US2914888A

US2914888A - Bit grinder

Info

Publication number: US2914888A
Application number: US643966A
Authority: US
Inventors: Thomas F Mcdougal; Waldo R O'dell
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-03-05
Filing date: 1957-03-05
Publication date: 1959-12-01
Anticipated expiration: 1976-12-01

Description

Dec. 1, 1959 T. F. MODOUGAL ETAL 2,914,888

. l/Mda/BWe/l ATTORNEYS Dec. 1, 1959 T. F. MGDOUGAL ETAL 2,914,888

BIT GRINDER Filed March 5, 1957 8 Sheets-Sheet 2 IN VENTORS iimsZJ/Mazyml 1 ilk/M15204! 827W Fm ATTORNEYS Dec. 1, 1959 T. F. M DOUGAL ETAL 2,914,388

. BIT GRINDER Filed March 5, 1957 8 Shasta-Sheet 3 INVENTORS flmmwwww BY M1012 flde/l W UzZ/JW ATTORNEYS Dec. 1, 1959 T. F. MCDOUGAL ETAL 2,914,888

BIT GRINDER 8 Sheets-Sheet 4 Filed March 5, 1957 1N VENTORS [firms [fl/J0 BY w ) ATTORNEYS Dec. 1,1959 T. F. MODOUGAL El'AL 2,914,888

BIT GRINDER Filed March 5, 1957 8 Sheets-Sheet 5 Jy/z INVENTORS J w Wfimm ATTORNEYS Dec. 1, 1959 T. F. M DOUGAL ETAL BIT GRINDER 8 Sheets-Sheet 6 Filed March 5, 1957 INVENTOR8 Dec. 1, 1959 T. F. MCDOUGAL ETALY 2,914,838

BIT GRINDER 8 Sheets-Sheet 7 Filed March 5. 1957 INORS 720M311 al%' I/Mdall. 0M?

Dec. 1, 1959 'r. F. MODOUGAL EIAL 2,9 ,3

BIT GRINDER 8 Sheets-Sheet 8 Filed March 5, 1957 Hamil/M WWI.

United States Patent BIT GRINDER Thomas F. McDougal, Fairmont, and Waldo R. QDell, Fairview, W. Va.

Application March 5, 1957, Serial No. 643,966

20 Claims. (Cl. 51-46) This invention relates to grinding machines, and particularly to grinding machines adapted to sharpen bits of saw chains of the type used in mining operations.

The principal object of the present invention is to provide a grinder which will properly shape bits having rounded ends, and perform this operation automatically in a series of steps, whereby a plurality of bits may be in various stages of grinding simultaneously on the same machine.

A more specific object is the provision of such a machine wherein the grinding operation is a result of the combined movement of the bit being ground and the grinding member, to provide proper contour to the bit and prevent undue Wear to the grinding element.

Another object of the invention is the provision of bitholding and controlling means to cause the bit to be oscillated about the center from which the curvature of its end is struck during grinding operations and be held against oscillation during travel between grinding stations.

A further object of the invention is the provision of grinders which will make predetermined traverses of the bit during grinding under predetermined pressure, and move away from the bit when the bit is to be indexed.

Still further objects include the provision of novel bit positioning means, novel grinding element mounting and novel indexing mechanism.

Other objects of the invention will appear from the following description of one practical embodiment thereof, when taken in conjunction with the drawings which accompany, and form part of, this specification.

In the drawings:

Figure 1 is a front elevation of a bit grinding machine embodying the principles of the present invention;

Figure 2 is a side elevation of the machine, parts being broken away to show interior mechanism;

Figure 3 is a top plan view of the machine;

Figure 4 is a vertical transverse sectional view through the upper portion of the base of the machine, taken on the line 44 of Figure 2 and on an enlarged scale;

Figure 5 is a fragmentary vertical section through the mounting for one of the grinders and is taken on the line 5-5 of Figure 3;

Figure 6 is a side elevational view of the grinder mounting mechanism shown in Figure 5;

Figure 7 is a vertical section through a grinder pivot and is taken on line 7-7 of Figure 6;

Figure 8 is a horizontal section through the base of the machine taken on the line 8-8 of Figure 1, illustrating the grinder lifting mechanism;

Figure 9 is a vertical section through the upper portion of the base of the machine taken on line 99 of Figure 8;

Figure 10 is a fragmentary vertical sectional view taken on line 10-10 of Figure 9, showing the grinder lifting rack and associated mechanism.

Figure 11 is a' fragmentary vertical sectional view taken on line 11- -11 of Figure 9, showing further details of the grinder lifting mechanism;

ice

Figure 12 is a horizontal sectional view through the upper portion of the base of the machine showing the driving means, the bit holder guide track and associated mechanism for controlling the rotatable turret; and

Figure 13 is a perspective view of means for oscillating the bull gear which governs the bit holder guide track.

In general, the invention concerns a fully automatic bit grinding machine. Bits are placed in bit holders and moved sequentially to a plurality of grinding stations. At each station the bit holders are oscillated to grind rounded ends on the bits, while the grinders have a traversing motion to prevent spot wear. Means are also provided to insure proper positioning of each 'bit in its holder for accuracy in grinding.

Referring to the drawings in detail, there is shown a bit grinding machine consisting of a cabinet base 1, which carries a turret 2 movable intermittentlyto carry a plurality of bit holders 3 mounted thereon sequentially to a loading station 4, a plurality of

grinding stations

5, 6, 7

, and 8 and an unloading station 9. At each of the grind ing stations, grinders 10 are mounted.

The base is formed as a heavy housing 11, having a lower horizontal partition 12, supporting certain of the mechanism, and an upper partition 13 supporting the bit holder oscillating mechanism and turret indexing mechanism. Near the upper rim of the base an annular support 14 is mounted to carry an upstanding ring 15. The turret 2 is mounted upon a central shaft 16 which is journalled in a bushing 17, fixed to the upper partition 13. The shaft and the ring 15 guide the turret during its step by step rotative movement.

The turret is provided with six openings 18 equi-spaced around it near its periphery for mounting the bit holders 3. This will permit simultaneous positioning of the bit holders at the loading, four grinding and unloading stations.

The bit holders are all identical, so'only one will be described. It consists of a sleeve 19, to fit within an opening 18 of the turret, and having an external annular shoulder 20 to rest upon the turret to position it vertically. A cap member 21 fits over the sleeve. Near the top and bottom of the interior of the sleeve there are bearings 22 and 23 to rotatably mount a shaft 24. Shaft 24 is of sufiicient length to extend above the cap 21 and below the bottom of the sleeve. An arm 25 is fixed to the lower projecting end of the shaft 24 and a second arm 26, which forms the bit holder proper, is fixed to the top projecting end. The arm 25 carries a guide roller 27 at its outer end to control the motion of the bit holder, as will be described.

Arm 26 is bifurcated and extends outwardly from shaft 24 to form a pair of upstanding ears 28. A pin 29 extends between the ears at their ends and pivotally mounts a bit clamping lever 30 upon the arm 26. The lever is of inverted L shape, forming a depending operating arm 31 and an overhanging bit-engaging jaw 32. Pivotal movement of the lever will move the bit-engaging jaw toward or away from a bit seat 33 held between the ears 28 of the arm 26 by means of pins 34. A bit in position upon the seat 33 will actually be engaged by an adjustable stud 35 which is threaded through the bit-engaging arm 32 and held in positions of adjustment by means of a lock nut 36. The movement of lever 30 is controlled by a toggle which consists of an arm-r37 pivotally connected to one end of a spring, loaded link 38 having its opposite end pivotally mounted in the lower end of the tion, .as viewed at the right of Figure 4, the toggle will be broken and lever 30 rockedin a counter-clockwise direction around its pivot 29 raising the bit-engaging jaw 32 to release the bit. An opposite movement of handle 41 will bring the toggle members into alignment and exert spring load pressure against the lever 39 to hold the bit in place upon the seat. It will be evident that the toggle is self-locking to hold the bit clamp in its two positions.

As mentioned above, the turret carries the bit step by step to each of the several stations. This is accomplished by means of an indexing mechanism 42. The indexing mechanism is mounted upon the shaft 16.

The indexing mechanism includes a pawl arm 43 fixed to the top of shaft 16 to rotate with it. At its outer end the pawl arm carries a pawl 44 which is pivotally mounted on the end of the arm and has a roller 45 positioned to follow the surface of indexing cam 46. Cam 46 is so designed that it will cause the pawl 44 to swing radially outward at one point during the revolution of shaft 16, remain in its outer position while traveling through an arc of approximately 60 and then permit the pawl to retract to its original position. The pawl is provided with a nose 47 designed to engage sequentially pins 48 which are fixed to the under side of the turret 2. The pawl, when it is in its extended position, will engage a pin and move it forwardly, thus indexing the table through an are equal to the spacing between the respective stations. As the next succeeding pin 48 comes into the position which the previous pin occupied when contacted by the pawl 47, it is engaged by a latch 49 pivotally attached to a fixed section of a guide track 50 secured upon the horizontal partition 13. The guide track will be described in detail hereinafter. Latch 49 is urged toward pin engaging position by means of a spring 51 having one end connected to the latch and the other end fixed to the indexing cam 46. The latch is provided with a cam surface 52 which is engaged by pins approaching locking position so that the latch will be moved outwardly. As soon as the pin passes off of the cam surface 52 the latch springs inwardly to engage the pin and hold the turret immovable. The latch is also provided with a cam surface 53 engageable by the nose 47 of the pawl 44 so that as the pawl moves outwardly during its rotation it will withdraw the latch from the pin which it had engaged so that the turret is free to be rotated. Continued rotation of the pawl will move the turret as previously described.

It was mentioned above that pawl arm 43 is fixed to shaft 16 and rotates with it. The shaft is caused to rotate by motor 54 which is mounted upon a tiltable bracket 54 pivoted to the base housing as at 55. A threaded adjustment screw 56, operative by means of the knob 57, permits tilting of the platform and consequent bodily movement of the motor. The motor carries a variable pitch pulleySS which is connected by means of a belt 59 to the pulley 60 of a gear box 61. The motor is adjusted by the knob 57 to change the speed output. Gear box 61 has a vertical output shaft fitted with a driving spur gear 62. This gear meshes with a large gear 63 which, with oscillating cam 64 and traversing cam 65 joined as a unit, is mounted on shaft 16. Thus, shaft 16 will be in constant rotation during operation of the machine and pawl arm 43 of course will be in continuous movement. It will be evident, therefore, that shaft 16 will make one complete revolution for each indexing movement of turret 2.

As the turret indexes, the bit holders will be moved from station to station and will present the bits to the several grinders. During this movement, the bits are held stationary and during the dwell at each station the bit holders are caused to oscillate so as to grind the proper curvature on the bit. This is accomplished by means of the guide track fixed in part upon the upper partition 13 and in part upon a plurality of spur gears 66. The guide rollers 27 on the bit holder control arms 25 ride inthe track 50.

The track is composed of a number of sections. One section 67, of fairly large extent, is fixed to the partition 13 and controls the position of the bit holders at the unloading and loading stations. The shape of this section of track and its distance from the axis of the turret is such that the bit holders will assume positions at these stations substantially parallel to the front of the machine, as shown in Figure 12. One of the spur gears 66 will be mounted beneath the turret upon a partition 13 adjacent each of the grinding stations. The axes of the gears will be in vertical alignment with the axes of the pivot shafts 24 of the respective bit holders when at the various grinding stations. Each gear carries an arcuate section of track 68, fixed to the gear and rotatable therewith. Short sections 69 of track are mounted on partition 13 intermediate the gears.

From Figures 4 and 12 it will be obvious that due to the concentric positions of the gears and bit holder pivot shafts 24 at the various grinding stations and the offset position of the guide rollers 27 in the track sections 68, oscillation of the gears will cause similar and simultaneous oscillation of the bit holders. In order to oscillate the gears, a bull gear sector 70 is provided, mounted for free rotation about the bushing 17 and in mesh with the spur gears. Oscillation of the bull gear sector will cause simultaneous oscillation of all of the spur gears.

Bull gear sector 76 is moved through rotation of cam 64 which is fixed to the drive shaft 16 as described. Cam 6 is designed to provide two cycles of oscillation and a period of dwell for the bull gear sector 70 for each rotation of the drive shaft 16. The cam 64 is provided with two rises 71 and '72, which control oscillation, and an arcuate portion '73 concentric to the shaft 16, which controls the dwell. Cam 64 is so oriented with respect to indexing cam 46 that the non-operative dwell of the bull gear sector 70 will occur during indexing movement of the turret 2. Thus, all sections of the track will be stationary and in end alignment when the turret 2 indexes.

Movement is transmitted from cam 64 to the bull gear sector 76 through lever 75 and link 76 to a gear sector '77 which is in mesh with a gear 83 mounted beneath partition 13 on the shaft 84 of one of the gears 66. Lever 75 is pivotally mounted, as at 78, and carries-a cam follower roller 79. A spring 80, connected to the free end of gear sector 77, holds roller'79 in contact with cam 64.. Link 76 is mounted in a slot 81 arcuately extending along gear sector 77 so that the link may be adjusted to vary the throw of the gear sector. A pin 82 projects downwardly from the partition 13 to limit the throw of the gear sector. Thus, it will be clear that as the cam 64- rotates, the bull gear sector 70, spur gears 66 and bit holders 3 will oscillate twice through a predetermined arc while the bit holders 3 are at the grinding stations, and the gears 66 will remain stationary while the turret 2 indexes, carrying thebit holders 3 to the next station.

At each of the grinding stations, there is a grinder 16, as mentioned above, each consisting of a motor 85 having a grinding wheel 86 connected to its shaft 37. The motor is housed, and a housing 88 surrounds the grinding wheel except for that portion facing the bit holders. The grinders are mountedfor vertical traversing movement during grinding as well as vertical lifting and outward swinging between grinding periods.

Each of the grinder motors is pivotally hungfrom a lever 89 by means of a shackle 90. The shackle is rigidly connected to the motor housing so th'at'the motor and shackle may move as a unit about the pivotal connection 91 between the shackle and the lever 89. Lever 89 is pivotally connected at one end, as at 92, to a hanger 93 mounted. upon an arm 97 which extends radially to the turning axis of the turret 2. There is an arm 97 for each grinder. The arms 7 form part of a superstructure which includes mounting arms 95 which are integral with the arms 97 and connected at their ends to the tops of supportingposts 96; Posts 96have,

their bases secured in the annular support 14. Each arm 97 is slotted longitudinally to receive the body portion 98 of the hanger 93. Horizontal flanges 99 extend to the sides of the body portion of the hanger to underlie the side rails of the arms 97. A screw 100 and washer 101 serve to clamp the upper surfaces of the flanges 99 against the bottoms of the side rails of arms 97. Hangers 93 are capable of adjustment so that the grinding wheels may be moved inwardly as wear occurs. This is accomplished by means of the threaded adjustment member 102 and hand wheel 103. Screw 102 is threaded into the body 98 of the hanger. Guide cam 104 is fixed to the lower portion of the hanger 93 to control the position of the grinding motor and wheel during up and down motion of the lever 89. The cam 104 cooperates with a roller 105 mounted on the shackle 90 and has a vertical surface 106 and a horizontal surface 107. The surface 105 will determine the inward limit of movement of the grinder during grinding or lifting operation. It is to be noted that the grinder motor and wheel are horizontally offset from the pivot 91 so that they tend to swing inwardly against the work or the cam 104 as the case may be. In normal operation during traversing movement the grinding wheel would be in contact with the work. The amount of pressure applied against the work can be regulated by means of weights 108 mounted on rods 109 which are clamped on the pivot shafts 91 for movement with the shackle 90. Weights 108 may be moved along the rods 109 and held in positions of adjustment by set screw 110. As mentioned above the grinders are provided with traversing movement during grinding and while the turret is stationary and are then lifted and swung outwardly away from the work to permit free indexing of the turret.

The traversing movement is accomplished by relatively short rocking movement of lever 89 and lifting is accomplished by a movement of greater amplitude of the lever 89. As the lever moves upwardly beyond traversing position, roller 105 is brought into contact with the horizontal surface 107 of cam 104 causing the motor and grinder wheel to swing outwardly.

The levers 89 are caused to oscillate during traversing movement and to move upwardly beyond traversing position during indexing of the turret by means of push rods 111 which are connected to the outer ends of the levers 89. The rods 111 of the grinding stations and 8 have their lower ends connected to lever arms =112 mounted on a shaft 113 which is supported upon brackets 114 and extends across the base and through the sides of the base. The rods 111 at the grinding stations 6 and 7 are connected to levers 1 15 mounted on shaft 116, supported upon blocks 117 in the base parallel to shaft 113. Shaft 116 does not extend through the base walls, but levers 115 project through slots 118 in the base. (See Figures 8 and 9.)

Shafts

113 and 116 are connected for simultaneous movement by means of intermeshing

gear segments

119 and 120 carried by the respective shafts. Gear segment 119, in turn, meshes with a rack 121 fixed to a slide 122 that is moved by cam 65 through a follower roller 123 on the slide. Cam 65 is provided with a series of four rises 124 which, with the intermediate recesses 125,

provide four cycles of traversing movement of the grinder wheel during each dwell of the turret. Cam 65 has another rise 126, of greater amplitude than the rises 124, to lift the grinders out of grinding contact with the bits for indexing movement of the turret. The weight of the grinding mechanism will be sufficient to hold roller 123 in contact with cam 65.

It is extremely important that the bits be accurately placed in the bit holders if proper grinding is to be done. For this reason, a bit positioning arm 127 is provided at the loading station. Arm 127 is mounted upon a vertical shaft 128 for swinging movement to and from the loading position. The arm has a bit-receiving notch .129 into 6 which the end of a bit is seated and held until locked in the bit holder. The arm normally occupies its operative position adjacent a bit holder, as shown in Figure 3, but is swung in a clockwise direction out of the path of the bit holder during indexing movement of the turret. This is accomplished by mechanism shown in Figure 12. At its lower end, shaft 128 carries an arm 130 which is connected by a link 131 to one end of a hell crank 132. The bell crank is pivoted at 133, intermediate its ends, and its opposite end is positioned to be contacted, and moved, by a roller 134 mounted on the bull gear segment oscillating cam 64. Once each revolution, just prior to the start of the indexingmovement of the turret, roller 134 contacts bell crank 132 to cause the positioning arm 127 to move out of the path of the bit holder which is at the loading station. Just as soon as that bit holder has moved from the loading station, the arm 127 moves back to its operative position under influence of spring 135, which has one end connected to crank 132 and the other end to the underside of upper partition 13, to be ready for the next loading operation.

Although the operation of the machine has been described in connection with the construction of the various mechanisms, it will be briefly summarized. When the machine is started, arm 127 will be in position at the loading station. A bit will be inserted in the bit holder and locked in place while its end rests in the notch in arm 127. The arm, through contact of roller 134 with bell crank 132, will rock away from the bit holder and the turret will index one step, bringing the loaded bit holder to the first grinding station and the next bit holder to the loading station. Arm 127 will rock back to active position and a second bit will be positioned during the dwell of the turret between indexing steps. The first bit holder, at the first grinding station, will begin its oscillation, caused by movement of the bull gear segment and consequent oscillation of the track sections as described. This will cause the bit to be ground, in arcuate form with the center of the are on the axis of the shaft supporting the spur gear 66 beneath the loading station and the axis of the bit holder shaft 24. The bit holder will oscillate through two complete cycles. During this time, the grinder at the first station will complete four vertical traversing cycles under the influence of the camv 65. This will prevent localized wear of the grinding wheel. When the oscillating and traversing cycles are completed, the grinder lifts and swings outwardly and the turret again indexes. This brings the first bit to the second grinding station and the bit just loaded to the first grinding station. This operation is continued, step by step, until the bits are carried to each of the grinding stations and arrive at the unloading station. Here the sharpened bit is taken from the holder.

While in the above one practical embodiment of the invention has been disclosed, it will be understood that the particular structural details described and shown are merelyby way of illustration and the invention may take other forms within the scope of the appended claims.

' What is claimed is:

r1. A bit grinding machine comprising, a base, a turret rotatably mounted on said base, a plurality of bit holders rotatably mounted on said turret equally spaced therearound, means to rotate said turret step by step With an appreciable dwell between indexing steps to move said bit holders successively to positions constituting a loading station, at least one grinding station and an unloading station, grinding means at said grinding station for grinding contact with vertical surfaces of bits carried by said bit holders, and means operable in timed relation with respect to said turret rotating means to oscillate said bit holders horizontally at the grinding station during the dwell of said turret intermediate indexing steps.

2. In a bit grinding machine as claimed in claim 1, said means to oscillate said bit holders including guide arms connected to said bit holders, a guide track carried by said base to receive said guide arms, said track including a pivotally mounted section adjacent said grinding station to receive said guide arms when said bit holdersare at said grinding station, and means to oscillate said pivotally mounted track section.

3. In a bit grinding machine as claimed in claim 2, said means to oscillate said pivotally mounted .track section including a gear upon which said track section ismounted, a cam and cam follower, means interconnecting said cam follower and said gear, and means to rotate said earn.

4. In a bit grinding machine as claimed in claim 1, said means to oscillate said bit holders including guide arms connected to said bit holders, guide means carried by said base for engagement with said guide arms, said guide means including a section pivotally mounted with its pivotal axis in alignment with the. pivotal axis of a bit holder at said grinding station, the engagement of said guide arms with said guide means at said grinding section being with said pivotally mounted section at a point removed from said aligned axes, and means to oscillate said pivotally mounted section.

5. In a bit grinding machine as claimed in claim 4, said means to oscillate said pivotally mounted section including a gear upon which said section is mounted, a cam and cam follower, means interconnecting said cam follower and gear, and means to rotate said cam.

6. .A bit grinding machine comprising, a base, a turret rotatably mounted on said base, a plurality of bit holders carried by said turret equally spaced therearound, means to rotate said turret step by step with an appreciable dwell between indexing steps to move said bit holders succesisvely to positions constituting a loading station, at least one grinding station and an unloading station, grinding means at said grinding station for grinding contact with vertical surfaces of bits carried by said bit holders, and means timed with said turret rotating means to move said grinding means vertically to traverse bits at said grinding station during dwells of said turret and move and hold said grinding means away from said bit holders and out of contact with said bits during indexing steps of said turret.

7. In a bit grinding machine as claimed in claim 6, said grinding means comprising a grinding wheel and motor, a pivotal mounting for said grinding means positioned intermediate parallel vertical planes including respectively the center of gravity of said grinding means and the surface of the bit to be ground, whereby the weight of said grinding means will hold said grinding wheel against the surface of the bit to be ground.

8. A bit grinding machine comprising, a base, a superstructure above said base and carried thereby, a turret rotatably mounted on said base, a plurality of bit holders carried by said turret spaced equally therearound, means to rotate said turret step by step with appreciable dwells between each indexing stem to move said bit holders successively to positions constituting a loading station, at least one grinding station and an unloading station, a grinder at said grinding station including a vertically positioned motor and a grinding wheel carried thereby, a lever pivotally connected for vertical movement to said superstructure and said motor pivotally connected to said lever, said pivotal connection between said motor and said lever being intermediate two parallel vertical planes including respectively the center of gravity of the grinder and the surface to be ground of a bit in a bit holder at said grinding station, whereby the grinder will rock about its pivot by gravity to hold said grinding wheel against said bit surface, and means to rock said lever vertically to cause said grinding wheel to traverse the surface of 8. the bit to be ground during dwells of said turret and to move and hold said grinding wheel out of contact with said bit during indexing movement of said turret.

9. In a bit grinding machine as claimed in claim 8, said means to rock said lever including a cam and cam follower, and means interconnecting said cam follower and said lever.

10. In a bit grinding machine as claimed in claim 9, a stop on said superstructure for contact with said grinder when said grinder has been lifted a predetermined distance.

ll. In a bit grinding machine as claimed in claim 8, means adjacent said grinding station to oscillate said bit holders when at said station.

12. In a bit grinding machine as claimed in claim 8, said 'bit holders having guide arms connected thereto, a track carried by said base to receive said guide arms, said track including a pivotally mounted section adjacent said grinding station, and means to oscillate said pivotally mounted track section.

13. In a bit grinding machine as claimed in claim 12, said means to oscillate said pivotally mounted track section including a gear upon which said track section is mounted, a cam and cam follower, means interconnecting said cam follower and said gear, and means to rotate said cam.

14. In a bit grinding machine as claimed in claim 1, gage means at said loading station to accurately position a bit in a bit holder at that station.

15. In a bit grinding machine as claimed in claim 14, means to move said gage means out of the path of movement of said bit holders for indexing movement of said turret.

16. A bit grinding machine comprising, a base, a shaft journalled in said base, a turret journalled on said shaft, a motor to drive said shaft, an indexing cam fixed to said shaft, an articulated pawl journalled on said shaft, pins projecting from said turret spaced equally therearound and engageable in succession by said pawl, a cam follower on said pawl, a plurality of bit holders equal in number to said pins equally spaced around said turret, said cam being shaped to move said pawl into the path of said pins to advance said turret step by step with appreciable dwells between indexing steps to move said bit holders successively to positions constituting a loading station, at least one grinding station and an unloading station, and a grinder at said grinding station for grinding contact with a bit in a bit holder at that station.

17. In a bit grinding machine as claimed in claim 16, means adjacent said grinding station to oscillate said bit holders when at that station.

18. In a bit grinding machine as claimed in claim 16, means to cause said grinder to traverse said bits during dwells of said turret and move and hold said grinder out w of contact with said bits during indexing movement of References Cited in the file of this patent UNITED STATES PATENTS 766,403 Vincke Aug. 2, 1904 773,612 Wallace et al. Nov. 1, 1904 2,055,665 Moon Sept. 29, 1936 2,195,057 Wallace Mar. 26, 1940 2,579,337 Reaser et al Dec. 18, 1951