be borne in mind that if there is no vertical adjustment of the worktable, then the grindingwheel must be vertically ad~ustable.
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It will be apparent that the apparatus of this invention permits only an angular primary and secondary relief grind for the bottom cutting edges of an end mill, and cannot provide an arcuate relief grind as is provided, for example, inU.S.Patent No.3,816,955. In other words, each primary face 48 and each angularly5 related secondary face 49 of each tooth is planar rather than curved, since reciprocation of the carriage is linear and not arcuate. It will al~so be apparent that the grinding fixture of this invention will not sharpen the flutes 50 of an end mill.
In the enlarged illustrations, ~ig. 5 illustrates an end mill 20 locked in the workhead to have the primary surfaces 48 cut on the teeth. To sharpen tooth 10 29, teeth 28 and 28' are longitudinally aligned and the end mill is fflted through the plane of the paper (away from the operator) as seen in ~ig.6. The end mill is then gashed, generally with a slight rake about 2 (tilt toward the operator) as shown in Fig.7, and stopped so it is gashed to the center as shown in Fig.8. &condary surfaces 49 are then cut, and are angularly related to the primary surfaces 48 as 15 shown in Fig.9. It will be evident that the sequence of the operations is not critical, but best results are obtained as described below.
SHARPENING AND OPERATION
Mount a "plain" grinding wheel, about 0.25 in. thick, on the arbor of a conventional universal cutter and tool grinder, and dress the periphery of the wheel 20 so it is beveled to about 30 from the vertical, the angle being towards tl e rear of the wheel so that the bevel is not visible from directly in front of the wheel. The periphery of the wheel used is necessarily dressed to the thickness of the gash desired in the end mill to be sharpened. Alternatively a saucer wheel with a thin periphery may be used, though it will be recognized that it too will require that its 25 periphery be dressed as it wears, particularly for relatively small diameter end mills less than about 1 in. in diameter.
Mount the 4-nuted end mill 20, to be sharpened, in the jaws of the collet 71 held vertically in the workhead 25, and tighten the draw-in collar 72 so that the end mill is ffghtly held in the collet with oppositely di~posed cutting teeth 30 aligned along the y-axis, i.e. normal to the plane of the wheel 14. This may be done visually and checked by positioning the worktable so that the longitudinal teeth 28 and 28' lie su~stantially paraUel to the face Or the wheel, without actually contacting the wheel. In this position, the longitudinal axis (vertical) of the end mill b longitudinally (along the x-axis) displaced relative to the verUcal center ~ine 3~ of the wheel 14, and to the left thereof, as i~lustrated in ~ig.5, a distance d, according to known computations, to establish the degrees of primary relief angle or primary clearance desired. Some iJlustrative values, for setting the relativedisplacement are set forth in Table I hereinbelow for some commonly used _g _ -.
~082463 diameters of grinding wheels. For right hand end mills, the end mill is displaced left of the vertical center line of the wheel; as will be evident for a left hand end mill, all the grinding operations are carried out on the right of the vertical center line of the wheel.
The relative displacement 'd' may be approximated visually, but for precision, should be set by reading it on the graduated scale commonly provided on the hand wheel 18 which effects longitudinal (x-axis) movement of the worktable 21.
The end mill is now brought forward along the horizontal axis, away 10 from the wheel, sufficiently to permit the end mi~l to be tilted towards the wheel and away from the operator to provide the desired "dish" for the teeth. Though on occasion, no dish (that is, zero angle) is specified, typically an end mill is provided with from about 2 to about 3. The desired manufacturer's suggested angle (say
CUTTERS AND THE LIKE
.
BACKGROUND O~ THE INVENTION
No effort has been spared over the past several decades to develop the 5 numerous modern universal cutter and tool grinding fixtures and machines whichprovide flexibility of operation and are adaptable to many kinds of work. In general, they are designed to hold a milling cutter in a predetermined fixed position and to apply a grinding wheel accurately to sharpen the cutter's cutting edges uniformly and provide desired clearance for the effective utilization of the cutter.
10 It is well known that uniformity of a tool is correlatable to the lifetime of its use, that this uniformity is not attained in manually sharpened tools, and consequently automatically sharpened tools are purchased, particularly for use with numerically controlled machines, 80 the tools can be replaced on a regular basis to minimizedowntime.
A dull cutter, especially an end mill, slows production and gives shoddy results, so it is desirable to sharpen end mills frequently. Usually this is not easily done. To sharpen an end mill easily, requires expensive machine tools beyond themeans of most machine tool shops, especially the small volume ones. Typical of the sophisticated grinders used to sharpen end mills are ones disclosed in U. S.20 Patents 3,719,459; 3,680,262; and 3,813,823, none of which is suitable for the use of a small machine shop operator. Manually operated grinders used to sharpen end mills, which grinders are within the economic and technological means of a smallmachine shop operator, are disclosed in U. S. Patents 2,690,037; 2,958,988;
3,117,399; 3,352,068; and 3,365,843. In no practical m~nual grinding fixture in the 25 prior art is it possible to observe the edges of the teeth while they are being ground.
Conventional manual grinding of end mills is generally effected by inserting the stra~ght shank of a damaged end mill into a chuck held in a motor-driven workhead, and rotating the end mill against a rotating grinding whee} to cut .
.
:- . . . ..
~3~g~;3 off the damaged end, then changing to a small diameter wheel (type No. 1), hollow grinding the end of the end mill, changing to a cup wheel (type No. 11) to grind the cutter clearance on the fluted ends, again changing to a 6" cup wheel (type No. 11) to grind the cutting clearance on the fluted ends, and finally grinding the secondary clearance or relief on the fluted ends. These operations are described in greater detail in available shop manuals such as one published by Covel Manufacturing Company, Benton Harbor, Michigan.
10Those skilled in the art will appreciate the difficulty of grinding an end mill with precision and uniformity by utilizing conventional manual methods; they also appreciate and rue the inordinate expenditure of time entailed in performing a palpably simple task. They will therefore especially appreciate the con-venience and simplicity of being able to utilize a conventional, manually adjustable worktable of a fixed head grinder in conjunction with a fixture which requires only that the end mill be tiltable .
in a vertical plane, to obtain sharp, correctly angled cutting edges, and, that the nearly vertically held end mill be rotatable about its longitudinal axis.
SUMMARY OF THE INVENTION
I have invented an apparatus which is economical to manufacture and use, and which permits an operator in a low-volume machine shop to sharpen the bottom cutting edges of an end mill efficiently and economically. The apparatus of this invention provides a grinding fixture for sharpening the cutting teeth of an end mill held therein and cutting a gash between successive teeth without removing the end mill from the fixture which comprises, a base member, a carriage reciprocably mounted on the base mem~er, means to linearly reciprocate the carriage along a horizontal axis, means to limit the travel of the carriage to a preselected position for each tooth to be sharpened on an end mill rw/d~ ~ 2 -axially held in a generally vertically disposed workhead rotatably mounted on the carriage for rotation about only a longitudinal axis which is at a right angle to the horizontal axis, the work-head including: a barrel member, a sleeve member and cooperating index plate means, the sleeve member being rotatably disposed within the barrel member, the index plate having spaced peripheral serrations the number of which is a multiple of the number of teeth to be sharpened so as to sequentially align each tooth horizontally immediately before it is sharpened, and, detent means operable to hold the index plate in a position to sharpen the each tooth and gash the end mill, so that the teeth are sharpened and the end mill is gashed without removing the end mill from the work-head.
Accordingly, it is a general object of this invention to provide a tool holding fixture for sharpening the radially divergent flute ends or cutting teeth of an end mill with a beveled saucer ordish or disc-shaped grinding wheel (also referred to as a "plain" wheel~, without removing the end mill from the fixture and without moving or changing the wheel, at the same time being able to visually observe the sharpening operation at all times. It will be evident that, where no vertical adjustment of the worktable is to be had, the wheel is to be vertically - 2a -108;~4~3 adjustable.
It is a specific object of this invention to provide a fixture for profile sharpening the plural radially divergent cutting teeth (also referred to as "bottom edges") of an end mill, one tooth at a time, with an essentially nat or slightly5 concave relief, with preselected primary and secondary clearance, by securing the end mill in a generally vertical position and utilizing a fixedly mounted beveled grinding wheel to abrade a rear cutting tooth of an essentially vertically held end mill, so that no "blind" passes are made on the teeth of the tool.
It is also a specific object of this invention to provide a fixture in which 10 an end mill is tilted from the vertical (z-axis), away from the operator for good visibility, and sharpened with a grinding wheel the periphery of which is dressed to a thickness corresponding approximately to the width of the radial gashes separating the cutting edges.
Another general object of this invention is to provide a manual method 15 with the emphasis on speed and simplicity for a semi-skilled operator to sharpen an end mill with uniformity and reproducibility with a rotating, plain grinding wheel, by placing and locking the end mill vertically in the holder of a workhead of a fixture so that the vertical center-lines of the end mill and the wheel are laterally off-set relative to each other, visually aligning a tooth in a predetermined 20 relationship with the periphery of the wheel which is dressed to present a grinding profile having the same width as that of the radial gashes to be made between teeth, tilting the end mill from the vertical and locking the workhead to provide a desired "dish" or hollow grind on a rear tooth which is horizontally aligned but at 8 right angle to the rotating wheel, reciprocating the tooth against the wheel to 25 provide a preselected primary clearance, sequentially indexing the remaining teeth in a horizontally aligned position so as to provide the same primary clearance, elevating the worktable upon which the fixture is mounted to five a predetermined depth of gash, playing the end mill into the wheel until it cuts to the verticalcenter line of the endmill while intermittently gradually elevating the worktable, 3û longitudinally moving the worktable, indexing the end mill $or cutting each gash between teeth, again reciprocatingly $eeding each rear tooth into the wheel to obtain a preselected secondary clearance, and indexing the end mill and grindingeach of the remaining teeth for the desired secondary clearance.
It is a specific object of this invention to provide a grinding fixture $or 35 sharpening end mills without changing a grinding wheel, which ~ixture may be mounted on the manually adjustable worktable of any conventional tool grinder;
which fixture is easily adaptable for use with end mills of arbitrary size; which fixture, mounted for reciprocating the bottom of ~n end mill held therein against a thin-edged or beveled plain grinding wheel rotatable about a fixed horizontal axis, in combination with adjuætments of the worktable, permits an end mill to be ground in a fraction of the time required by conventional manual grinding methods; and,most importantly, which fixture permits sharpening of the cutting edges of end 5 mills with substantially the precision of sophisticated automatic grinding Qppsratus.
These and other objects of the invention, together with some of the advantages thereof, will be apparent to those skilled in the art from the following detailed description of the best mode of carrying out the invention, and the manner of making and using the same, aæ evidenced by the embodiments thereof illustrated 10 in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a conventional tool cutter and grinder with a grinding fixture in accordance with this invention mounted on the worktable of the grinder.
Figure 2 is a front elevational view of the grinding fixture shown in Fig.
1, showing the assembled relationship of the components.
Figure 3 is a top plan view of the grinding fixture shown in Pig. 2.
Figure 4 is a side elevational view in staggered croæs-section along the line 3-3 in Fig. 2 æhowing the mounting of the linearly reciprocable carriage.
Figure 5 is an elevational front detail view of a portion of a four fluted end mill with its vertical center line in laterally spaced-apart relationship relative to the vertical center line of the wheel, to provide primary reliefs.
Figure 6 is an elevational side (right) detail view of the end mill shown in Fig. 5, indicating a tilt of the end mill away from the operator to "dish" the 25 primary surface on each cutting tooth, sequentially.
Figure 7 is an elevational side (right) view of the end mill ready to be gashed, indicating a tilt of the end mill toward the operator, with the right side tooth parallel to the front surface of the wheel.
Figure 8 is a front elevational detail view of the end mill shown in Fig.
30 7 being gashed, the periphery of the wheel cutting to the vertical center line of the end mill, or slightly past it.
Figure 9 is a front elevational detail view, with parts of the wheel and a portion of the right side tooth of the end mill broken away, for grinding the secondary relief, showing the relaffve}y larger relative lateral displacement of35 vertical center lines of end mill and wheel, in comparison with the displacement used to provide primary relief. The rearward tilt of the end mill, generally thesame as that for the primary relief as shown in Fig. 6, is not discernible in this front view.
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, Figure 10 is a front elevational cross-section, with portions broken away, showing a detail of the carriage mounted for linear reciprocation with twin shafts slidably disposed in precision ball bushings fitted in a bearing block.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
S O~ THE INVENTION
As has already been stated hereinabove, the focus of my invention is a combination of a uniquely constructed tool-grinding fixture, referred to generally in Figure 1 by reference numeral 11, and an associate conventional tool grinder (also referred to as a universal cutter and tool grinder) indicated generally by10 reference numeral 12. A suitable tool grinder is typified by Q universal tool and cutter grinder such as Model K 500 made by Kuhlmann America Inc. with a verticalwheel head adjustment, or U. S. Millrite Model FMVN made by U.S.Burke Machine Tool Co., having a fixed grinding head referred to generally by reference numeral 13. Of course a vertically ad~ustable head such as that provided on a Cincinnati15 No. a grinder, or a conventional magnetic surface grinder may also be used, but I
refer herein to a fixed head grinder to draw attention to the fact that the grinder is preferably provided with a grinding wheel 14 mounted for rotation about a fixed horizontal axis (y-axis), so that its surface rotates in a vertical plane, and once the wheel is positioned its axis of rotation is not moved. The grinding wheel 14 is a 2û plain wheel, dish wheel, saucer wheel, or a nat laminar disc-type wheel which is relatlvely thin, that is, having an overall thickness in the range from about 0.12~ in.
to about 0.25 in. These wheels are hereina$ter referred to collectively as "plain wheel", characterized by their beveled rear surfaces, not visible to an operatorstanding directly in front ot the wheel, and a relatively thin, gash-width co-related, ~5 periphery. The wider plain wheel is used for very large end mills in excess of 2 ins.
in diameter. Smaller end mills are preferably sharpened with a thin wheel having a periphery about 0.125 in. in thickness or less.
Whatever the thickness of the wheel 14 it is essential to provide a circumferential grinding periphery 15, as shown in Fig. 7, a detail view on an 30 snlarged scale, which periphery coMesponds in thickness to the width of a gash 27 to be cut in an end mill 20, which is to be shsrpened. Where the thickness of the wheel 14 is greater than the width of the gash, the wheel is beveled at its periphery - to present an acute angle from the front surfRce 16 to the re~r surface 17 (as seen in the detailed enl~ged view shown in Pig. 6). As stated hereina~ove, a saucer 3S wheel, dish wheel, or the lilce, may be used if it meets the foregoing criterion for it~ periphery.
The grinder 12 includes a worktable 21 trsnslatably mounted on a base 22, so that the worktable may, by turning a first hand whed 1~, be moved to and _ 5 _ . ' , : ' . .
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108;~463 - from along a longitudinal (left to right) axis (or x-axis); by turning a second hand wheel 19 the worktable may be cross-fed, that is moved toward and away from the operator along a horizontal axis (or y-axis); and, by turning a-third hand wheel 26, the worktable may be adjusted vertically along a vertical axis (or z-axis), to control 5 the vertical height between the bottom of the grinding wheel 14 and the upper or top surface of the worktable 21. The vertical adjustment may be for the wheel onthe grinding head, rather than on the worktable, as stated hereinbefore.
Removably mounted on worktable 21 is the tool grinding fixture 11 of my invention which is shown in more detail in ~igs. 2, 3, and 4. The fixture 11 10 includes a base member, referred to generally by reference numeral 23, on which is reciprocably disposed a carriage means, indicated generally by reference numeral24. The carriage 24, in turn, carries tiltably disposed thereon, a workhead referred to generally by reference numeral 25.
The base member 23, includes a circular base plate 31, a bearing block 15 30 (seen more clearly in ~ig. 4) above the base plate and a projecting pivot platform 33. The base plate 31 is provided with a vertical bore 32 for passage of a mounting bolt ~not shown) which in cooperation with a nut lodged in a slot of the worktable, secures the base member 23 to the worktable. It is preferred to form the base member 23 as a unit, for example by casting it from a ferrous metal, 20 preferably steel, to allow the base plate 31 to be magnetically secured to the worktable 21, if provision for a magnetic worktable is made. Magnetic worktablesare commonly provided on surface grinders which can thus be used with the grinding fixture of this invention to sharpen a variety of end mil~s.
The projecting pivot platform 33 is provided with a vertical bore 34 for 25 8 pivot bolt 35. The pivot bolt 35 secures a bearing 37 to pivot platform 33. The bearing 37 is press-fitted into a handle 36. The handle 36 serves to reciprocate the carriage 24 linearly as will be explained more fully hereinafter. In operation, pulling on the handle by an operator standing in front of the grinder 12 feeds the c~rriage away from the operator, pushing on the handle brings the carriage toward 30 the operator.
The bearing block 30 is provided with parallel spaced apart bores 40 and 40' (not visible in ~ig. 4) in which bearing means B are fitted. Preferred bearing means are ball bushings such as the Series XA Ball Bushings of Thomson Industries, Inc. and two ball bushings are used in each bore, one at each end. The ball bushings 35 are rehined in the bores with conventional retaining seals and a spacer (not shown) is provided in the bearing block to prevent relative inward movement of the b~llbushings. A detail view of the mounting of the carriage is shown in Fig. 10.
The carriage 24 serves to translate the workhead 25 which it carries, .
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along the horizontal axis (y-axis) toward and away from the grinding wheel 14. The particular structure of the carriage is not critical provided it is accurately translatable linearly, to and fro, along the y-axis. In a preferred embodiment, the carriage 24 comprises a frame 42 having a workhead support 42. The frame 41 and 5 workhead support 42 are preferably formed as a single unit, as by casting.
The frame 41 is provided with end walls 43 and 43' in which end walls a pair of shafts Sl and S2 are tightly fitted horizontally in parallel, laterally spaced apart relationship. It is preferred for minimizing vibrations effects, that the shafts be slightly offset with respect to one another (not apparent in the drawings) so that 10 both are not in the same plane (defined by the x and y axes). The shafts S1 and S2 are inserted through the ball bushings 13 in the bearing block 30, and are slidably precisely supported in the ba~ bushings. Thus the carriage 24 is reciprocable inwardly towards and under the grinding wheel 14 until the end wall 43 contacts the bearing block 30; and, outwardly until the end wall 44 contacts the bearing block.
15 An adjustable stop means 39 is provided in end wall 43 for fine adjustment of the limit of travel, to avoid having to make the adjustment with the cross feed of the worktable.
The workhead support 42 is provided with a stepped longitudinal passage including a longitudinal bore 45 and an annular counterbore 46. As is illustrated, 20 the workhead support 42 is rounded at the top and a reference mark 47 is inscribed thereon, corre~ponding to the vertical position of an end mill held in the workhead which is rotatably supported in the stepped p~ssage.
It will be evident that an obvious modification of the foregoing embodiment of a carriage means is to provide a base member with a vertical 25 ~upport and to employ a carriage translatably disposed on the vertical support, with suitable bearing means.
Referring further to ~ig. 2 it is seen that workhead 25 is mounted on the workhead support 42, so that the workhead is h a generally vertical position. A
draw-h bolt 51 secures the workhead in any desired position whether vertical or 30 angularly disposed to the vertical axis. ~or convenience, the draw-in bolt 51 is provided with a handle 52. -The workhead 25 comprises a generally cylindrical barrel member 55with a stepped cylindrical protrusion extending laterally from the barrel at a right angle with respect thereto. The stepped protrusion includes an outer machined 35 olrcular shoulder 57 the peripheral surface of which is graduated in degrees around its entire circumference, and an axial boss 59 provided with a threaded axial bore 59 in which draw-in bolt 51 is threadedly engaged to secure the barrel 55 in anypreselected attitude which can be read on the graduated scale, in relation to i.
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~082463 reference mark 47. The barrel 55 is thus rotatably mounted for rotation about the x-axis, which axis of rotation is at a right angle to the longitudinal axis (vertical z-axis) of the barrel. The axial boss S9 snugly fits in the annular counterbore 46.
A sleeve member 61 is rotatably disposed in close-fitting engagement 5 within an axial bore 62 in the barrel 55. The sleeve member 61 is provided at one end with an integral circular index plate 63 which projects radially outwards and rests on barrel 55. The periphery of the index plate is toothed or serrated with a plurality of serrations 64; the number of serrations provided is correlatable to the number of teeth to be sharpened in an end mill, and is a multiple thereof. For 10 example, an index plste with 24 serrations may be used to sharpen end mills with 2, 3, 4, 6, 8 and 12 teeth. An end mill with 5 teeth will require an index plate with a number of serrations which is a multiple of 5.
The index plate 63 cooperates with a spring-biased finger 65 in arresting the index plate in sny desired position by lodging between adjacent teeth. The lS finger 65 is supported on a finger support 66 which is conveniently mounted on barrel 55.
The sleeve member 61 is provided with an axial bore 67 which slidably snugly accommodates a strsight pull-in collet or shaft, and tapered collets and shafts, in a conventional manner. Where, for example, a tapered collet 71 is to be 20 uJed to mount the end mill 20 to be sharpened, the small end of the collet isthreaded to engage threaded draw-in collar 72. When draw-in collar 72 is tightlyscrewed upon the threaded end of the collet 71, it securely holds the end mill therein, snd the end mill may be rotated about an axis in the vertical plane using the index plate 63, without permitting any other movement.
As h~s been stated hereinbefore, it is critical that the carriage 24, and therefore the end mill to be sharpened, be linearly reciprocable at least over the radial length of a tooth to be sharpened. This reciprocable motion is effected manually by moving handle 36 back and forth, pivoting the handle about pivot bolt 35 so that cam follower 73 in cam 74 on the frame 41 causes the carriage to 30 reciprocate as desired, while the grinding wheel contacts the tooth to be sharpened.
A better understanding of the relationship of the elements of my grinding fixture and its unique capability to emit the manual sharpening of the cutting teeth of an end mill, without removing the end mill from the fixture, and utilizing a stationary, beveled plain grinding wheel, will be had from the following 3s detailed instructions for sharpening a standard tour-fluted end mill (right hand cutting teeth), with the aid of the accompanying illustrations. It is to be borne in mind that if there is no vertical adjustment of the worktable, then the grindingwheel must be vertically ad~ustable.
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It will be apparent that the apparatus of this invention permits only an angular primary and secondary relief grind for the bottom cutting edges of an end mill, and cannot provide an arcuate relief grind as is provided, for example, inU.S.Patent No.3,816,955. In other words, each primary face 48 and each angularly5 related secondary face 49 of each tooth is planar rather than curved, since reciprocation of the carriage is linear and not arcuate. It will al~so be apparent that the grinding fixture of this invention will not sharpen the flutes 50 of an end mill.
In the enlarged illustrations, ~ig. 5 illustrates an end mill 20 locked in the workhead to have the primary surfaces 48 cut on the teeth. To sharpen tooth 10 29, teeth 28 and 28' are longitudinally aligned and the end mill is fflted through the plane of the paper (away from the operator) as seen in ~ig.6. The end mill is then gashed, generally with a slight rake about 2 (tilt toward the operator) as shown in Fig.7, and stopped so it is gashed to the center as shown in Fig.8. &condary surfaces 49 are then cut, and are angularly related to the primary surfaces 48 as 15 shown in Fig.9. It will be evident that the sequence of the operations is not critical, but best results are obtained as described below.
SHARPENING AND OPERATION
Mount a "plain" grinding wheel, about 0.25 in. thick, on the arbor of a conventional universal cutter and tool grinder, and dress the periphery of the wheel 20 so it is beveled to about 30 from the vertical, the angle being towards tl e rear of the wheel so that the bevel is not visible from directly in front of the wheel. The periphery of the wheel used is necessarily dressed to the thickness of the gash desired in the end mill to be sharpened. Alternatively a saucer wheel with a thin periphery may be used, though it will be recognized that it too will require that its 25 periphery be dressed as it wears, particularly for relatively small diameter end mills less than about 1 in. in diameter.
Mount the 4-nuted end mill 20, to be sharpened, in the jaws of the collet 71 held vertically in the workhead 25, and tighten the draw-in collar 72 so that the end mill is ffghtly held in the collet with oppositely di~posed cutting teeth 30 aligned along the y-axis, i.e. normal to the plane of the wheel 14. This may be done visually and checked by positioning the worktable so that the longitudinal teeth 28 and 28' lie su~stantially paraUel to the face Or the wheel, without actually contacting the wheel. In this position, the longitudinal axis (vertical) of the end mill b longitudinally (along the x-axis) displaced relative to the verUcal center ~ine 3~ of the wheel 14, and to the left thereof, as i~lustrated in ~ig.5, a distance d, according to known computations, to establish the degrees of primary relief angle or primary clearance desired. Some iJlustrative values, for setting the relativedisplacement are set forth in Table I hereinbelow for some commonly used _g _ -.
~082463 diameters of grinding wheels. For right hand end mills, the end mill is displaced left of the vertical center line of the wheel; as will be evident for a left hand end mill, all the grinding operations are carried out on the right of the vertical center line of the wheel.
The relative displacement 'd' may be approximated visually, but for precision, should be set by reading it on the graduated scale commonly provided on the hand wheel 18 which effects longitudinal (x-axis) movement of the worktable 21.
The end mill is now brought forward along the horizontal axis, away 10 from the wheel, sufficiently to permit the end mi~l to be tilted towards the wheel and away from the operator to provide the desired "dish" for the teeth. Though on occasion, no dish (that is, zero angle) is specified, typically an end mill is provided with from about 2 to about 3. The desired manufacturer's suggested angle (say
2) is set by aligning and locking the 2 scale graduation on the circular shoulder 57 15 with the reference mark 47 on the workhead support 42.
The end mill is now cross-fed toward the wheel so that the periphery of rotating wheel 14 lies essentially along the transverse axis of the end mill and the cutting edge of the right hand tooth 28 lies parallel to the face of the wheel, while ~ust avoiding contact therewith. The adjustable stop means 39 on the carriage 24 is 20 now set so that the end mill may be fed to the same location by a pulling movement of the handle 36. The end mill is now brought forward towards the operator so that the rear (first) tooth 29 clears the wheel and the worktable is gradually raised until the farthest portion of the rear tooth just contacts the rotating wheeL The end mill is now played into the wheel, pulling on the handle 36, and the rear tooth is 25 ground to the center of the end mill, the end mill being stopped at the preselected location by the adjustable stop means 39. Grinding of the tooth can be observed all the while because the tooth is being sharpened directly in front of, and in full view of the operator. The end mill is then retracted (brought torward towards the operator) so it clears the wheel, by pushing on the handle 3B. If sufficient stock has 30 not been abraded, the end mill is raised a fraction of an inch, by the handwheel 26 for vertical adjustment of the worktable, and the rear tooth is again played (cro6s fed) into the wheel pulling on the handle. The rear tooth is thus sharpened with- the desired primary clearance.
The end mill i8 now retracted to clear the wheel by pushing on the 35 handle 36, the index plate 63 is rotated, the finger 65 clicking o~ 6 of the 24 serrations on the index plate to set the next (second) tooth 28' at the right a~gle to the plane of the wheel. The adiustable stop means having been set for the first tooth, it is not to be reset. llle second tooth is now played on to the wheel, and i . ' .
since- the vertical and horizontal relationship between the second tooth of the end mill and the wheel is the ssme as that of the first tooth, it is sharpened in exactly the same manner. Again the end mill is retracted, indexed to the third tooth 29'and sharpened; and the fourth tooth 28 is similarly sharpened.
Having sequentially sharpened each tooth for primary clearance, the end mill is now ready to be gashed. The end mill is retracted to clear the wheeland the workhead is unlocked so that the end mill can be tilted forward to rake the gash 27 &ccording to manufacturer's standards. Typically 2 is desirable, so thegraduated scale on the circular shoulder 58 of the workhead is aligned for 2 10 against the reference mark 47, and locked. Thus the end mill is tilted as shown in the detail side elevational view in Fig. 7, in the opposite direction from vertical, compared with its tilt for grinding the dished primary clearance. Now to position the end mill properly, it is cross-fed with hand wheel 19 towards the wheel, and to the left side thereof, so that the front surface of the periphery of the wheel is 15 adjacent the right hand tooth which lies parallel to the front surface of the wheel.
The adjustable stop means is set so that the end mill can be advanced no furtherinto the wheel. The end mill is now moved longitudinally to the left of the wheel's vertical center line, and the worktable is raised about an eighth of an inch (one or two turns of the hand wheel 26 for vertical adiustment). Now feed the end mill 20 horizontally into the wheel; moving the worktable to the right by using the handwheel 18 for longitudinal adjustment, so that the wheel cuts a gash to the vertical center line Or the end mill without leaving a small teat at the center. Now set the longitudinal stop on the worktable for this location to limit its longitudinal travel so that the wheel does not cut much farther than the center of the end mill, 25 whereby all gashes will be cut to the same central position. A detailed front view, on an enlarged scale, of the end mill being gashed is illustrated schematically in ~ig. 8. The right hand tooth, the cutting edge of which lies adjacent and parallel to the face of the wheel, but not touching it, is shown broken away, for clarity.
Having cut the gash, the end mill is moved to the left, longitudinally away from the 30 wheel by the handwheel for the worlctable, and the end mi~l is indexed with the index plate, for the next gash, and sequentially, each succeeding gash; and each is gashed in the same manner as the first gash.
After gashing the mill, it may be desirable to repeat the operations for cutting the prim~ry clearance just to put a finish cut on the teeth after gashing, 35 but this ~epetition is not generally necessary. }laving now gashed the end mill, the final operation is to grind the secondary clearances.
The end mill is moved away from the wheel, the workhead loosened and the original tilt of 2 for the primary clearance is reset on the workhead. Move the end mill to the left of the wheel, as illustrated in Fig. 9, showing a detailed enlarged view, with the right side tooth broken away to show the horizontally aligned rear tooth in elevational profile. The tilt of the end mill, to provide the correct dish for the secondary clearance, which tilt is the same for the primary5 relief (as shown in Fig. 6) is not visible in Fig. 9. Now gradually play the end mill towards the wheel while reciprocating the carriage so that the essentially linear segment of the periphery of the wheel corresponding to the secondary clearance, as illustrated by the dashed lines, is moved to and fro over the entire horzontal portion of the cutting tooth. The longitudinal limit of travel d' of the worktable 10 towards the vertical center line of the wheel, is set when the desired secondary clearance is ground on the first tooth. As shown in Fig. 9 it will be apparent that the distance d' is measured with the end mill in contact with the wheel, in a position which gives the desired secondary clearance. The end mill is shown laterally displaced in Fig. 9, for the sake of clarity. The operation is repeated on 15 each of the remaining teeth, simply by moving the end mill away from the wheel, indexing it to the desired tooth and playing the tooth on the wheel, so that all the secondaries are evenly ground.
The bottom cutting edges of the end mill are now fully sharpened without having removed ~he end mill from the collet. Though the apparatus of the20 invention has been particularly described with respect to the sharpening of the bottom cutting edges of an end mill, it will be evident that any cutting tool inwhich angul~rly related primary and secondary surfaces are to be provided on theteeth, for example a shell mill, may be sharpened on this apparatus.
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The end mill is now cross-fed toward the wheel so that the periphery of rotating wheel 14 lies essentially along the transverse axis of the end mill and the cutting edge of the right hand tooth 28 lies parallel to the face of the wheel, while ~ust avoiding contact therewith. The adjustable stop means 39 on the carriage 24 is 20 now set so that the end mill may be fed to the same location by a pulling movement of the handle 36. The end mill is now brought forward towards the operator so that the rear (first) tooth 29 clears the wheel and the worktable is gradually raised until the farthest portion of the rear tooth just contacts the rotating wheeL The end mill is now played into the wheel, pulling on the handle 36, and the rear tooth is 25 ground to the center of the end mill, the end mill being stopped at the preselected location by the adjustable stop means 39. Grinding of the tooth can be observed all the while because the tooth is being sharpened directly in front of, and in full view of the operator. The end mill is then retracted (brought torward towards the operator) so it clears the wheel, by pushing on the handle 3B. If sufficient stock has 30 not been abraded, the end mill is raised a fraction of an inch, by the handwheel 26 for vertical adjustment of the worktable, and the rear tooth is again played (cro6s fed) into the wheel pulling on the handle. The rear tooth is thus sharpened with- the desired primary clearance.
The end mill i8 now retracted to clear the wheel by pushing on the 35 handle 36, the index plate 63 is rotated, the finger 65 clicking o~ 6 of the 24 serrations on the index plate to set the next (second) tooth 28' at the right a~gle to the plane of the wheel. The adiustable stop means having been set for the first tooth, it is not to be reset. llle second tooth is now played on to the wheel, and i . ' .
since- the vertical and horizontal relationship between the second tooth of the end mill and the wheel is the ssme as that of the first tooth, it is sharpened in exactly the same manner. Again the end mill is retracted, indexed to the third tooth 29'and sharpened; and the fourth tooth 28 is similarly sharpened.
Having sequentially sharpened each tooth for primary clearance, the end mill is now ready to be gashed. The end mill is retracted to clear the wheeland the workhead is unlocked so that the end mill can be tilted forward to rake the gash 27 &ccording to manufacturer's standards. Typically 2 is desirable, so thegraduated scale on the circular shoulder 58 of the workhead is aligned for 2 10 against the reference mark 47, and locked. Thus the end mill is tilted as shown in the detail side elevational view in Fig. 7, in the opposite direction from vertical, compared with its tilt for grinding the dished primary clearance. Now to position the end mill properly, it is cross-fed with hand wheel 19 towards the wheel, and to the left side thereof, so that the front surface of the periphery of the wheel is 15 adjacent the right hand tooth which lies parallel to the front surface of the wheel.
The adjustable stop means is set so that the end mill can be advanced no furtherinto the wheel. The end mill is now moved longitudinally to the left of the wheel's vertical center line, and the worktable is raised about an eighth of an inch (one or two turns of the hand wheel 26 for vertical adiustment). Now feed the end mill 20 horizontally into the wheel; moving the worktable to the right by using the handwheel 18 for longitudinal adjustment, so that the wheel cuts a gash to the vertical center line Or the end mill without leaving a small teat at the center. Now set the longitudinal stop on the worktable for this location to limit its longitudinal travel so that the wheel does not cut much farther than the center of the end mill, 25 whereby all gashes will be cut to the same central position. A detailed front view, on an enlarged scale, of the end mill being gashed is illustrated schematically in ~ig. 8. The right hand tooth, the cutting edge of which lies adjacent and parallel to the face of the wheel, but not touching it, is shown broken away, for clarity.
Having cut the gash, the end mill is moved to the left, longitudinally away from the 30 wheel by the handwheel for the worlctable, and the end mi~l is indexed with the index plate, for the next gash, and sequentially, each succeeding gash; and each is gashed in the same manner as the first gash.
After gashing the mill, it may be desirable to repeat the operations for cutting the prim~ry clearance just to put a finish cut on the teeth after gashing, 35 but this ~epetition is not generally necessary. }laving now gashed the end mill, the final operation is to grind the secondary clearances.
The end mill is moved away from the wheel, the workhead loosened and the original tilt of 2 for the primary clearance is reset on the workhead. Move the end mill to the left of the wheel, as illustrated in Fig. 9, showing a detailed enlarged view, with the right side tooth broken away to show the horizontally aligned rear tooth in elevational profile. The tilt of the end mill, to provide the correct dish for the secondary clearance, which tilt is the same for the primary5 relief (as shown in Fig. 6) is not visible in Fig. 9. Now gradually play the end mill towards the wheel while reciprocating the carriage so that the essentially linear segment of the periphery of the wheel corresponding to the secondary clearance, as illustrated by the dashed lines, is moved to and fro over the entire horzontal portion of the cutting tooth. The longitudinal limit of travel d' of the worktable 10 towards the vertical center line of the wheel, is set when the desired secondary clearance is ground on the first tooth. As shown in Fig. 9 it will be apparent that the distance d' is measured with the end mill in contact with the wheel, in a position which gives the desired secondary clearance. The end mill is shown laterally displaced in Fig. 9, for the sake of clarity. The operation is repeated on 15 each of the remaining teeth, simply by moving the end mill away from the wheel, indexing it to the desired tooth and playing the tooth on the wheel, so that all the secondaries are evenly ground.
The bottom cutting edges of the end mill are now fully sharpened without having removed ~he end mill from the collet. Though the apparatus of the20 invention has been particularly described with respect to the sharpening of the bottom cutting edges of an end mill, it will be evident that any cutting tool inwhich angul~rly related primary and secondary surfaces are to be provided on theteeth, for example a shell mill, may be sharpened on this apparatus.
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Claims (6)
1. Apparatus for sharpening the cutting teeth of an end mill and cutting a gash between successive teeth comprising a grinding fixture in which said end mill is removably mounted, and, a grinder having a longitudinally and horizontally adjustable worktable on which said grinding fixture is demountably disposed, and, a plain grinding wheel mounted for rotation about a horizontal axis above said worktable and vertically adjustable relative thereto, said wheel having a periphery the thickness of which is no greater than the width of said gash, said grinding fixture comprising: (a) a base member; (b) a carriage reciprocably mounted on said base member; (c) means to reciprocate said carriage linearly along the horizontal axis toward and away from said wheel; and (d) a generally vertically disposed workhead rotatably mounted on said carriage for rotation about a longitudinal axis only, said workhead in which said end mill is axially held including (i) a barrel member, (ii) a sleeve member and cooperating index plate means, said sleeve member being rotatably disposed within said barrel member, said index plate having spaced peripheral serrations the number of which is a multiple of the number of said teeth to be sharpened, and (iii) detent means operable to hold said index plate in a position to sharpen said each tooth and gash said end mill so that said teeth are sharpened and said end mill is gashed without removing said end mill from said workhead or changing said wheel.
2. The apparatus of Claim 1 wherein said plain grinding wheel is chosen from a laminar disc-shaped wheel a saucer wheel or dished wheel; said means to reciprocate said carriage is a manual means carried by said base member; said base member includes a bearing block and bearing means disposed therein; and, said carriage includes shaft means reciprocably disposed within said bearing means.
3. A grinding fixture for sharpening the cutting teeth of an end mill held therein and cutting a gash between successive teeth without removing said end mill from said fixture which comprises, (a) a base member, (b) a carriage reciprocably mounted on said base member, (c) means to linearly reciprocate said carriage along a horizontal axis, (d) means to limit the travel of said carriage to a preselected position for each tooth to be sharpened on an end mill axially held in (e) a generally vertically disposed workhead rotatably mounted on said carriage for rotation about only a longitudinal axis which is at a right angle to said horizontal axis, said workhead including:
(i) a barrel member, (ii) a sleeve member and cooperating index plate means, said sleeve member being rotatably disposed within said barrel member, said index plate having spaced peripheral serrations the number of which is a multiple of the number of teeth to be sharpened so as to sequentially align each tooth horizontally immediately before it is sharpened, and, (iii) detent means operable to hold said index plate in a position to sharpen said each tooth and gash said end mill, so that said teeth are sharpened and said end mill is gashed without removing said end mill from said workhead.
(i) a barrel member, (ii) a sleeve member and cooperating index plate means, said sleeve member being rotatably disposed within said barrel member, said index plate having spaced peripheral serrations the number of which is a multiple of the number of teeth to be sharpened so as to sequentially align each tooth horizontally immediately before it is sharpened, and, (iii) detent means operable to hold said index plate in a position to sharpen said each tooth and gash said end mill, so that said teeth are sharpened and said end mill is gashed without removing said end mill from said workhead.
4. A manual method for an operator to sharpen an end mill with uniformity and reproducibility with a rotating, plain grinding wheel comrising, placing the end mill vertically in a workhead of a grinding fixture so that the vertical center lines of the end mill and the wheel are laterally off-set relative to each other; visually aligning a tooth in a predetermined relationship with the periphery of the wheel which is dressed to present a grinding profile having the same width as that of the radial gashes to be made between teeth; locking said end mill in position; tilting said end mill from the vertical and locking said workhead to provide a desired dish or hollow grind on a rear tooth which is horizontally aligned and in contact with said rotating wheel, and at a right angle thereto; reciprocating said tooth against said wheel to provide a preselected primary clearance;
sequentiallly indexing the remaining teeth into a horizontally aligned position so as to be ground to the same primary clearance; elevating said worktable to give a predetermined depth of gash; playing said end mill into said wheel until it cuts to the vertical center line of said end mill; indexing said end mill for cutting each gash successively between teeth; tilting said end mill from the vertical and locking said workhead to provide a desired hollow grind; grinding each tooth to provide a preselected secondary clearance by reciprocatingly playing each rear tooth into said grinding wheel while intermittently gradually elevating said worktable;
longitudinally moving said worktable; indexing said end mill and grinding each remaining tooth sequentially by reciprocatingly feeding each rear tooth into said wheel to obtain a preselected secondary clearance.
sequentiallly indexing the remaining teeth into a horizontally aligned position so as to be ground to the same primary clearance; elevating said worktable to give a predetermined depth of gash; playing said end mill into said wheel until it cuts to the vertical center line of said end mill; indexing said end mill for cutting each gash successively between teeth; tilting said end mill from the vertical and locking said workhead to provide a desired hollow grind; grinding each tooth to provide a preselected secondary clearance by reciprocatingly playing each rear tooth into said grinding wheel while intermittently gradually elevating said worktable;
longitudinally moving said worktable; indexing said end mill and grinding each remaining tooth sequentially by reciprocatingly feeding each rear tooth into said wheel to obtain a preselected secondary clearance.
5. The method of Claim 4 comprising, after grinding the primary clerance, and before elevating said worktable to cut the gash, the step of tilting said end mill to provide a desired rake for the gash.
6. The method of Claim 4 comprising choosing a pre-selected off-set of said vertical center lines to provide a desired primary clearance; after playing said end mill into said wheel until it cuts to the vertical center line of said end mill to provide the desired gash, the step of setting a first stop for the longitudinal travel of said worktable; and, after the step of tilting said end mill from the vertical and locking said workhead to provide a desired hollow grind for a secondary face, the step of setting a second stop for the longitudinal travel of said worktable; whereby, all primary faces are identically ground, as are all gashes and secondary faces.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA315,886A CA1082463A (en) | 1978-11-07 | 1978-11-07 | One chuck grinding apparatus for end milling cutters and the like |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA315,886A CA1082463A (en) | 1978-11-07 | 1978-11-07 | One chuck grinding apparatus for end milling cutters and the like |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1082463A true CA1082463A (en) | 1980-07-29 |
Family
ID=4112907
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA315,886A Expired CA1082463A (en) | 1978-11-07 | 1978-11-07 | One chuck grinding apparatus for end milling cutters and the like |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1082463A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106965056A (en) * | 2017-04-28 | 2017-07-21 | 华南理工大学 | A kind of desktop level automatic metallic phase grinding machine |
| CN112975677A (en) * | 2019-12-13 | 2021-06-18 | 嘉兴职业技术学院 | Portable tool grinding machine |
-
1978
- 1978-11-07 CA CA315,886A patent/CA1082463A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106965056A (en) * | 2017-04-28 | 2017-07-21 | 华南理工大学 | A kind of desktop level automatic metallic phase grinding machine |
| CN112975677A (en) * | 2019-12-13 | 2021-06-18 | 嘉兴职业技术学院 | Portable tool grinding machine |
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