US2607173A - Grinding method - Google Patents

Description

19, 1952 c. GARRISON V 2,607,173

GRINDING METHOD Filed July 26, 1947 3 Sheets-Sheet l INVENTOR.

Ch'ffurd L. E'arrzsan C. L.- GARRISON GRINDING METHOD s Sheets-Sheet 2 Filed July 26, 1947 IN V EN TOR. Eh'ffurd L. Garrz'sun BY My a Aug. 19, 1952 c L GARRlSON 2,607,173

GRINDING METHOD Filed July 26, 1947 3 Sheets-Sheet 3 j I X: 97

INVENTOR. BIZ fwd L. Farrz'smz ATTY Patented Aug. 19, 1952 GRINDING METHOD Clifford L. Garrison, Adrian, Mich., assignor to Oliverlnstrument Company, Adrian, Mich., a

corporation of Michigan Application July 26, 1947, Serial No. 763,781

1 Claim.

1 This invention relates to a method of forming, grinding or sharpening tools and more especially to a method of configurating or sharpening form tool bits manufactured of relatively hard materials.

In the manufacture of form tool bits of the character used in machine work for cutting metals and alloys, it has been a recent practice and development to form such tool bits from metal alloys which are extremely hard. By way reason of the fact that the conventional type of abrasive or grinding wheel does not satisfactorily grind or sharpen tools fabricated of this material. When a tool bit formed of comparatively hard metal alloy is brought into contact with the conventional grinding wheel, the tendency is to result in a "burning of the'tool in which the cutting edge does not become sharp but becomes chipped or broken presenting an uneven cutting edge, and the grinding wheel surface becomes glazed by reason of its contact with the hard material.

An object of the present invention is the provision of a method of grinding or sharpening a cutting tool of relatively hard material whereby the grinding operation may be performed in a short space of time and a smooth cutting edge formed upon the tool or cutting instrumentality.

Another object of the invention is the provision of a method of grinding or sharpening a cutting or form tool by impact of a grinding or abrasive medium with the tool.-

Another object of the invention resides in a method of grinding utilizing a grinding wheel especially configurated in a manner providing zones adapted for intermittent engagement with the tool by impact in a manner which substantially eliminates glazing of the wheel and whereby the life of the grinding wheel is greatly prolonged.

Still another object of the invention resides in a method of grinding utilizing a grinding apparatus in which a grinding medium having a mutilated grinding area is arranged for cooperation with a tool supporting means whereby the extent of movement of a tool carried by the'tool supporting means into engagement with the grinding wheel is predetermined or restricted whereby a grinding or sharpening operation upon a tool may be quickly and efficiently completed.

A further object of the invention resides in a method of grinding utilizing an apparatus for sharpening or grinding 'tools of comparatively hard material wherein a complete tool grinding or forming operation may embrace a series of consecutive grinding or tool forming cycles, each of the cycles being limited to removing a comparatively small amount of metal from the tool to be formed or sharpened, each metal removing operation being carried out by impact of spaced grinding areas or zones provided upon the wheel or grinding medium.

Further objects and advantages are within the scope of this invention such as relate to the arrangemnt, operation and function of the related elements of the structure, and to economics of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which: E

Figure 1 is a side elevational View showing a portion of a grinding apparatus utilized in the grinding method of my invention, certain parts being shown in section for purposes of illustration;

Figure 2 is a front elevational view of the portion of the grinding apparatus illustrated in Figure 1; V

Figure 3 is a fragmentary sectional view taken substantially on the line 3-3 of Figure 2;

Figure 4 is an elevational view of a grinding or abrasive element utilized in my invention;

Figure 5 is a sectional view through the grinding element taken substantially on the line 5-5 of Figure 4;

Figure 6 is an elevational view of a modified form of grinding apparatus utilized in my invention;.

Figure 7 is a front elevational view of a form of an abrasive means or unit utilized in my invention;

Figure 8 is a side View of the abrasive unit illustrated in Figure 6; certain parts of the construction being shown in section, and

Figure 9 is an isometric view illustrating one of the segments of abrasive material forming an element of the abrasive unit.

While I have illustrated forms of my invention involving the use of a rotary abrasive unit or means for forming, grinding or sharpening form tools I or cutting instrumentalities, it is to be understood that I contemplate the utilization of the method of forming, grinding orabrading wherever the same may be found to be useful and to employ the apparatus for removing material by impact of an abrading medium with various forms of objects fabricated of hardened material.

Referring tothe drawings in detail, the grind- 3 ing apparatus illustrated in Figures 1, 2 and 3 is inclusive of a base if! upon which is supported an upwardly projecting frame I i. Surrounding the lower portion of frame H is an outwardly extending uniplanar portion 22 boundedby an upwardly extending flange i i, the construction pro viding a receptacle or basin arranged to receive fluid that may be directed against the grinding or abrasive wheel surface for cooling the grinding wheel and object being ground. The base it incloses a suitable fluid pump (not shown) through which fluid in a reservoir contained in the base if! is directed under pressure through a pipe 5 and a flexible conduit to a manifold I! from which fluid, guided by a channelshaped portion 24, is ejected upon the surface of the abrasive wheel H3.

The grinding or abrasive medium in the form of a wheel 18 is mounted upon a shaft 19 which is journaled in suitable bearings (not shown) carried in the frame member. The shaft i9 is provided with a pulley 28 driven by a belt 2! connected to a suitable motor (not shown), the pulley 20 and belt 2i being enclosed in a suitable guard 24. The grinding wheel 68 is substantially enclosed within a housing 22 which is supported upon the frame H by means of a ported in bearings carried by the frame. housing is arranged for adjustment about the axis of shaft 23. To accomplish this adjustment, the frame of the machine is provided with a boss 25 which is bored to accommodate a shaft 26, the latter being provided with an operating or hand wheel 21 at one end, the other end portion being threaded into a nut or bushing 29. The bushing 29 is pivotally supported upon a projection 3! formed integrally with the frame Ii, Thus by rotating the hand wheel 21, the shaft 23 being threaded into bushing 29, the grinding wheel housing 22 may be moved about the axis of shaft 23. The purposes of this adjustment will be hereinafter explained.

The forward portion of the grinding wheel housing 22 is formed with vertically extending ways or tracks 32 of dove-tailed cross section upon which is slidably supported a member 34; The housing 22 is formed with a boss portion 36 which is bored to accommodate a bushing 31. The bushing 3! is fixed in the boss 33 and is interiorly threaded to receive the threaded portion 38 of a shaft 41. Secured to the upper extremity of member 34 is a bracket 39 having a boss portion 48 bored to receive the unthreaded portion of shaft 4! as shown in Figure l. Mounted upon the upper end of the shaft M is a hand wheel 43 for rotating the shaft. Rotation of shaftxdi by means of hand wheel 43 provides a means-for raising 0r lowering the member 34 for a purpose to be hereinafter explained.

In configurating form tools, a templat is utilized with a suitable tool holder for reproducing the tool form on the tool bit. The apparatus illustrated is inclusive of a templateforming or grinding wheel 48 mounted upon a shaft 49 actuated by an electrically-operated motor 53. The motor 50 is mounted upon a platen 5| which is longitudinally adjustable through the medium of a threaded shaft 52, the latter provided with a hand wheel 53 for rotating the shaft. The shaft 52 extends through a threaded bushing 54 carried by the frame of the machine so that rotation of the hand wheel 53 moves the platen 5!, motor 50 and template forming wheel :13. A tool holder supporting means in the form of a semispherically shaped member 51 is mounted upon shaft 23 sup- The a ledge 58 formed on the frame of a machine and is adapted to accommodate a combined tool holder and template carrying means 69. Also mounted upon the machine frame H is a gage or abutment block 6| carried in a mounting bracket E2, the latter being secured to the machine frame by suitable screws.

The holder 66 may be utilized to configurate or profile a template 63 to the shape of a master form tool by utilizing the template grinding wheel 48 in the following manner: The tool holder Gil is provided with means in the form of a block (96 provided with a suitable groove or recess to receive a form tool bit. A pivotally supported camBS is arranged for engagement with the lower surface of the form tool carrying block 64 for wedgedly locking the form tool in the block G4, the cam 85 being moved to locking position under the influence of a threaded member 66. With the form tool so mounted in the tool holder 50, the latter is disposed with a semi-spherical recess 61 formed in the lower extremity thereof fitted over the ball-shaped support 51, the template 63 being in a position to engage the template grinding wheel 38. The operator moves the tool and template holder 69 in a direction to bring the template blank 63 into engagement with the grinding wheel d8 until all portions of the master tool bit'are brought into engagement with the abutment 51. When this occurs, the grinding or profilingof the template 63 ceases because the abutment 8i cooperates with the form tool bit as a limiting means for determining the extent of grinding or abrasion of the template blank 53.

The machine is also provided with a gaging means for coordinating a form tool blank or bit to be ground or resharpened to the configuration of the finished template. In this connection the machine frame II is provided with a second spherically-shaped support it adapted to accommodate the template and tool holder 60. Disposed above the support 78 is a gage plate or block H arranged so as to be engaged by form tool blank carried by the holder 63 when the latter is in engagement with the support ill. Mounted upon the machine frame is a bracket 13 provided with a age block is which has a threaded tencn (Figure 3) extending through a bushing carried by the bracket 13, this arrangement forming a micrometer adjustment for the gage block 14 whereby the latter may be adjusted to a particular position for determining the amount of metal to be removed from the form tool bit or blank during a grinding operation. Thus by proper setting of the gage block E4, in contact with a template form 63 carried by the tool holder 60,

the form tool blank may be brought into engagement with the gage plate H and locked in position so that when the form tool is subsequently brought into engagement with the grinding wheel [8, only the desired amount of metal will be removed from the form tool.

In forming, grinding or resharpening form tools of the character shown at H in Figure 1, the relatively slidable member 3 3 is provided with a semi-spherically shaped tool holder support 78 which is also adapted to fit the recess El formed in the tool holder 60. The upper portion of member '35 is provided with a straight edge -80 which is arranged to operate as a gaging means or movement-limiting means for the tool holder 50 and tool bit 11 by reason of engagement of the template 63 therewith. The template B3 is removably secured to the tool and template holder BE and is held in position by means of a thumb screw Bi so that templates of other forms or sizes may be interchanged.

In grinding or sharpening form tools of the character shown at, it is usual to provide a relief angle I9 adjacent the cutting edge of the tool. In the apparatus illustrated, the member 34. adapted to carry the tool holder and template support 60, is vertically slidable through rotary movement of the hand wheel 43 so that the form tool Tl may be caused to engage the wheel [8 in different relative positions for varying the relief angle formed on the tool bit.

' Heretofore in grinding or sharpening form tools of very hard materials, as for example, tools formed from tungsten carbide alloys or other very hard metal alloys, it has been found that in using a grinding or abrasive wheel presenting a continuous surface, that the form tool of hardened metal tends to become burned and is not ground or sharpened so as to present a clean, sharp cutting edge. Moreover the ordinary abrasive or grinding wheel fails to effectively grind or out such hard tool and the surface of the wheel very soon becomes glazed and fails to function satisfactorily. In the present invention I have provided a method of configurating or abrading hard materials by utilizing a grinding or abrasive wheel l8 which is provided with a series of spaced grinding zones or elements for intermittent engagement with the tool to be ground. As particularly shown in Figures 1, 2, 4 and 5, the grinding wheel or unit I8 is formed with a plurality of radial recesses 84, which recesses divide the peripheral portion of the grinding wheel l8 into a plurality of circumferentially spaced segments or zones 85. The recesses 84 are of considerable radial depth so that the segments 85 have a useful life until worn to the depth of the recesses. The unit may be moulded of an agglomerate of abrasive particles held together by a suitable cement or bonding agent. In the use of the grinding unit I8, assuming the latter to be rotating in a clockwise direction as viewed in Figure 1 and counterclockwise as viewed in Figure 4, the edges 86 formed by the juncture of a wall of each of the recesses 84 and the peripheral arcuate surface of each of segments 85 are adapted to successively strike the tool bit 11. The recesses 84 are of a peripheral width greater than the thickness of the tool bit 11 so that during a grinding operation, while the operator is urging the tool holder 60 in a direction to bring the tool bit 11 into contact with th grinding wheel, the tool bit slightly enters each successive recess 84 as the same moves into registration with the tool bit so that the portion of the tool being ground or configurated is struck by each edge 86 of a grinding segment 85 during rotation of the grinding wheel. I have found that the rapid successive impacts of the grinding wheel segments with the portion of the tool bit to be formed or sharpened, very quickly and eificiently abrade or cut away the hard metal of the tool bit, providing a sharp cutting edge upon the form tool and without glazing th grinding wheel surface.

In the utilization of the method of my invention of grinding tools, means are provided for limiting the distance that the tool bit may move toward the grinding wheel during each grinding operation. This is an important feature of the invention for the reason that should the form tool bit be permitted substantial movement in a direction toward the grinding wheel, such excessive movement would permit the tool to move too I 8 deeply intoone or more of the recesses 84 which would result in damage to the grinding zones or segments and possible damage to the machine. I have found that in employing the method of my invention it is practicable to remove about five thousandths of an inch of metal from the tool bit at each individual grinding cycle or operation. To prevent excessive movement of the tool bit toward the wheel, the tool holder 60, bearing a tool bit 11 to be ground anda template 63 for controlling the form of the tool, is placed in cooperative relation with the support 10 of the gaging means. To adjust the tool bit for the removal of five thousandths of an inch of metal, the micrometer gage block or abutment 14 is rotated until it projects forwardly from normal position a distance of ten thousandths of aninch.

The template 63 is then caused to contact the gage abutment l4 and theform tool 71 re-adjusted by manipulation of the cam 65 and retaining screw 66 until the end of the form tool-is in contact with the abutment plate H. As the tool holder support Ill becomes in effect a fulcrumfor the tool holder support 60, and as the distance from the center of the support 10 to the'template 63 issubstantially twice the distance of the'center of the support 10 to the upper or cutting-edge of the tool bit 11, the tool bit-Will be in a position relative to the template so that five thousandths of an inch of metal may be removed when the tool bit is brought into engagement with the grinding wheel l8. After the tool bit H has been adjusted into contact with the abutment plate]! and the cam 65 brought into lockingengagement with the block 64, the holder 60 is transferred to the support 18 with the template 63 adjacent but out of engagement with the straight edge or template movement-limiting means as shown in Figure 1. With the tool holder in this position the operator exerts aforce upon the same in a direction toward the grinding wheel, bringing the tool bit into forcible engagement with the grinding wheel. .As the grinding wheel rotates,

the recesses 84 are brought into consecutive and rapid registration with the tool bit 1-1, the latter being projected slightly into each recess. This projection of the tool into the recesses positions the tool so that the edges 86 of the segments strike the nose of the tool and remove the metal from the tool by impact and without burning the metal. I have found that this action results in a smooth and sharp cutting edge being formed on the tool. The template 63 is in a position to engage the straight edge 80 to prevent the tool from moving into the recesses an abnormal amount. The successive impacts of the segments of the grinding wheel engaging the tool, very rapidly cuts away or removes the metal until all operative portions of the template 63 engage the straight edge 80. If a greater amount of metal is to be removed from the tool than may be accomplished at one operation, the operator transfers the tool holder 60 to the support 10 and readjusts the tool 11 into engagement with the abutment plate ll. After such re-adjustment is made, the tool holder 60 is again placed upon the support 18 adjacent the grinding wheel I8 and a further grinding operation effected to remove the desired amount of metal predetermined by the setting of the micrometer gage 14.

I have found that during a grinding operation, the tool holder 60 is vibrated to some extent by the successive impacts of the grinding wheel segments engaging the tool as the successive impacts tend to move the tool away from the grinding wheel, but the force exerted by the operator maintains the tool in a position to be continuously engaged by the wheel segments. As soon as the required amount of metal has been removed, the template 6.3 engages the straight edge and the vibrations of the tool holder cease by reason of the completion of a grinding cycle.

I attribute the successful operation of this method of grinding or configurating toolsto the fact that the tool is permitted to move slightly into each successive recess and that the impact of a grinding segment with the tool effects a more rapid and efiicient removal of the metal than does the engagement of a tool with an uninterrupted grinding wheel surface.

,Another form of apparatus for carrying out the method of my invention for removing hard metal from objects is illustrated in Figures 6 through 9 inclusive. As shown in Figure 6 the apparatus or grinding machine is inclusive of a base 90 having an enlarged receptacle portion 9I to receive the coolant or fluid directed against the grinding wheel 92 through a tube 95 connected to a fluid pump (not shown). The grindin Wheel 92 is of the so-called cup type and is inclusive of a metalbacking plate 93 which is mounted upon a suitable arbor 94 and rotated by driving means (not shown). The frame portion 96 of the machine is provided with two openings 91 and 98 providing two zones of access to the grinding wheel 92. The apparatus is provided with two arcuately-shaped members 99 carried by the frame 96 of the machineand each is provided with a semi-spherically shaped tool holder support I99. Each of the members 99 is adjustable about a center lying in a plane passing through the axis of rptation of the grinding wheel 92 and each may be selectively locked in an adjusted position by locking mechanism (not shown) manipulated by handle I9I Each member 99 is provided with a straight-edge or abutment plate I04 adapted to be engaged by a template carried by a tool holder of the same character as shown at 69 in Figure l. The adjustment of members 99 is for the purpose of obtaining various angles of relief for tool bits.

The grinding wheel as utilized in this form of apparatus is preferably fabricated of several individual abrasive or grinding units or segments I99 of the configuration shown in Figure 9. In the embodiment shown in Figures '7 and 8, eight abrasive units or segments I98 are employed which are spaced apart or separated by spacing members I9? to secure the units in spaced relation. The spacing blocks 191 are held in place by means of screws I98 threaded into openings provided in the backing plate 99. Each of the abrasive units I99 is provided with an inwardly extending projection H9 having an angularly disposed arcuate surface III. Means are provided for securing the units H16 in position on the backing plate, said means being in the form of an annular securing ring H2 which is formed with a peripheral surface I I4 angularlyarranged to fit the arcuate surfaces I II of the units or segments, as particularly shown in Figure .8. Theannular member I I2 is securely held to the backing plate 93 and in engagement with the units I96 by means of screws H5 threaded into suitable openings formed in the plate 99. As illustrated in Figures 6 through 9 inclusive I have found it preferable to use independent segments I99 suitably spaced for utilization with the grinding apparatus shown in Figure 6 for grinding hardened tool bits of the shown in Figure 4.

character shown at H 6 in Figure 8. It is to be understood that the tool bit H6 is carried by a tool and template supporting unit of the character shown at 60 in Figure 1. A cuptype wheel of a character adaptable for use with the apparatus shown in Figure 6 maybe used in which portions of the abrasive unit may be spaced through the provision of radial recesses formed in the grinding wheel in the same manner as in the wheel I8 However I have found it practical to utilize the form shown in Figures '7 through 9 inclusive for a cup-type wheel, for the reason that the independent units I96 may be quickly and easily replaced when the same have been worn down.

The principle of operation and method of grinding hardened tools on the apparatus illustrated in Figures 6 through 8 inclusive is the same as that employed in utilizing the apparatus illustrated in Figures 1 through 5 inclusive, i. e. an abrading'or removal of metal from the tool bit by impact of the edges ill of the units I96 when the abrasive unit is rotating in one direction, and the impact of edges N8 of units I96 when'the abrasive unit is rotating in the opposite direction. It is to be understood that the driving means for rotating the grinding unit in' the'apparatus shown in Figure 6 is of a reversible'character, so that the zones 9'! and 98 provide for use of diametrically opposed grinding positions on the cup wheel through the employment of a template and tool holder mounted upon either of the ball-shaped supports I09.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, the present disclosure is illustrative merely, the invention comprehending all variations thereof.

What I claim is:

The method of grinding a hardened formtool of the character described which includes advancing said tool by yielding pressure against a rotating grinding wheel having grinding zones spaced apart circumferentially a distance greater than the dimension of the tool in the direction of rotation of the wheel to cause thetool to engage said grinding zones and to enter the spaces between them in response to said pressure so that the leading edges of said zones by successive impacts with'said tool willvibrate the latter to remove metal from said tool by such impacts and by abrasion without objectionable burning of the tool or glazing of the wheel, and regulating the amount of metalrernoved-from said tool bypositively limiting the degree to which said'tool is advanced in the direction of said wheel by said pressure.

CLIFFORD L. GARRISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Bura May 8, 1945

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