US2160365A - Grinding machine - Google Patents

Description

y 1939- H. w. LARSSON 2,160,365

GRINDING MACHINE Filed Dec. 1, 1937 7 Sheets-Sheet l 0% INViNTOR. mu Bf ATTORNEY.

May 30, 1939. H. w. LARSSON 2,160,365

GRINDING MACHINE Filed Dec. 1 1937 7 Sheets-Sheet 2 INVENTOR.

ATTORNEY.

May 30, 1939. H. w. LARssoN 2,160,365

GRINDING MACHINE Filed Dec. 1, 1937 7 Sheets-Sheet 3 A TTORNEX H. RSSON GRINDING MAC E Filed Dec- 7 Sheet et 4 I' HI [NI/EN TOR.

. ATTORNEY Filed Dec. 1, 1937 7 Sheets-Sheet 5 INVENTOR.

MPZQW ATTORNEY,

May 30, 1939.

H. w. LARSSON GRINDING MACHINE l, 1937 '7 Sheets-Sheet 7 Filed Dec.

fie-55.12.

o 3 $3 g l e: 4 B 2 W l m x A r My INVENTOR. ZIia/zA hm W 4 ATTORNEY.

v Patented May 30, 1.93 9

UNITED STATES PATENT OFFICE 2,160,365 .GBJNDING mom Henry W. Larsson, deceased, late of Albany,

,Calif., by Josephine D. Larsson, executrix, Albany Calif Application Decemberl, 1937, Serial No. 177,625

9 Claims.

Reamers. milling cutters, and like metal cut-' ting tools as received from the factory are usually ground with a cutting clearance of five degrees.

'Ihis clearance may be decreased when usedon heat-treated alloy steel and may be increased for excessively soft steel. Cutting clearance is a function of-many variables. such as hardness and toughness of the material being worked upon, the cutting speed employed, table feed, the condition of the machine, etc., and canbest be determined by xperience and the particular work in 1-5- hand. All cutting tools of this character have a plurality of teeth, the front and outer ends of whichform the cutting es, and the clearance employed is determined when grinding the lands or the surfaces directly behind the cutting edges,

20 the lands usually being fiat or hollow ground. Hence, the greater the clearance employed, the weaker the cutting edge, as the backing which pports the cutting edge becomesless as the c earance increases, and the tool will accordingly 25 require frequent regrindihg. It might also be pointed out that two lands are usually employed, --to-wit,:-vprimary*land and an intermediate'land which are separately ground. The primary land is directly behind the cutting edge and is from 30 one-sixteenth t'o one-eighth of an inch wide, while the intermediate land .is much wider and is disposed on a greater angle to materially increase the clearance. In regrinding the cutter, three "operations are necessary, first, grind- 35 ing of the exterior surface to a true cylinder. secondly, grinding of the primary land, and third, grinding of the intermediate land. These sev- "eral operations take considerable time and are costly, as skilled operators are necessary.

The object of the present invention is to generally improve and simplify the construction and operationof grinding machines, and especially to provide a machine whereby a convex arcuate surface or single land is formed behind the cut- 45 ting-edges of a tool, as such a surface provides a gradually increasing clearance which does not materially weaken the backing behind the cutting edges of the teeth and which "furthermore does away with the primary and intermediate lands and reduces the-regrinding of a tool to one single operation? to provide means whereby the radius of the arcuate surfaces may be increased or decreased: to provide means whereby the final clearance produced by the arcuate surface may 55 be varied: and further, toprovide means where by an exact placement or position between the grinding wheel and each tooth to be ground is maintained so that uniform grinding of each tooth of a cutting tool will result.

In the drawings- Fig. 1 is a diagrammatic view showing the manner in which form cutters are ground;

ingthe standard method of grinding ters; I

Fig. 4 is a diagrammatic view showing the. grinding of profile cutters by the method forming the subject matter of the present applica-. tion;

' Figs. 5 and-6 are diagrammatic views shawing the efict of offsetting the dressing tool during the shaping or dressing of the peripheral face of the grinding wheel;

Fig. 'l is a perspective view of the grinding machine;

enlarged plan view of the grinding Fig. 8 is an head;

Fig. 9 is a front view of the grinding head, part of the column beingshown in section:

Fig. 10 is a side elevation of the grinding head looking in the direction of arrows X-X,

Fig. 11 is a side elevation of the grinding head looking in the direction of arrows XI-XI, Fi and 1 Fig. 12 is a vertical section of the column. and

the housing at the upper end thereof, said section also showing the spindle bearings and the spindle journaled therein.

The grinding machine forming the subject matter of this application isparticularly intended for grinding profile cutters such as multiple fluted, straight, or helical reamers, and milling cutters of varying shapes, except thattype known as form cutters" because the relief or land back of the cutting edges of a form cutter is preformed in the factory and is sharpened by simply grinding the frontcutting face of the tooth in a plane parallel to the axis of rotation as shown at I in Fig. 1. Profile cutters, on the other hand, are ground on the outer or land surfacesrearwardly of the cutting edges as shown at 2 and I in Fig.2, or as at 4 and 5 in Fig. 3, Fig. 2 showing a primary land 2 which is flat ground, and Fig. 3 a primary land which is hollow ground. The machine is not only intended for-grinding profile cutters, but also to form a new shape or form of land behind the cutting edge which will hereinafter be referred to as a radial or arcuate land, as shown at 6- in Fig. 4. Actual prac- Figs. 2 and 3 are diagrammatic views showtice has shown that the grinding of an arcuate land of the type shown in Fig. 4 provides a better backing for the cutting edge, causing it to stand up longer, and therefore requires less frequent resharpening, it reduces the tendency to dig in and chatter, and'produces a smooth finished surface and furthermore reduces the'time and cost of regrinding, as one single grinding operation is all that is-required to resharpen the tool as compared with the three grinding operations required when a tool is ground according to standard practice as shown in Figs. 2 and 3. The radial or surface ground behind the cutting edge of a tool bythe machine forming the subject matter of the present invention will be of increasing radius as the diameter of the cutter increases, and the clearance provided by the radial land or surface will vary in accordance with the character of the metal being worked upon; i. e., a hard steel or metal will require the least clearance and a softer steel a greater clearance. The radial land is of course imparted to a tooth by a grinding wheel, and in order that the grinding operation be as simple as possible and that it be completed in one operation, the outer edge of the wheel will be dressed or shaped to the exact contour or radius required.

One of the features of the present invention is accordingly that of providing a cutting or dressing means whereby the outer face of the grinding wheel may be properly dressed or shaped and maintained during a grinding operation. Another important feature is the provision of means whereby an exact placement or position between the grinding wheel and each tooth is maintained so that the radial land or surface ground behind the cutting edge of each tooth will be exactly the; same. of the invention will be more. clearly understood,

a detailed description of the c'onstruction and operation of the machine will be submitted.

Referring to Figs. 7 to 11, inclusive, l8 indicates a pedestal or base upon which is mounted a work supporting table H. the top of the base at the rear of the table II is a column l2, and secured on the upper end thereof is a housing M which functions as a sunport for a grinding head generally indicated at B. -.Two vertically disposed guideways l5 and I6 form an integral part of the housing. Mounted on the guideway I6 is a slide plate ll'and car- 'ried thereby is a secondary slide plate 18 to which is fixed a bracket is upon which is slidably mounted a carriage 28. The plates l1 and 18 are vertically movable on the guideway it through means of a hand wheel 2| and a screw feed rod 22 actuated thereby, said screw rod extending through a nut 23 fixed to the guideway ii so that when the rod is rotated, vertical movement will be imparted: The secondary slide plate It, while movable in unison with the plate I1, is also movableindependently thereof, as a shaft 24 which is provided with a turn knob 25- is journaled in the slide plate It and carries'a small gear 26 which meshes with a gear rack 21 secured on-tli'efaceof the plate I'I. A The bracket I9 is also provided with a guideway upon which thezcarriage 20 is slidable crosswiseof the bracket or, in other words, to or away from the slidev plates l I and IS. A screw feed operated by a turn knob 28 similar to that described in connection with the plate I1 is em-' ployed to transmit the movement; The purpose of the movable and carriagewill hereinafterbe described.

In orderthat these and other features Extending through '2i and the screw feed or rod 22.

Extending through the housing centrally between the guideways Ii and II is a spindle 2!, on the outer end of which is mounted in the usual manner a grinding wheel 30. The spindle and the wheel attached thereto may be driven in any suitable manner, for instance, by a pulley 3| which is belt driven. as shown in Fig. 12, and bearings 32 and 23 are provided for its sup- P The carriage 20 functions as a support for a diamond cutter 35 whereby the outer peripheral face of the grinding wheel is shaped or dressed, and as one of the features of the machine is the grinding of radial contours in back of the cutting edges of the teeth of cutting tools such as milling cutters, reamers, etc., a mounting must be provided whereby the cutter 35 may be moved across the face of the grinding wheel to dress it to the radial surface or contour required. This is accomplished as follows: Suitably securedto the upper surface of the carriage 20 is a bearing 36 in whichis supported a sleeve 31 which is provided with a knob 314 on its outer end. The

sleeve is longitudinally movable in the bearing for purposes hereinafter to be described, and its movement is limited by a pin 38 projecting into a groove 39 formed in the upper surface of the sleeve, said pin-and groove also securing. the sleeve against rotation'in the bearing. While the sleeve is longitudinally movable, it is nor-* mally clamped and secured against longitudinal movement as one end of the bearing is slotted longitudinally as shown at 40, and is actuated by a clamping lever ll. Extending through the,-

sieeve is a rod 42, the outer end of which is provided with a turning knob 42, while the inner end carries a holder 44 through which extends at right angles "to the rod a cutter bar II on the inner end of which is mounted the diamond cutter 35. The bar is secured in the holder by a set screw 46, said screw also permitting,- justmentof the bar to increase or decrease the radial arc or sweep of the cutter I i. The rod 42, 7 together with the holder' and the cutter bar extending therethrough, is always free for rotational movement with relation to the sleeve 36, but such movement is limited by a pin 41 in the holder which engages opposite ends of a I shoulder 48 formed on the inner end of the sleeve.

sharpened, and the contoured face of the grindling wheel. The steady rest finger is indicated at so and isadlustably secured asst II in the lower end of an arm 52 which in turn is adjustably seemed as at 53 to a slide plate I4 vertically movable on the guideway IS. The sliding plate IT, as previously stated, is moved vertically on the guideway It by means of the hand wheel is transmitted to the slide plate [4 through means of a gear 55 which is :I'ciurnaledon and freely rotatable aboutthe inner' spindle bearing. The gear is in continuous mesh with 'gear racks H and 51 secured to the respective sliding pistes l1 and 54. Thus, if the plate I1 is moved downwardlyto bringthedimondcutterfl closer to This movement tain'ing a constant relative position between the 40 across the face of" the grinding wheel between the dressing tool and the. steady rest finger, and at the same time a fixed predetermined position between the contoured face of the grinding wheeland the teeth of the tool ,to be ground.

In actual practice, the face of the grinding wheel will have to be dressed or reshaped for each milling cutter or reamer to be ground, 1. e., if

their diameters vary, as the radial contour will vary in proportion to the exterior diameter of the tool to be ground. For instance, if a milling cutter such as shown at III in Fig. 7 is to be measured, and if the diameter is two and three-,

quarters inches, the radius of the contour will be one-half that, or one and three-eighths inches. Knob 25 is then grasped and rotated until the "0 mark on the sliding plate I. registers with one and three-eighths inches on the scale indicatedat H (see Fig. 10). This operation'raises the carriage together with the diamond cutter or dresser to a point one and three-eighths inches above a setting plate '12 .(see Figs. 9 and 11). The clamping lever 4l is then released sleeve 31 is grasped by the knob 31a, and pulled outwardly until stopped by pin 38, at which point the cutter bar will align with the setting plate 12. The set screw 44 is thenlreleased and bar 45 is pushed downwardly in the holder 44 until the diamond cutter or dresser 35 rests on the setting plate, set screw 46 is again tightened to secure the bar, and sleeve 31, which supports the holder and cutter bar, is then pushed back to normal position where it'is again stopped by pin.

38 and again clamped by the lever 4|. In this position the cutter bar is swung back and forth limits established by the pin 41 and the opposite ends of the shoulder 48 which it contacts, and as .the radius of swing is one and three-eighths inches, the face of the wheel will bedressed or 45 contoured to'a radius of one and three-eighths inches.

By referrihgto l0 itwill lie-noted that the bracket supporting the carriage 24 carries a graduated scale 1|, and the carriage a 0 mark.- If the 0" marks on the scale and carriage'register while the face of the grinding wheel is being dressed the tool to be .ground will have no clearance behind the cutting edges of the teeth, as a true cylindrical surface having a radius of one and three-eighths inches will result, as diagrammatically illustrated in Fig. 5. On the other hand, if the carriage II is moved by means Lof its screw feed in a direction toward the slideflplate it, a radial contour .will be formed on the face of the grinding wheel such as shown in Fig. 6, which will give 'a clearance. Each graduation on scale It represents a clearance .of .002 of an inch, and if the carriage is moved to the pdsition shown in Fig. 10, a clearance of .004 of an inch will result as the "0 mark registers .withthe second graduation beyond the 0" mark on the scale. Any clearance may be given, but the range of, the scale shown at I2 is .012, as six' gradug, tions are provided. To further illustrate the manner in which clearance is obtained reference will be made to Figs. 5 and 6. The radial dimension of the milling cutter shown at ll is one and three-eighths inches, -If.a compass is placed at the center I! of the cutter, and a circle is drawn with a one and three-sights radius, the

dicated at 82, thereby providing a clearance behind ,the cutting edges of the teeth which gradually increases and assumes the greatest dimension at the rear of the teeth as indicated at. In other words, the effect of adjusting or moving the carriage toward .the. slide I8 is just the same as offsetting the centers 19. and ill in Fig. 6, the result being that the greater the offset the greater the final clearance on the teeth being round.

. After the grinding wheel has been dressed, the milling cutter I0 is secured on the arbor (see Fig. 7) which is supported between the head and tail stock of a carriage mounted on the'work supporting table. The whole grinding head is then lowered to grindingposition bylowering the column which-supports the grinding head through means of'a screw feed actuated from the.

front of the pedestal by a hand wheel 86. With the steady rest finger in proper position, the face 81 of a tooth (see Fig. 10) is brought against the finger and the carriage on the work supporting table is then moved back and forth under the I grinding wheel. Each tooth is thus ground in successive order and if a second or third grind is necessary to impart the proper contour and complete sharpening, the operation is merely repeated. Inasmuch as an exact ,pomtion is maintained between the contoured surface of,

the' grinding wheel and each tooth to be ground,

by means of the steady rest finger, and in view of the fact that the dressing tool or cutter 35 rest finger, the tooth to be ground, and last but not least the contoured face of the grinding wheel.

Once a milling cutter, reamer, or similar tool v has been ground or sharpened in the manner,

here described, the grinding operation when resharpening is easily and quickly accomplished as only one face of each-tooth is ground, and one set-up and grindcompletes the job. Due to the fact that the steady rest finger and the diamond cutterflor dresser are inter-connected and move in unisongtheir relative position with relation to the face of the grinding wheel never changes, and uniform accurate grinding of tools results. By this method of shaping and grinding the teeth of a tool, more stock is left directly behind the cutting edges to support and back them up with the result that the cutting edge stands up longer and requires less frequent resharpening. Also, it has been found that the tools when ground as here described have less tendency to dig in and chatter, and that a higher finished and almost polished surface is obtainable,

particu-.- larly with a finishing. reamer.

In actual operation, the best clearance'for any particular job is found by practical experience,'and once this has-been established, a

written record thereof is made so that any tool may be reground with that particular clearance, this being possible as scales are provided which permit resetting ofthe diamond dresser-to produce an exact duplicate regrind of the tool."

Having thus described the invention, what is claimed and desired to secure by Letters Patent 1. In a grinding machine of the character described, a grinding wheel, a dresser bar with a cutter member at one end thereof, a pivotal support for the dresser. bar to permit swinging of the bar and cutter member across the peripheral face of the wheel to cut a radial contourin the face thereof, means for raising or lowering the pivotal-support to permit cutting of radial contours of varying radial dimensions, a steady 'rest finger disposed adjacent the wheel, tomaintain apredetermined position between each-tooth of a tool to be ground and the contoured face of the grinding wheel, and means for moving the cutter bar and steady rest finger in unison to and away from the contoured face of the wheel.

2. In a grinding machine of the character de-' scribed, a grinding wheel, a dresser bar with a cutter member at one end thereof, a pivotal support for the dresser bar to permit swinging of the bar and cutter member across the peripheral face of the wheel to cut a radial contour in the face thereof, means for raising or lowering the pivotal support to permit cutting of radial contours of varying radial dimensions, means for laterally adjusting the cutter bar with relation -to the wheel to further vary the radial contour cut in the face of the wheel, a-steady rest finger disposed adjacent the wheel to maintain a predetermined position between each tooth of a tool to be ground and the contoured face of the grinding wheel, and means for moving the cutter bar and steady rest finger in unison to and away from the contoured face of thewheel.

3. In a grinding machine of the character described, a grinding wheel, a pivotally mounted dresser bar having a cutter member at one end thereof disposed adjacent the wheel and adapted to swing crosswise of the peripheral face of the wheelto cut a radial contour in the face of the wheel, a steady rest'finger also disposed adjacent the wheel to maintain a predetermined position between each tooth of a tool to be ground and the contoured face of the wheel, and means for maintaining a constant relative position between the cutter bar and the steady rest finger.

4. In a grinding machine of the character described, a grinding wheel, a pivotally mounted V dresser bar having a cutter member at one end toured face of the wheel.

5. In a grinding machine of the character described, a grinding wheel, a pivotally mounted dresser bar having a cutter member at one end thereof disposed adjacent the wheel and adapted to swing crosswise of the peripheral face of the wheel to cut a radial contour in the face of the wheel, a steady rest finger also disposed adjacent the wheel to maintain a predetermined position between each tooth of a tool to be ground and the contoured face of the wheel, means for moving the cutter bar and-steady rest finger to and away from the contoured .face of the wheel,

1g and a connection between them whereby when they are moved they will move in unison and an equal'distance.

6. In a grinding machine of the character described, a main base, a grinding head mounted thereon, a spindle supported grinding wheel journaled in the head, a pivotally mounted cuttenbar mounted on the head and adapted to be swun across the peripheral face of the grinding wheel tocut a contoured face therein, a work supporting carriage on the base to receive and support a tool to be ground, means for moving the head to and away from the tool to be ground, means for increasing or decreasing the radial length of the cutter bar with relation to its pivotal support, a steady rest finger carried by the head and engageable with the teeth of the tool on the carriage to maintain a predetermined position between the contoured face of the wheel and the teeth of the tool while they are being ground, and means on the head for maintaining a-constant relative position between the cutter bar and said finger.

-7. In a grinding machine of the character described, a grinding wheel, a dresser bar having a cutter member at one end thereof, a holder in which the dresser bar is adiustably securedto lengthen or shorten'the distance between the holder and cutter member, a pivotal'support for .the holder to permit the cutter member to be swung across the peripheral face of the grinding wheel to cut a radial contour therein, a setting plate disposed at one side of the grinding wheel, means for moving the dresser bar and cutter member into alignment with the setting plate I when the radial swing of the cutter member is to be changed, means for releasing the dresser bar with relation to the holder to permitthe cutter member to rest in the setting plate, and means for raising or lowering the holder to lengthen or shorten the radial swing of the cutter" member.

8. In a grinding machine of the character described, a grinding wheel, a dresser bar having a cutter member at one end thereof, a holder in which the dresser bar is ,adjustably secured to lengthen or shorten the distance between the holder and cutter member, a pivotal support for the holder to permit the cutter member to be swung across the peripheral face of the grinding raising or lowering the holder to lengthen or shorten the radial swing of the cutter member, and a graduated scale with relation to which the holder moves so that the radial swing of the cutter member may be measured and indicated.

9. In .a'grinding machine of the character described, a main base, a grinding head mounted thereon, a spindle supported grinding wheel journaled in the head, a carriage on the head, a bearing on the carriage, a sleeve in the Bearing, a rod in the sleeve, a holder on one end of the rod, a

cutter bar extending through the holder and having a cutter member at one end thereof, said rod and holder forming a pivoted support for the where the cutter member aligns with the setting plate, releasable clamping means on the holder to permit the cutter bar to be moved in the holder until the cutter member rests on the setting plate, means for raising or lowering the carriage together with the bearing, the sleeve, the rod and the holder to lengthen or shorten the radial swing of the cutter member, said clamping means on the holder being clamped when the cutter bar is ID adjusted and said sleeve, rod, holder and cutter bar being moved longitudinally in the bearing back to the grinding wheel after the cutter bar is clamped, and means for clamping the sleeve in the bearing, said clamp leaving the rod and the holder free to swing the cutter member across the face of the grinding wheel.

JOSEPHINE D. LARSSON} Executria: of the Estate of Henry W.- Lars-son,

' Deceased.

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