US2238064A - Cutter grinding method - Google Patents

Description

A ril 15, 1941. c. E. KRAUS CUTTER GRINDING METHOD Filed May 16, 1958 4 Sheets-Sheet 1 v NvENToQ Char/es 15. 00 0418 PM .4m, 1%,. +7W.

fhmwsys A ril 15, 1941. c. E. KRAUS 2,238,064

CUTTER GRINDING METHOD Filed May 16, 1938 4 Sheets-Sheet 2 ?5 78 21 J4 54 32 .11 II 2e April 15, 1941. c, us 2,238,064

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CUTTER GRINDING METHOD Filed May 16, 1938 4 Sheets-Sheet 4 I NVE-NTOQ Patented Apr. 15, 1941 UNITED CUTTER GRINDING METHOD Charles E. Kraus, Rockford, Ill., assignmto The Ingcrsoll Milling Machine Company, Rockford, 11]., a. corporation of Illinois Application May 16, 1938, Serial No. 208,187

(Cl. 51---288l 6 Claims.

The invention relates to the art of grinding multiple blade rotary cutters adapted for face g or boring and more particularly to an improved method of and machine for grinding cutters having blades with edges difierent portions of which cut to different depths during u t ing of a work piece.

The quality of the surface finish produced by cutters of the above type is determined principally by the accuracy and uniformity with which the finally acting or finishing edge portions of the blades are ground. More particularly, the hing edge portions should all have the same surtace characteristics, should be of uniform length, and should be correspondingly spaced with extreme precision. It is also important that the initially acting or roughing edge portions as well as the intermediate edge portions he located accurately relative to the finishing edge portions.

it has been the practice heretofore in sharp euiug cutters of the above general character to git-had the blades successively, each blade being ground to finished form throughout its entire length before grinding the adjacent blade. It is mually necessary to dress and reset the grindiug wheel after each blade is ground. The dresstug and resetting introduces variations in the surt'ace characteristics and relative positions of the diderent cutting edges no matter how careiully and accurately it is done. These variations, however small, tend to produce unevenness in the finished surface of the work.

the primary object of the present invention is to provide an improved method of grinding cutters of the above general character with a higher degree of accuracy than has heretofore been practical, thereby enabling the cutter to operate at maximum efliciency and to produce an extremely true smooth finished surface on the work.

Uther objects and advantages will become ap-' parent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a side elevation partially in section at a grinding machine adapted for grinding rotary face milling cutters in accordance with the improved method.

Fig. 2 is an end elevation of the machine with parts broken away to show details of the adlusting mechanism.

Fig. 3 is a detail view of the slide locking mechanism.

Fig. 4 is a vertical section taken along the line 4-4 of Fig. 2.

Fig. 5 is a horizontal section taken along-the line 5-5 of Fig. 4.

Fig. 6 is a vertical sectional view of the grinding wheel dressing fixture.

' Fig. 7 is a vertical section taken along the line 'l--l' of Fig. 6.

Fig. 8 is a transverse sectional view taken along the line 8-8 of Fig. 6.

Fig. 9 is a fragmentary plan view showing the relative positioning of the grinding wheel and the cutter.

Fig.. 10 is a fragmentary sectional view through one of the cutter blades and its mounting showing the grinding wheel operating on the blade.

5 Figs. 11 and 12 are enlarged elevational vi ws of the edge portions of one of the cutter blades shown in Fig. 1d,

While the invention is suceptible of various 4,

modifications and may be practiced in various ways, I have illustrated in the drawings and will describe here in detail the preferred embodiment and method. It is to be understood, however, that I do not intend to limit the invention by such specific disclosure but aim to cover all modifications and alternative constructions and methods falling within the spirit and scope of the invention as expressed in the appended claims.

Generally stated, the invention contemplates the provision of means for adjustably supporting a grinding wheel, a wheel dressing tool, and the cutter to be ground so that the relative position oi the wheel and the edge portions of the cutter blades may be determined with a high degree of accuracy. More particularly, the various parts are so arranged that the wheel may be located with respect to a predetermined portion of the cutter as, for example, the plane of the finishing portions of the cutter blades. The grinding wheel is supported for reciprocation along the edge of one cutter blade. The dressing tool is supported at one side of the cutter being operated on and the grinding wheel is adjustable vertically and laterally to locate the active surface of the wheel very accurately with respect to the planes of the edge portions of the blades. Means is also provided for confining the relative traverse of the grinding wheel and cutter within accurately defined limits to insure uniformity in the length of the edge portions of the cutterblades.

By way of illustration, the improved method will be described as used in grinding a rotary face milling cutter of the type in which the various rows of edge portions are located in planes substantially parallel to the surface to be formed which planes are progressively stepped apart in a direction perpendicular to the surface. In the exemplary cutter, each blade is divided lengthwise into eight edge portions designated by the reference characters A, B, C, D, E, F, G, and H respectively. The corresponding edge portions are arranged in rows concentric with the axis of The edge portions B-H are spaced progressively outwardly in the manner illustrated.

The improved method, as applied to the sharpening of face milling cutters, contemplates the grinding of the corresponding edge portions of all of the cutter blades, that is, the edge portions forming one of the concentric rows in a single setting of the grinding wheel, then, after resetting the wheel, grinding the edge portions of the adjacent concentric row, and so on until all of the edge portions have been ground. In this operation, the edge portions projecting farthest above the surface of the cutter, that is, the finishing portions A are preferably ground first as the accurate location of these portions is most important. The grinding wheel is set at an effective height corresponding :to the edge to be formed on such portions and then passed across them individually in succession around the row without redressing or resetting the wheel. This insures formation of all cutting edges in the row precisely alike and in the same plane.

Since accurate vertical spacing of the edge portions is important in cutters of this character, it is desirable to locate the intermediate and roughing rows of edge portions with respect to the row of finishing portions. Accordingly, when the edge portions A have been ground, the grinding wheel is withdrawn for cooperation with the dressing tool. The dressing point of the tool is set so as to engage and dress the wheel lightly and then the wheel is given the final pass over the finishing portions of the blades so that the position of the dressing point will correspond exactly with the, cutting edges formed of this portion of each of the blades. Very little stock is removed from the cutter blades in this operation and there is consequently substantially no wear on the wheel.

The dressing fixture is provided with a micrometer gauge, preferably of the multiplying type, which may be set to zero indication after adjustment in the manner above described, thus facilitating resetting of the wheel for grinding the next row of edge portions. Ordinarily, the edge portions of adjacent steps are spaced apart extremely small distances. In the exemplary cutter blade shown in Figs. 11 and 12 of the drawings, the edge portions B constituting the second row are spaced .003' of an inch below the cutting edge of the finishing portions. The edge portion of the succeeding rows C to H are spaced successively .005,'.010, .015, and .020 of an inch below the next adjacent edge as illustrated. In order to grind the second row of edge portions B in proper relation to the finishing portions A, the point of the dressing tool is moved down the required distance, in the present instance .003 of an inch, as indicated on the micrometer scale of the tool. The dressing wheel is then lowered and passed over the dressing point, thus locating the effective grinding surface at exactly the right distance from the cutting edge formed on the previously ground portions A. The grinding wheel is then passed over the edge portions forming the second row B without changing the setting of the wheel or redressing the same. Thus, the edge portions of each blade are ground to absolute uniformity with all of these cutting edges lying in exactly the same plane entirely around the cutter.

The foregoing operations are repeated for each row of stepped edge portions, that is, the grinding wheel is accurately located by proper adjustment of the dressing tool and then the entire row of edge portions is ground without resetting or redressing the wheel. It will be understood, of course, that the rows of edge portions may be ground in the reverse order starting with the outermost row H'if desired.

Referring now to Figs. 1 and 2 of the drawings, the exemplary form of the machine for carrying out the method above described comprises generally a hollow rectangular frame or base l3 having a table I! for supporting a cutter iii to be ground, an adjustable supporting structure It for supporting a reciprocable grinding head I! in position for its grinding wheel It to operate on the cutter on the table [4, and a fixture I9 for holding a suitable grinding wheel dressing tool 20 in predetermined relation to the grinding wheel and cutter.

The table I is arranged to slide toward and from the grinding head on horizontal ways 2! on the base l3 to facilitate proper positioning of the cutter I 5 relative to the grinding wheel. Movement of the table is effected, in the present instance, by a hand wheel 22 acting through the medium of a shaft 23 having keyed thereto a pinion 24 which meshes witha rack 25 rigid with the table. A locking screw 26 of conventional construction is threaded into the side of the table and acts through a shoe 21 (Fig. 3) in engagement with the ways 2| to lock the table in set position.

Referring to Fig. 9, it will be observed that the cutter I5 is equipped with a plurality of removable cutter blades Iii arranged annuiarly around the face of the cutter. To facilitate the presentation of the different cutter blades in operative relation to the grinding wheel II, the cutter supporting table it is equipped with a rotatable fixture 28 for holding the cutter. As shown in Fig. 1, the fixture is formed with a depending cylindrical stud 29 journalled in a vertical bearing formed in the table I while the weight of the table is carried by anti-friction bearings 30 operating in annular raceways formed on the table and the fixture.

The supporting structure It is designed to provide a wide range of adjustment between the grinding wheel l8 and the table I to facilitate accurate positioning of the grinding wheel with respect to the cutter -to be ground and to adapt the machine for grinding cutters of various types and different sizes. The structure is aceordingy built up of a plurality of members adjustable one relative to the other whereby the grinding wheel may be shifted up or down and transversely of the axis of the table. The structure also includes means permitting reciprocation of the grinding head in a horizontal plane or. at an angle to the horizontal while the grinding wheel may be set with its axis at any desired angle to the reciprocatory path of the head.

In the preferred form of the machine illustrated, the supporting structure It comprises a knee 35 slidably supported on dove-tailed vertical ways 36 formed at one end of the base i3. For raising and lowering the grinding head, the knee ingly, the nut in rotating acts through the" threaded connection with the rod 4| to raise and lower the entire supporting structure It and with it the grinding head IT. A clamping screw 26" similar to the locking screw 25 is available for clamping the knee in set position.

Suitable means is provided for counter-balancing the weight of the supporting structure l6 to facilitate adjustment of the same. The counterbalancing means as herein shown includes a coiled tension spring 44 adjustably anchored at one end to a bracket 44 secured to the front wall of the base l3 and at the other end to a crank arm 45 fast on a rock shaft 45. Keyed to the rock shaft is a gear segment" meshing with a vertical rack 45 bolted or otherwise rigidly secured to the inner face of the knee 35. The weight of the supportingstructure is thus transferred to the spring permitting the structure to be raised or lowered with a minimum of effort.

The knee 35 is formed on its upper end to provide horizontal ways 41 extending transversely of the frame of the machine. Slidable on the ways 41 is a slide 48 carrying a frame 49 which supports the grinding head H for reciprocation. it hand wheel 50 is arranged to move the slide on the ways to position the grinding head with respect to the cutter blade to be ground. As herein shown, the hand wheel 50 is keyed or otherwise rigidly secured to one end of a screw ti rot-atably supported on the knee and confined against endwise movement in either direction by the hand wheel and a collar l abutting the ends of the bearing supporting the screw. The screw cooperates wtih a nut 52 formed on the lower side of the slide to move the slide in the ways when the hand wheel 50 is turned. The slide is equipped with the usual clamping screw 26 for locking the same against movement.

Referring more particularly to Fig. 2, the frame at as herein shown is generally of U-sliaped form and is provided at its intermediate portion with ways 53 to which is dove-taileda slide 54 carrying the grinding head ll. The frame is preferably pivoted at its forward end to the slide 48 lar position of the frame is effected by means of a screw 56 threaded into alug 56" on the slide and engaging with an abutment 51 formed on the underside of a transverse stiffening member 58 extending between the side portions of the frame. Formed on the side portions of the frame adjacent the rear end thereof are depending arms 59 having quadrant slots arranged to receive bolts 50 projecting laterally from brackets 6! on the slide 48. Nuts threaded onto the bolts maybe tightened to clamp the frame in set position.

The grinding head I! may be of any suitable construction and, as herein shown, includes a casing 62 enclosing a motor and suitable gearing for driving the wheel I8, A suitable guard 63 carried on the forward end of the casing 62 extends over and partially encloses the grinding wheel.

The grinding head I'l is preferably mounted on the slide 54 so as to permit the axis of the grinding wheel to be set at various angles to the axis of movement of the slide as shown in Fig. 9 to determine the clearance angle ground on the stepped edge portions of the cutter blades. For this purpose, the head is secured to the slide by means of a swivel connecting member comprising beveled edge plates 64 and 65 bolted or otherwise rigidly secured to the casing 52 and slide 54 respectively as shown in Fig, 4. The plates are arranged with their tapered edges in opposed relation and are encircled by a split clamping ring 65 having an inwardly opening V-shaped annular groove adapted to en ge the edges of the plates and clamp them tightly together. Such clamping is effected, in the present instance, by means of a screw 61 arranged to draw the ends of the ring together. To facilitate accurate positioning of the head, the ring is provided with a pointer 68 cooperating with a suitable scale 68 carried on the head.

The various adjustments to position the grinding wheel relative to the cutter to be ground are all made preliminary to starting the grinding operation. When the wheel has been properly set, it is passed over the cutter blade in grinding position by reciprocating the slide it. During this operation, the blade is held in proper relation to the grinding wheel by a finger fit adjustably mounted on the casing 62 and having one end projecting below the grinding wheel in position to engage the side of the cutter blade as shown in Figs. 10 and 12.

The means provided for reciprocating the slide comprises, in the present instance, a chain and sprocket mechanism enclosed within the frame 49 above the slide. As herein shown, this mechanism includes a suitable chain ll running over sprockets "l5 and I3 and secured to the slide as by a bolt 14. The sprocket 15 is carried on a horizontal shaft l2 journaled on the frame structure adjacent the forward end of the slide. The sprocket it is carried on a slide block 16 adjustably secured to the frame structure adjacent the rear end of the slide by a screw 'l'i. By turning the screw, the slide block and sprocket 13 may be moved toward or from the sprocket to adjust the tension of the chain and thus eliminate lost motion or back-lash. Fast on the shaft 12 is a hand wheel 18 for rotating the sprocket wheel 15 and thus imparting movement to the chain H, such movement being transferred to the head by the bolt 14 by which the chain is clamped against the slide. Thus, by rotating the wheel 18, the head may be reciprocated relative to the cutter IE to traverse the grinding wheel IB over the cutter blade with which it is associated.

In grinding intermediate edge portions of the cutter blades, it is necessary to confine the movements of the grinding head within accurately defined to prevent overrunning onto the next adjacent row of edge portions. Accordingly, novel means is provided for limiting the forward movement of the head which means is readily adjustable to condition the head for grinding successive rows of cutter edges.- As

'cally on the post 84.

herein shown, this means comprises a stop in the form of a bar 18 dove-tailed in a horizontal slideway 88 formed in an upwardly projecting flange or bracket 8| integral with the top wall of the frame 48. The slide 54 which carries the grinding head is formed with a stop engaging member 82 adapted to engage the stop 18 and thus limit the forward movement of the slide. To facilitate accurate positioning of the stop, the bracket 8| is graduated along its upper side edge to provide a scale 83 for cooperation with a suitable index point on the stop I8.

As herein before stated, the dressing tool 28 behind the cutter blade so that the wheel engages the suriace of the blade at an angle to the horizontal and grinds it with the proper clearance. The particular point at which the wheel and blade engage is determined by the setting of the finger 88 and may be adjusted as required. The head is next set at the proper angle with respect to its axis of reciprocation to grind the side edges 'of the stepped portions with the desired clearance angle. This adjustment is made by loosening the clamping ring screw 81 and turning the head'until the desired angle is indicated on the scale 88'.

Upon completion of the foregoing adjustments, the various parts are securely locked in set podtion and the grinding head is moved forwardly by the operation of the hand wheel 18 until the grinding wheel is in operative relation to the from the bracket is a post 84 (Figs. 6 and 7) car- 7 rying a sleeve 85 from which projects an exten the cutting point is moved up or down by reason of the threaded connection provided.

Mounted on the sleeve 85 immediately below the extension 88 is an indicating micrometer 88 preferably of the resetting type having a stem or feeler 8| projecting into the bore 81 and engaging with the lower end of the holder 88. Thus. when the holder 88 is screwed into or out of the bore 81, the changes in the position of the dressing point 28 are accurately indicated.

In order to confine the movements of the holder 88 within the limits of the indicator 88, the sleeve 85 is arranged to be adjusted verti- The sleeve is then locked in set position by means of a suitable clamping screw 82. Means is also provided for clamping the holder 88 in set position. As shown in Fig.

8. the clamping means comprises a pair of bushings 83 and 94 axially alined in a horizontal bore 94* in the extension 88. Adjacent edges of the bushings are beveled for cooperation with the holder 88. A screw threaded into the bushing 98 and having an enlarged head 85 cooperating with the bushing 84 serves to draw the bushings together and thus clamp the holder securely in set position.

The operation of the machine in grinding a stepped face milling cutter such as the cutter l5 shown in Figs. 9 and 11 of the drawings may be described briefly as follows. The cutter is placed on the fixture 28 and secured thereto in any suitable manner. The grinding head is then positioned for operating on one of the cutter blades I5 by shifting it laterally through the operation of the hand wheel 58. The position is dependent, of course, upon the angle of the cutter blade with respect to the radial axis of the cutter and will vary with difl'erent types of cutters. the adjustment of the wheel is such that the head in its reciprocation travels in a plane parallel to the longitudinal axis of the cutter blade.

As will be noted by reference to Fig. 10, the grinding head is positioned with its axis slightly In any case,

finishing edge portions A constituting the inner row of cutting edges. The grinding wheel is then lowered by turning the hand wheel 81 until it is in position to remove the desired amount of metal from the finishing portion of the blade and is locked in this position. The edge portion A of each blade is new ground by passing the wheel slowly over such portion. After each blade is dressedrthe head is retracted and the next blade is moved into grinding position by rotating the fixture 28. .The finger i8 locates the blade accurately with respect to the grinding wheel.

The above operation is repeated until all of the edge portions A have been ground to size. The grinding wheel may then be retracted and lowered slightly until it engages the dressing tool. Then, the wheel is passed over the edge portions A again, thereby taking a very light grinding cut insuring that all of the cutting edges will be ground to the precise setting of the dressing tool. The position of the wheel for grinding succeeding edge portions is determined with reterence to the cutting edges of the portions A.

Upon completion of the grinding of the inner row of edge portions, the wheel is retracted and the dressing point is lowered a distance corresponding to the vertical spacing between the edge portions A and B. This distance may be determined accurately by means of the micrometer 88. The grinding wheel is then lowered and dressed with the tool in this position after which it is passed over the edge portions B of all the cutter blades.

In order to avoid overrunning onto the previously ground edge portions A and to accurately locate the edge portion B with respect to the axis of the tool, the limit of forward movement of the head i1 is determined by the setting of the stop 18. This stop is adjusted with respect to the scale 83 and securely locked in position so that during the grinding operation, movement of the grinding wheel into engagement with the previously ground edge portions is effectually prevented. At the same time. the outer sides of the edge portions A are beveled oil. to avoid sharp corners and are relieved to provide the necessary clearance for proper operation. The beveling action is obtained through the use of a tapered grinding wheel as shown while the clearance angle is determined by the angular adjustment 0! t3: grinding head with reference to its supporting s e.

The foregoing operations are repeated for each row ofi edge portions 0-H until all have been groun 0 size. In each instance,

1 t in ge is determined 1231;12 :223: of the dressing tool 28 which may be effected very accurately by reason of the micrometer indicator provided. Since the dressing tool was initially set with reference to the plane of the finishing portions A, the succeeding edge portion will necessarily be properly located with respect to the first mentioned portion. Moreover, the edge portions will be of uniform length due to the action of the stop 19 which is set, of course, for each row.

The invention is applicable equally well to the sharpening of boring cutters having blades with edge portions stepped as above described to take successively deeper cuts in a work piece. For such cutters, a different fixture would be provided in order to locate the blade edges properly relative to the path of travel of the grinding wheel.

It will be apparent from the foregoing that with the improved method all of the blade edges are accurately located with reference to the finishing portions thereof and since corresponding edge portions of all the blades are ground by taking light cuts without redressing or resetting the tool, a high degree of uniformity is readily obtained. Moreover, by confining the movements of the grinding wheel within predetermined limits, the various edge portions of the blade are held to uniform length.

lBy reason of the wide range of adjustment, the machine may be readily adapted for grinding cutters of different types and sizes. The position of the grinding wheel may be adjusted with a high degree of accuracy so that the cutter blades may be ground to'a desired contour and with absolute uniformity throughout the entire group of blades. Further, the axis of the grinding wheel may be adjusted to provide any desired degree of clearance for the lateral edges of the various cutting areas of the blade.

I claim as my invention:

1. The method of grinding a rotary cutter having blades angularly spaced around the axis with roughing and finishing edge portions arranged in rows spaced progressively along and away from the cutter axis, which comprisesadjusting a grinding wheel to an effective position corresponding to that of the edges to be formed on the finishing portions of the blades, passing the wheel across the individual finishing portions successively around the entire row thereof, re-

adjusting the wheel to an effective position corresponding to that of the roughing portions of the blades, passing the wheel across the latter portions of the blades successively around the row thereof, and dressing the wheel only when it is readjusted.

2. The method of grinding a rotary milling cutter having generally radially extending blades each divided into a plurality of edge portions arranged in rows concentric with the cutter axis and spaced apart along the axis, which comprises adjusting a grinding wheel axially of the cutter to an effective position corresponding to the edges to be formed on one of the innermost row of edge portions, passing the wheel across the individual edge portions successively around the row thereof, readjusting the wheel axially of the cutter to an effective position corresponding to the edge to be formed on the adjacent row of edge portions, and passing the wheel across the edge portions of the blades successively around said adjacent row.

3. The method of grinding a rotary cutter having blades each divided into spaced edge portions arranged in rows concentric with the cutter axis, which method comprises setting a grinding wheel in an effective position corresponding to the edges to be ground on one of the rows of edge portions, passing the wheel across all of the edge portions of said one row successively, dressing and resetting the wheel to an effective position corresponding to the edges to be ground on the adjacent row of edge portions, passing the wheel across all of the edge portions of said adjacent row successively, and similarly dressing and resetting the wheel and passing it across the edge portions of the succeeding rows.

4. The method of grinding a rotary cutter having a plurality of blades each divided into elongated spaced edge portions spaced along and from the cutter axis with the corresponding portions of the different blades arranged in a row,

said method comprising adjusting a grindingwheel to an effective position corresponding to the edges to'be ground on one of the terminal rows of edge portions, passing the wheel across all of the edge portions of said one row successively, readjusting the grinding wheel to an effective position corresponding to the edges to be ground on the next adjacent row of edge portions, passing the wheel across all of the edge portions of said adjacent row successively, similarly adjusting the wheel and passing it across the edge portions of succeeding rows, and dressing the wheel in each of said adjustments.

5. The method of grinding a rotary milling cutter having a plurality of blades each divided into spaced edge portions extending generally parallel to the face of the cutter with corresponding edge portions of the blades arranged in rows concentric with the cutter axis, which method comprises setting a dressing tool in an eifective position corresponding to the edges to be ground on one of the rows of edge portions, passing the wheel over the dressing tool and then across all of the edge portions of said one row successively, resetting the dressing tool to an' effective position corresponding to the edges to be ground on the adjacent row of edge portions, adjusting the wheel for cooperation with the dressing tool in reset position, passing the wheel over the dressing tool and thereacross all of the edge portions of said adjacent row successively, and similarly resetting the dressing tool, adjusting the wheel and passing the wheel over the tool and then over the edge portions of each succeeding row thereof.

6. The method of grinding a rotary cutter having a plurality of blades each divided into elongated spaced edge portions with corresponding edge portions of different blades arranged in'rows, which method comprises adjusting a grinding wheel to an effective position corresponding to the edges to be ground on the row of edge portions which takes the final cut, passing the wheel across all of the edge portions of said one row successively, readjusting the grinding wheel to an effective position corresponding to the edges to be ground on the adjacent row of edge portions which takes the preceding cut, passing the wheel across all of the edge portions of said adjacent row successively, similarly adjust'ing the wheel and passing it across the edge portions of succeeding rows of edge portions until the row which takes the first cut has been ground, and dressing the wheel as a part of each adjustment.

CHARLES E. KRAUS.

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