US1682672A

US1682672A - Grinding machine

Info

Publication number: US1682672A
Application number: US48734A
Authority: US
Inventors: Waldo J Guild
Original assignee: Heald Machine Co
Current assignee: Heald Machine Co
Priority date: 1925-08-07
Filing date: 1925-08-07
Publication date: 1928-08-28
Anticipated expiration: 1945-08-28
Also published as: FR1682672A; GB256582A

Description

5 Sheets-Sheet zu z'lc" W. J. GUILD GRINDING MACHINE Filed Aug. 7, 1925 Aug, 28, 1928.

Aug. 28, 1928.

W. J. GUILD GRINDING MACHINE Filed Aug. 7; 1925 5 Sheets-Sheet 2 Izamzor /ldo I uzld Aug. 28, 1928. 1,682,672

J. GUILD GRINDING MACHINE Filed Aug. '7, 1925 5 Sheesheet 3 I w @A w N ww, a, /%7/////////// J w ma Y @Y M. unw. RV

Aug. 28, 192s. 1,682,672

W. J. GUILD GRINDING MACHINE Filed Aug. '7, 1925 5 Sheets-Sheet 4 Aug. 28, 1928. 1,682,672

w. J. GUILD GRINDING MACHINE Filed Aug. 7, 1925 5 sheets-sheet 5 a M ,175' /f3 1 Jza i fig/M@ i as it approaches :finishe Patented Aug. 28, 1928.

UNITED STATES PATENT OFFICE.

wALDo .1. GUILD, OF woncns'rnn, MASSACHUSETTS, Assieno'a ro 'rrin HnALnirA'- CHINE coxrANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OF nAssA- i GRINDING MACHINE.

Application led August 7, 1925. SeriaLNe. 43,734.

The present invention relates togriiiding machines. In certain of .its aspects it isa plicable to any ofthe various types of grin ing machines, but its particular utility is'in 5 connection with internal grinding machines for grinding 4the internal cylindrical or conical surfaces of sleeves, gears, bushings,`

ball races and like articles.

The general Aobject of the invention'is to l0 provide a machine of this class that is capable of rapid and eilicient roduction of such ar- Y ticles, ground and nished 'uniformly' to within the closest limits of the desired and predetermined diameters. More specifically,"

15. the invention provides a machine which en tirely eliminates'the necessity for interruptions of the grinding by the o erator, which interruptions have heretofore een frequent, for the operator to plug or gauge the work Size. The machine is so organized that, in the grinding of each iece of work, there occurs, automatically rstly, the dressing or truing ofthe grindingr wheel, so that the final and finishing cuts which bring the Work to the desired size are always taken with a fresh cutting surface that is straight and true, for the production of a smooth truly cylindrical hole,-and Secondly, the automatic cessation lof grinding', I0 when the workpiece comes to size.

ln accomplishing these and other objects of the invention, certain of the mechanisms shown and described in the copending application of Heald, Guild, Burns and Garno,`

Serial No. 4,466, and to a certain extent those shown in the copendin'g application' of Kempton and Gallimore, Serial No. 6,689, are employed. In the machine of Said copending application, the automatic operations above 40 referred to are made responsive yto a workcalipering device, which ismaintained in coni. tact with the surface that is being ground; in the machine of the present invention however. the said automatic operations, namely the dressing or truing of the grinding Wheel,

followed by the resumption and then the subsequent cessation of the grinding, are obtained in response to predetermined movements of the cross-feed mechanism of the machine, i. e.,

5 the mechanism by which the Work and the grinding Wheel are progressively fed toward each other, ciosswise of the machine. In this way, the machine is enabled to handle workpieces 4having noncontinuous interior surtrating the cross-feed me chine. i Fig. 3 is a top plan view of the parts shown and the like,

faces, i. e., holes -with key-ways.

en using the which would not be possible w -WOrk-calipering device` above referred to.

eabove and other objects of the invention will appear from the following detailed description, taken in connection with the accompanyi'ng drawings, Ain which- Fig. 1 is'a front elevation illustrating an internal grinding machineto which my in vention is applied. i

Fig. 21s a front viewoii a larger scale, illusl1 n n chanism of said main Iig. 2.

lFig. 4 is a sectional view on the line44-4 oilig-3. i m

.Figs 5 and 6 are fragmentary sectional v iews, on an enlarged scale, taken, tively, onthe lines 5 5 and 6--6 o Fi 4.

Figf? isa view similar to Fig. 4, s owing respeca modification in the construction of the crossfeed mechanism.

Fig is a section on the line 8--8 of Fig. 7. Fig. 9 is a fragmentary sectional view on the line 9-9 of Fig. 7.

Fig.. 10 .is a wiring diagram of the elec trical parts and connections used in the Ineu chine.

parts in the different figures.

vides the usualreci riage 1 which ordinarily provided in any internal grinding machine.

in either case to movement between the grinding wheel and the work. As here shown. the table 1 su Like reference characters refer to like l .85 l

Referring first to Fig. 1, the machine prof:

procatory tablebr-carlieu i' ports and carries a wheel head 2, while t e work which isto be operated upon is held in a Work head 3, the latter being carried by a bridge 4, which spans the slideways provided by the machine frame for the back and forth movement ofthe table 1.

This back and forth movement of the table l to causethe rotating grinding wheel 5 to make the required interior traverse of the rotating workpiece 6 may be imparted in any Well known manner, as for instance, by the use of the fluid pressure controlling and reversing mechanism'which forms the subject jects matter of the copending application of Heald and Guild, Serial No. 629,882, tiled April 4, 1923, now Patent No. 1,582,468, granted April 27, 1926. Such mechanism, or its equivalent, forms no part of the present invention, and a detailed description thereof is therefore unnecessary; it is sufficient to note for the purposes of the present application, that the driving means employed for the reciprocation of the table 1, be it hydraulic drive, or

gear drive, or any other type, procures the reversal of said table at each end of the latters normal working stroke by the use of spaced

adjustable dogs

7 and 8, carried by the table 1 and adapted to alternately engage and move a reversing member 9; the latter, during the grinding operation, when the wheel 5 is moving back and forth within the workpiece 6, is situated between the two

dogs

7 and 8 in position to be struck alternately by said dogs, and by its consequent movement, first in one way and then the other, effects the reversals in the travel of table 1. In the machine herein illustrated, the grinding wheel 5 is rotated at high speed in any suitable manner,'as for instance, by a belt drive for the wheel spindle 10, the latter for this purpose carrying a pulley 10. The workpiece 6 is also rotated, but at a slower speeld, this rotation being imparted in any suitable manner as by a belt drive, not shown, from a countershaft.

The above described mechanism is all old and well known in the art and of itself forms no part of the present invention. 'libe latter involves the attainment, in connection with such or similar grinding machine instrumentalities, of the novel and useful oband results hereinbefore set forth, which are initiated by and under the control of the cross-feed mechanism of the machine,4

as disclosed in the form shown by Figs. 2 to 6 inclusive. or in the form shown by Figs. 7 to 9 inclusive. In the present machine. the cross-feed between work and grinding wheel is obtained by moving the wheel head 2 transversely of the reciprocatory table 1, but obviously, the invention is not limited in this respect, since the cross-feed mechanism, as hereinafter described, might as readily bc applied to the transverse movement of the work head 3.

The wheel head 2 of the machine is mounted on a cross-slide 11, the latter adapted to have an in and out movement on suitable ways 12 provided by a standard or bracket 13, Fig. 2, on the reciprocatory table 1. Movement of said cross-slide 11 is secured by rotation of a screw shaft 14, the latter enaagring an internally threaded member 15, Fig. 4, which is secured in any suitable way to the slide 11. The screw shaft 14 is journalled in a stationary sleeve 16, the latter being carried by a forward portion 17 of the bracket or standard 13. Any suitable means may be provided for preventing endwise movement of thescrew shaft 14, as for instance, ball thrust bearings 18, 18 cooperatingr with a shouldered portion 19 of said screw shaft. Rotation of said screw shaft, to procure the in or out movement of slide 11, is effected in the following manner In the form of cross-feed mechanism shown in Figs. 2-6 inclusive, and referring particularly to Fig. 4, a slecre 20 is suitably secured, by a key 21, or the like, to the outer end of screw shaft 14, and on this sleeve is rotatably mounted a member 22, hereinafter called a drive ring. Projecting inwardly from drive ring 22 is a stud 23, having journalled thereon the integrally united spur gears 24 and 25, the larger of which, 24, is in mesh with stationary spur gear teeth 26 formed on the sleeve 16, while the smaller of which, 25, is in mesh with spur gear teeth 27 formed on the sleeve 20. The drive ring 22 is subject to rotation, either by hand or automatically, as hereinafter described, and when such rotation is imparted, the gear 24, carried thereby aroundthe stationary `fear 26. is rotated on its own axis provided by the stud 23. This last named rotation, in which the gear 25 also participates, is transmitted by said last named gear, in mesh with the teeth 27, to the sleeve 20, thus to impart rotation to the screw sh aft 14, but at an angular speed very much reduced from that imparted to the drive ring 22.

The manual rotation ofthe drive ring 22 is effected b v a hand wheel 28. the latter. as shown in Fig. 4, being integrally connected by a plurality of ribs 29 with an annular hub 30, which is journalled and turns freely on the outer periphery of the drive rin,f r 22. Provision is made in the form of a screw 3l for temporarily locking the hub 30 and drive rin 22 for rotation in unison, and it will he un erstood that under these conditions, the clockwise rotation of hand wheel 28 will procure an inward feed of the grinding wheel 5 toward the surface being ground, while a eounterclockwise rotation of said hand wheel will procure a reverse movement of said grinding wheel, said movements in either case being effected by rotation of the screw shaft 14 as imparted by the reduction gearing above described between said screw shaft and the drive ring. In the ordinary operation of the machine however, the screw 31, as hereinafter described, is retracted from contact with the periphery of drive ring 22, leaving the hub 30 of hand wheel 28 free to rotate on said periphery, and other means are provided, as will now be described, for imparting the rotation of said hand wheel to said drive ring.

Immediately adjacent the inner face of hub 30 is disposed an annular member 32. hereinafter called the dial ring. this member buving secured thereto in any suitable manner,

lob

as by a pin 33, a ratchet ring 34, which finds journal bearin on an inward extension of the drive ring 22. Said ratchet ring 34 is the means by which the usual automatic inward feed of the grinding wheel 5, in response to the back and forth longitudinal traversing movements of said wheel, is imparted. To this end there is pivoted at 36 on the forward portion 17 of bracket 13 a member 37, Figs. 2 and 3, carrying a pawl 38 adapted to engage the teeth of ratchet ring 34, to rotate said ring and with it the dial ring 32, in a clockwise direction. A roller.

39 carried by member 37 is adapted, at the end of each left hand longitudinal stroke of the table 1, to engage a stationarycam 40, Fig. 1, which is carried by a suitable bracket 41 rising from the machine frame, said cam being longitudinally adjustable on said bracket so that it can be set to be engaged by the roller 39 at the proper time. When said roller 39 engages the cam 40, the mem ber 37 is rocked upwardly, thereby causing the pawl 38 to operatively engage and move the ratchet ring 34; in the operation of lthe machine, this produces a step-by-step clockwise rotation of said ratchet ring together with its attached dial ring 32, and this rotation is .communicated through the drive ring 22 to the screw shaft 14 in the following manner The dial ring 32, as shown in Figs. 4 and 5, carries a spring pressed'member 42, which acts as a paw] in cooperation with ratchetteeth 43 on the outer eriphcry of the dri-ve ring 22. Thus, througii this pawl and ratchet drive, any clockwise rotation imparted to the dial ring 32 is transmitted to the drive ring 22, and such clockwise rotation of the latter secures, through the reduction gearing above described, the rotation of the screw-shaft i4 in a direction to move the slide i1 inwardly, thus to feed the grindinfr wheel 5 toward the surface being ground. 'ldlc pawl and ratchet drive 42, 43 permits said dial ring 32 to be turned counterclockwise by said hand wheel, as hereinafter described, Without transmitting its rotation to the drive ring 22. Before describing in detail the use of said hand wheel 28 in connection with the res ective rings 22 and 32, the cooperation o the cross-fed mechanism with the various automatic'inn strumentalities of the machine will be fully set forth.

As shown in Figs. 3, 4 and 10, the dial ring 32 carries a cam projection ltf1-which, in the clockwise rotation of said dial rirg, is ada t ed to engage successively with two adjusta "le screws 45 and 49.. The. screw ll5 is carried by a pivoted ett?, and the rocking of said member 46, 'under the influence of said cam 44, causes the engagement two elec trical contacts 47 and d8, Fig. 10. The screw 49 is carried by a piyoted member 50, and the rocking of said member, under the influence of said cam 44, causes the engagement of two

electrical contacts

51 and 52, Fig. 10.

lthe contacts

51 and 52 causes longitudinal separation of the grinding wheel from the vworkpiece- 6, the former being moved to its rx'treme right hand position, as shown in When the terminals 4:7 andv4-8 make con? l tact, an electrical circuit is formed which, by the mechanism to be presently described, causes the table 1 to have an amplified stroke to the right, in order to withdraw the grinding wheel 5 from the work, and simultaneously causes a 'wheel dressing member or diamond 53 to move into the amplified path of said grinding wheel, thereby to true the periphery of the latter as it passes the point of said diamond. As shown by the wiring diagram of Fig. 10, electrical current may be supplied by a direct current generator 54 driven continuously by any suitable means, not shown, from the same source of power that is used for the rotation ot the grinding wheel or the work spindle. One terminal of 'this generator 54 is grounded, as shown at 55. and the other is connected by a supply lead 56 to the 4central bar or plate 57 ci a two-way switch,'the latter being designated as Aa whole by the numeral 58 and being disposed, as shown in Fig. 1, on the front of the machine. Said switch 58 provides additional contact plates or bars 59 and GO arranged on opposite sides oir the central bar 57 and adapted to be alternately connected electrically to said central bar 57 by a connector 61, which is mounted on an oscillatory member 62. The latter is pivoted at 63 and in its normal position, as shown in Fig. 110, disposes the connector (il in contact with and across the two plates 57 and 59; in the other position of movable member 62, the connector 61 connects the two plates 57 and 60.

rlthe normal. position of movable switch member 62 is that shown in Fier. 10, and under these conditions, the supply lead 56 from the generator 54 is connected to a iead Si taken off ot the plate or bar 59 of the switch 58. Said lead 64- runs to the coil of an electrolnagnet 65 disposed in the front of the machine, shown in Figs. 1 and 10. A return lead 66 from the coil of the electromagnet 65 is connected to a finger 6T provided on any convenient stationary portion of thc machine trame. A brush or plate 68 is carried by the table l, and during the normal working traverse of the table 1, when the grinding wheel 5 is moving back and forth within the workpiece, the finger 67 is in cor.- tact with the brush or plate G8. The latter is connected by u lend 63a to the Contact termi nal e8. lVhcn the terminals Il? and 48 are lill.)

brought together as above described, by the action of cam 44, the circuit through electromagnet is completed, since the terminal 47 is grounded` as shown at 47, Fig. 10. This energizes the electromagnet G5, causing attraction of an armature member 69, and the conse nent elevation of its attached lever arm 70, tliese parts being pivoted at 71 on the front of the machine. Such movement of the lever arm 70, responsive to the engagement of cam 44 with screw 45, is made use of to automatically interrupt the grinding operation on the workpiece 6 for the dressing and truing of the grinding wheel 5 in advance of the final and finishing cuts ta en by said wheel to bring the workpiece to the desired size. This involves the withdrawal of the grinding wheel 5 from theworkpiece, and the. dis osal,in the temporarily amplified path o movement of said wheel of the dressing device or diamond 53; these two operations are effected throiwh the medium of the lever arm in the following manmerz- As fully described in the copending application of Heald and Guild, Serial No. 25,900, filed April 25, 1925, the dressing device 53 may be moved into operative position through the medium of fluid under pressure, more especiallyl when such pressure fluid is employed for imparting reciprocation to the table 1. The means by which said pressure fluid is made available for the movement oi dressing device 53 into operative position forms, of itself, no part of the present invention, being fully described and claimed in the aforesaid application of Heald and Guild, Serial No. 25,900; it is suflicicnt to note, for pur oses of this application, that, as descri ed in said Heald and Guild application, the dresser point 53, suitably mounted on an adjustable screw plug 72, is lowered into operative position by the downward swinging movement of a carrying member 73, which turns on a trunnion 74 provided bypa suitable standard 75 rising from the stationary frame of the machine. `When the lever arm 70 is moved, a downward extension 76 thereof communicates said movement to a. valve 77, Fig. 1, thus making the pressure fluid active, through suitable connections, against a piston, not shown, which is operatively associated with the member 7 3, thereby to swing the dresser point 53 from the inoperative position, that it normally occupies, down into its operative position'in the path of grinding wheel 5. A handle 78 is also provided for this same purpose, for use when the member 73 is disconnected from the fluid pressure operating devices. My invention, of course, is not limited to the above described use of pressure fluid for disposing the dresser 53 in operative position; obviously, any other type of dresser moving mechanism, such as that disclosed in the copending application of Heald, Guild, Burns and Garno, Serial No. 4,466, filed January 24, 1925, mayn be made responsive to the ongagement of cam 44 with screw 45.

As before stated, the other operation inaugurated by said engagement is the automatic amplification of the reciprocatory path of table 1, to carry the wheel 5 past the dresser 53. As shown in Fig. 1, the left hand table dog 8, which limits the right handmovement of table 1, is carried by a block 79, which instead of being secured directly to the table l as in the case with the block 80 of dog 7, is mounted so as to be capable of sliding freely longitudinally of said table. Under normal conditions, when the table is making its usual working reciprocations to traverse the grinding wheel 5 back and forth within the workpiece, the block 79 of dog 8 is held in definite spaced relation to a block 81, which latter, the same as the block 8O oi right hand dog 7, is a stationary block adapted to maintain its'predetermined setting or adjustment longitudinally of the table 1, as given it by any suitable adjustment or holding devices, such for instance, as the hand screw nuts 82, 82 applied to both blocks 80 and 81 and engaging with the screw rack 83 on the table 1.

The device employed to hold the slidable block 79 in spaced relation to the fixed block 81 is here shown as a latch lever 84 pivoted at on block 81, and having its free end disposed by gravity in abutting relation to a shoulder 80 on block 79, thereby holding the block 79 at a predetermined distance to the right of block 81. When the latch member 84 is lifted to free its end from the shoulder 86, the normal connection between the slidable block 79 and the fixed block 81 is broken,

l and when this occurs on the right hand movement of table 1, the dog 8 will bear without effect against the member 9. Thus the right hand movement of the table 1 on this particular stroke will be extended beyond the usual reciprocatory working path, and the' grinding wheel 5 will be carried out of the hole in the workpiece to a point just beyond that occupied by the dressing device, which latter, as already described, has been moved into operative position as the amplified right h and travel of table 1 begins. This amplified right hand travel of table 1 involves relative sliding movement between said table and the block 79, owing to the obstruction which the reversing member 9 imposes against the dog 8 to prevent the block 79 from moving with the table; finally, the block 79 brings up agains*- the block 81` whereupon the solid backing thus afforded for the block 79 enables the dog 8 to shift the member 9. This procures reversal ofthe table 1, and the left hand movement of said table thus inaugurated is caused to restore the parts automatically to normal pos1tion in the following manner:

DIS

surfaces 88 and 89 for cooperation, respec` tively, with

inclined surfaces

90 and 91 at the lower corners of the block 79. A spring 924 presses said member 87 upwardly. In the normal grinding operation of the machine when the blocks 79 and 81 are connected by latch 84, the surfaces 88 and 89, although in the path of block 79, offer no effective obstruction to the back and forth travel of said block in unison with the table l, it being obvious that when either lower corner of the block under these conditions strikes either of the bevelled surfaces 90 or 91, such contact will wedge the spring 92 downwardly, said spring yielding silliciently to allow the block 79 to pass over the member 74. However,

when the block 7 9 has been freed from the 79 still free, finds the surface 88 in osition to Contact with the corner 90 of sai block, and under these conditions, the obstruction offered is sufficient to overcome whatever friction there may be tending to cause the block 79 to move to the left withy the table. The block 7 9 being thus-held stationary while the table 1 and block 81 continue to move to the left, the latch member 84 inall resumes its normal position relative to the lock .79, the end of said latch member dropping behind the shoulder 86 and the parts being thus automatically restored to normal position at the conclusion of each single amplified reciprocation of the table 1.

- Said single amplified reciprocation of th table 1 for wheel dressing purposes is, in the present invention, inaugurated automatically upon a predetermined preliminary amount of grinding having been done on each workpiece, throu h the

terminals

1,7 and 48 as already descri ed, thus moving the lever about its pivot 71. The lever 70 has a roller 98 on the upper portion thereof, and upon movement of this lever during normal working traverse of the grinding wheel 5, the roller 93 engages and lifts the latch lever 84, thus causing the above described amplified movement of the table 1, which carries the grinding wheel 5 to the right, past the diamond 53, and then to the left, again passing said diamond before resuming the normal reciprocatory traverse of the workpiece 6. Thereupon, by any suitable means, such as that shown and described in the aforesaid copending application of Heald and Guild, the diamond 53 is rocked upwardly into the inoperative position that it normall occupies.

On this amplified right han dressing stroke of the table 1, an arm 94, Fig. 1, piv

oted at and hanging by gravity in the position shown in Fig. 1, strikes an arm 95,

by the making of electrical contacts Fig.. 10, of movable switch member 62, thereby rocking said switch member away from bar 59, which prevents a repetition o the dressing stroke. Thereupon the connector 61 is disposed in position to connect the switch plates or bars 57 and 60. A lead 96 runs from the switch bar 60 to the coil of a second electromagnet- 97, and the other end of said coil 1s connected by a lead 98 to a linger 99 carried by the machine frame preferably adjacent to the linger 67. Said finger 99 makes contact witha brush or plate 100, carried by the table 1 ad] acent to the plate 68, and a lead 101 connects the plate 100 with the contact 52.

After the wheel dressing operation above described, and with the resumption of grind-- ing upon the workpiece 6, the inward feedmg of the grinding wheel 5 involves further clockwise rotation of the dial ring 62, which ultimately carries the cam 114. into engagement with the screw 49. The parts are so set and adjusted, as hereinafter described, that this engagement takes place just as the workpiece 6 reaches the exact desired size; the consequent rocking of member 50 brings together the

contacts

51 and 52 and completes the electrical circuit through the magnet 97, since the Contact 51 is grounded, the same as the Contact 47, at 473. Thus the electromagnet 97 is energized, causing attraction of an armature member 102 pivoted, as shown in Fig. 1, on the same spindle 71 which forms the pivot for the armature member 69. The armature member 102A provides a lever a-rm 103 for cooperation with the left hand. table dog 8 in the following manner Said table dog 8, as shown in Fig. 1, is pivoted at 104 to its carrying block 79, and normally rests by gravity against a pin 105, thereby to maintain its free end in position to engage and move the reversing member 9 at the end of the right hand normal working stroke of the table 1. When the magnet 97, in response to the grinding of the workpiece to the exact desired size, is energized, the lever arm 103 is raised into the path of dog 8, and the latter, on the right hand movement of table l, by reason of its pivotal mount-` ing, is free to ride on the upper surface of said lever arm; thus the striking end of said dog 8 is carried clear of the reversing member 9, and the table 1 continues its movement to the right, carrying the grinding wheel 5 out ofthe workpiece and well past the then inoperative dressing device 53, said table ultimately carrying the grinding wheel 5 into the position illustrated in Fig. 1, and there being brought to a full stop by any suitable means, such for example, as those shown in the aforesaid co ending application ofHeald and Guild, Seria No. 629,882. Thus with the coming to size of a given workpiece 6, the mechanism automatically secures the complete cessation of the grinding operation, and the full longitudinal separation of the grinding wheel from the workpiece, permitting full access to said workpiece for its removal from the machine, and the insertion in said machine of a new unground workpiece while the grinding wheel 5 is entirely out o f the way.

The return to working position, from the full withdrawal position shown in Fig. 1, is effected by the s ifting of a hand lever 106, operatively connected to the reversing member 9 and adapted to throw said reversing member to the right, thereby to inaugurate a left hand movement of the table 1. On this left hand movement, an arm 107, pivoted at 85 and hanging by gravity in the position shown in Fig. 1, strikes an arm 108 of movable switch member 62, thereby rocking said switch member s0 that its connector 61 is returned to the position shown in Fig. 10, in readiness for the energization, at the proper time in the grinding of thenext workpiece, of the electromagnet which inaugurates, as above described, the wheel dressing operation. As shown in Fig. 1, and as described in the aforesaid copendin vapplication of Heald, Guild, Burns and arno, the

arms

95 and 108 of movable switch member 62 are offset from one another, as are also the corresponding striking arms 94 and 107, respectively, of the table 1. As the table travels to the left to resume a working position, the dog 8, upon engagement with the member 9, yields upwardly and then, after assing over said member 9, drops by gravity into its usual position, so that said member 9 thereafter is disposed between the striking faces of the

dogs

7 and 8.

The quantity production of identical workpieces all ground to the same exact internal size, involves a predetermined setting of the cross-feed mechanism above described, by the aid of a sample workpiece or pattern, which is first ground to exact size in any suitable way, as by the use of ordinary sizing plugs or gau es. In the production of this sam le wor piece, the various electrical and ot ier automatic deviceshereinbefore referred to, are not em lo ed, and the cross-feed of the 'ndinv w ee is preferably effected by hand, t e hand wheel 28 for this purpose being secured` by screw 31, to the drive ringh22, Fig. 4. When the sample workpiece as been round to the exact desired size, the crosseed of the wheel 5 is diontinued, and the table l is then actuated to withdraw the grinding wheel from the workpiece and to dispose said wheel substantially in the dressing osition; this may be done by lifting the atch lever 84 manually and by shutting ofi' the supply of pressure fluid to stop the movement of the tab e when the latter reaches the desired position. Thereupon, the cross slide 11 being then in the precise position which secures the grinding of said workpiece to the desired inter* i! rliameter, the parts, without disturbing the position of said cross slide, are set so that the cam 44 ou the dial ring 32 will just bring the

contacts

51 and 52 together, this position signifying the cessation of the grinding operation by energization of the magnet 97, as above described. This setting of the dial rinef 32 is accomplished by manually turning the dial ring coiinterclockwise, an action which is permitted to take place without any turning of the drive ring 22, since the awl and ratchet drive 42, 43 between sai rings only works in a clockwise direction. In this position of engagement between cam 44 and screw 49, which causes the

contacts

51 and 52 to come together, a mark or pointer 109, Fig. 3, on a member 110, carried by bracket extension 17, always re iS- ters with a zero marking 111 of the 'al ring 32.

The next step in the setting of the parte is to turn the dial ring 32, through the hand wheel 28, backward or counterclockwise from this zero position through a selected number of dial ring indications, which may conveniently represent thousandths of an inch, thc number of such graduations representing the distance by which the operator desires the automatic wheel dressin operation to precede the attainment of nished size by the workpiece; in this position of the dial ring, the screw 45 is adjusted so that its engagement by cam 44 will just bring the contacts 47 and '48 together. The backward setting of the dial ring 32 to this point, which signifies theiniiuguration of the wheel dressing operation, by energization of the electromagnet 65, should be accompanied by acorrespondingmovement Y of retraction of the cross slide 11, and this in turn involves a counterclockwise rotation of the drive ring 22 in unison with the dial ring 32. To secure this operation, the mechanism provides a pawl and ratchet drive between the ub 30 of hand wheel 28 and the adjacent face of dial ring 32, consisting of ratchet teeth 112 formed on the face of said dial ring, for col operation with a spring pressed member 113 contained in a recess of said hub 30, as shown in Fig. 6 and adapted to operatively engage said teeth 112 when the hand wheel 28 is rotated counterclockwise. Therefore, when the screw 31 is tightened, to unite the hand wheel 28 and the drive rin 22 for rotation in unison, the counterclockwise rotation of said hand wheel, to set the cam 44 back to screw 45, is accompanied by a corresponding angular movement of drive ring 22, which retracts the cross slide 11 a slight distance, thus to dispose the periphery of the grinding wheel at the point selected for the inauguration of the ressing operation of said wheel.

With the grinding wheel 5 in the position above described, the dressing mechanism is adjusted so that the diamond point 53` when rocked down into operative position by the handle 78, will barely make contact with the l periphery of said grinding wheel this is donetent,-in other words, at each retraction, the

by adjusting the standard 75, or by adjusting screw 72, as required,-and then the parts of,

the dresser mechanism are fixed in this position and require no further adjustment. It will thus be seen that in the grinding -of a subsequent workpiece, the above described setting of cam 44 with relation to sc rew 45 will cause the grinding operation to be interrupted when the contacts 47 and 48 are brought together, the grinding wheel 5 being then subected automatically to the dressing operation heretofore described, following which the grinding operation is automatically resumed to bring the work to the desired finished size.

The settings of the cross-feed and contact mechanisms above described are adapted. for the production, by the machine, of any desired number of pieces, corresponding to the sainple workpiece and ground internally to the same diameter,it being iuiderstood, of course, that with each successive workpiece introduced to the machine, the grinding wheel 5 is fed inwardly automatically by the pawl and ratchet

drive

38, 34 for the dial ring 32, whose clockwise rotation is in turn imparted to the drive ring 22 by the pawl and ratchet drive 42, 43.

At theV finish of the grinding operation on each workpiece, it is necessarv, of course, to retract the cross slide 11 by hand, in order that the grinding wheel 5 may be in position to enter the unground hole in the next workpiece, without striking the edge of said hole.

` lt will readily be seen that if the counterclockwise rotation of drive ring 22 required for this retraction is accompanied by a similar rotation of cam 44, no greater in angular eX- tent, then said cam, in the grinding of the new workpiece, will cause the contacts 47 and 48 to come together prematurely, inasmuch as the grinding wheel 5, having been reduced in diameter by the dressing operation taking place during the` grinding ot the preceding workpiece, as well as by inevitable wear thereon in the grinding done by it since said dressing, will not make contact periplierally with the dresser point 53. In like manner also, under the conditions assumed, the bringing together of

contacts

51 and 52 will also be premature, in consequence of which the automatic cessation of the grinding oieration, brought about by the energization oi electroniagnet 97, will take place before the hole in the workpiece has been ground to the required diameter.

n Therefore, in order to compensate for wear on the grinding wheel and also for the reduction of its diameter by dressing, means are provided whereby, at each retraction of the cross slide 11, the countei'clockwisc turnd ing of the drive ring 22 to accomplish said retraction. is accompanied by a counterclockwise turning ot the dial ring 32 and cam 44 which is invariably of greater angular ex cam 44 is set back with reference to the drive ring 22, in the following manner r-l-As shown in Figs. 2, 3 and 4, the hand wheel 28, whose counterclockwise rotation is employed to produce the above described retractions of lcross slide 11, carries in any suitable manner, as by means of screws 114 a block 115, the purpose of which is to adj ustably support a transverse pin 116, whose ends project beyond said block. The pin 116 is threaded, and its adjustment endwise in the block is secured in any suitable manner, as by a knurled nut 117 in threaded engagement with said pin and disposed in a recess of said block. The drive ring 22 provides a pair of lugs 118 and 119,

on opposite sides of the block 115 of the hand wheel 28, these lugs being spaced apart. peripherally to provide lost motion between hand wheel 28 and drive ring 22. By clockwise rotation of the hand wheel 28 relative to drive ring 22, the right hand end of pin 116 will be brought into engagement with the luer 119, and by counterclockwise rotation of sai handwheel, relative to drive ring 22, the left hand side of block 115 will be brought into contact with lug 118.

.During the automatic inward feed of cross slide 11, accomplished, as above described, by clockwise rotation in unison of drive rin 22.and dial ring turns clockwise7 because one of the ratchet teeth 112 of dial ring 32 will press operatively against the pawl 113, thereby. causing the h and wheel 28 to move in unison with the dial ring 32. At the finish ofthe rinding operation on :i given workpiece, with the parts in the positions illustrated in Fig. 1, let it be assumed that the hand wheel 28 is in the position illustrated in Fig. l, where the right hand end of pin 116 bears against lug 119 l of drive ring 22. For the necessary retraction of cross slide 11, before the table 1 is moved to the left to carry the grinding wheel into the new unground work iece, the hand wheel 28 is turned countercloc wise; the dial ring 32 participates in this counterclockwise rotation from its very commencement, owing to the pawl and ratchet drive 113, 112 above described, but the drive ring 22 does not begin to move counterclockwise until the hand wheel 28 has been turned fai' enough to carr the left hand side of block 115 against the lug 118 of said drive ring. In this way the cam 44 carried by the dial ring 32 is, at each retraction of the cross slide 11, turned back a definite amount in excess of the turning back of drive ring 22, this amount being the distance showin on Fig. 1 between the" lug 118 and the side of block 115, and this dis-v tance being adjustable my manipulation of the knurled nut 117 to vary the right hand projection of pin 116 beyond said block, thereby to space said block more or less from the lug 119. The nut 117 should be adjust/ed 32, the hand wheel 28 also so that the cam 44 and the dial ring 32 will, at each such retraction of the cross Slide, be turned back in excess ot' the retraction of the drive ring 22, by an amount which is greater than the largest estimated possible wear of the grinding wheel, because it is this excess retraction which causes the axis of the grinding wheel to be moved ever ncarcr to the dressing plane at each successive dressing operation, in order that contact between the wheel and dressing device may be assured. It will be understod that the operator, after retracting the cross slide 11 sutliciently by countercltckwise rotation of hand wheel 28, will then be required to turn said hand wheel clockwise through a small arc to bring the right hand end ot pin 116 into contact once more with lug 119; this clockwise rcadJustment of the hand wheel 28 takes place without any corresponding movement ofthe other parts ot the cross-feed mechanism, inasmuch as said hand wheel 28 is free to turn clockwise on the drive ring 22: any tendency of the drive ring 22 or dial ring 32 to follow the hand wheel 28'at this time may be overcome, if necessary, by imposition of a suitable friction or drag exerted against the drive ring, as indicated by the spring friction plug 120, Fig. 4.

From the foregoing it will be clear that with an accurate setting ot the parts, as determined by the sample workpiece used as a pattern, t ie mechanism, operating as above described, will produce any desired number ot similar workpieccs, all ground internally to exactly the same diameter as the sample. This result follows from the fact that, during' the linal stages of grinding on each workpiece, a fixed and invariable advance of the cross slide occurs, from the time of engagement ot the contacts 47 and L18 until thetime of engagement ot' the

contacts

51 and 52; inasinuchas the engagement of the contacts 47 and L18 always secures tangency between the periphery of grinding wheel 5 and a tiXed vertical plane, irrespective of wear or other variable influences on said wheel, it is clear that the ensuing limited advance of the periphery ot the wheel beyond said plane, being always in every case through the same distance. will result, in substantially absolute uniformity of' product. It will be readily understood that the machine parts should be srt so that the aforesaid fixed and invariable advance of the cross slide from the dressing operation to the cessation ofthe grinding operation, will be greater than the amount by which the grinding wheel is reduced by dressing. 1f this were not so, the grinding wheel would have cut the workpiece beyond the desired tinished Surface prior to the engagement of the contacts 47. and 48. Such reduction of the. wheel by dressing will be necessarily equal to the ditterence between the estimated wear of the wheel, as signiied by the setting of the knurled nut 117, hereinbe fore described, and the actual weer of the grinding wheel, which can only be determined by experiment. In practice, however, the operator of the machine will set the parts so that this fixed advance subsequent to dressing will be greater by a safe margin than the reduction or' the wheel by dressing, which can be estimated. as indicated. Such adjustment, of course, is etccted by turning ot' the set screws 45 and 49.

In the modified form of the cross-feed mechanism shown in Figs. 7,8 and 9, the principle of operation is the same as above set forth, but a variation in construction, tending toward simplification, is employed. As shown in Fig. 7, a single annular member 121 combines the functions of the drive ring and the hand wheel of the previously describen construction, said member having a hub por-A tion 122, journalled on the sleeve 2l) which is keyed to screw shaft 14, and said member providing the stud 23 for the support of the

reduction gearing

24, 25 employed for the drive of said sleeve 2O through gear 27. Directly secured to the annular member 121 is a ratchet wheel 34 and the usual pawl 38, actuated as above escribcd by the reciprocations of table 1, cooperates with said ratchet wheel to produce step-by-step clockwise rotation of member 121 for the progres sive inward feed of cross slide 11.

The cam 44 in this construction is carried by a dial ring 32, the latter, as shown in Fig. 7, being rotatably mounted upon and supported by the annular member 121. As best shown in Fig. 9, the dial ring 32 on its opposite sides or faces is provided with ratchet teeth 112, 126, the former for cooperation with a spring pressed pawl 113 carried by the annular member 121. and the latter for cooperation with a spring pressed pawl 123 carried by another ring member 129. Said ring 129, like the dial ring 32, is mounted upon the annular member 121, and said ring 129 is frictionally constrained from rotation by the drag imposed by a pair of stationary spring pressed pads or

shoes

130, 130, Fig. 8.

This mechanism is adapted to be adjusted and set in substantially the same manner as heretofore described for the successive en gagements ot cam 4-1 with screws 45 and 49, 10, whereby automatic dressing of the grinding wheel 4and subsequent automatic cessation of the grinding operation are secured. The clockwise rotation of member 121 for the inward feed of cross slide 11 is imparted to the ring 129 by a post 131, Fig. 8, projecting from member 121 and received in an elongated slot 132 of ring 129; adjustable screws 133 and 134, at the ends of said slet, are adapted to be engaged by post 131, depending upon the direction of rotation of the member 121. At the end of cach grinding operation, the manner in which the cam 44 is set back, on the retraction of cross slide 11, a predetermined distance in excess of the backward feed of'the other parts, is as tollows z- The member 121 is turned backwz-ird by hand to retract the cross slide, and this counterclockwise movement is imparted to the dial ringr 32 by the pawl and ratchet drive 113, 112, the parts, except ring 129, which lags until post 131 picks up screw 1 3-1, moving backward in unison. Then, in the grinding of the next workpiece, the member 121 is given clockwise rotation, either by hand or by the pawl and ratchet drive 38, 34a. However, at the commencement of this clockwise rotation, the dial ring 32, carrying cam 44: will lag. because the'pawl 128 carried b v the normally stationary ring 129 will, by its engagement with one of the ratchet teeth 126, prevent clockwise rotation of the dial ring 32a. stationary, notwithstanding the inward feed of the cross slide until the member 121 has travelled far enough to carry the post 131 into contact with the screw 133 of ring 129: there after, the ring 129 is obliged to rotate in unison with the member 121,4 and this permits the dial ring 32 and cam 44 to partake of similar clockwise movement.

In the first described form of the invention, compensation for reduction in diameter. bv

` wear and dressing of the grinding wheel 5 is obtained, between operations on successive worlrpieces. in the act of retraction the cross slide 11 by the hand wheel. this imparting to the cam 44a backward setting in eiccess of that imparted to the feed ratchet 34. In the second form of the invention, the same result is obtained, for 'the same purpose, between `grinding' operations on successive workpieces. when the hand wheel is turned back to retract the cross slide 11. but in this instance the cam 44 is turned back the same distance as the feed ratchet: however. the cam 44 is not picked un on the ensuing` inward feed of the cross slide until said inward feed has progressed a predetermined amount. It will also he noted` in this second form of the invention. that the operator is not required, after turningl the hand wheel countercloc wise to retract the cross slide 11. to make any subseonent clockwise adiustment or settiner of said hand wheel. as is the case with the first described form of the invention.

In both forms of the invention. the automatic wheel dressing operation takes place in advance ot the final and tinishinrr cuts which bring the workpiece to the desired Finished size. and this interruption of the grinding operation on each workpiece. for lthe purpose of dressinY the wheel. relieves the sidewise pressure ci the wheel against the workpiece which has been buiit up in the grindy ing operation by successive advances of the cross-feed screw 14, and which pressure tends Thel ring 32 and cam 44 will be. held' sometimes to spring the wheei spindle 1t), and toe cause uneven wheei wear. lit-Then' the grinding wheel, following its dressing, reenters thworkpiece, the cross-feed imparted to it .for taking the final and finishing cuts to bring the work to size, is not suiiicient to build up any .objectionable or excessive pressure, and hence these final and finishing cuts are taken under ideal grinding conditions. The automatic cessation of grinding, in both forms of the invention, is brought about, as herembefore described, by a predetermined advance oi the cross-slide 11 beyond the position which it occupies when the wheel dresslng operation occurs; as previously described, said dressing position oi the cross-slide is advanced successively for each new workpiece.

I claim:

I 1. The combination with a grinding mai chine comprising means for supporting the work, means for supporting a grinding wheel, means for producing a reciprocating motion of one ot' said before-mentioned means with relation to the other, means to so control said motion as to cause a relative traversing motion between the wheel and the work, one past the other in contact, or to cause withdrawal of one from contact with the other and subsequent restoration to contact, a tool for dressing the grinding wheel so mounted that it is engaged b the said wheel when the contact between t e work and grinding wheel has been so interrupted, and feeding mechanism that causes the grinding wheel and work to move one relative to the other transverse to said traversing motion to maintain grinding contact; of devices operated directly by said feeding mechanism and operable on said motion-controlling means to cause the withdrawal motion and then to restore the contacting traversing relation of work and grinding wheel, whereby the grinding may proceed by a succession of uninterrupted traversing motion confined to the surface to be ground, and at a stage determined directly by the movement of the feeding mechanism, the contact of rinding wheel and work is automatically interrupted, the grinding wheel is dressed and traversing contact with the work is resumed.

2. The combination with a grinding machine comprising means for supporting the work, means for supporting a grinding wheel, means for producing a reciprocating motion of one of said before-mentioned means with relation to the othenmeans to so control said motion as to cause a relative traversing motion between the wheel and the work, one past the other in contact, or to cause withdrawal ofone from contact with the other and subsequent restoration to contact, a tool for dressing the rinding wheel so mounted that it is engagedy the .said wheel when the contact between the work and grinding wheel has been so interrupted, and feeding mechat move one relative to the other transverse to said traversin motion to maintaln grindin contact; of evices operated directly by said feeding mechanism and operable on said motion-controlling means to cause the withdrawal motion and then to restore the contacting traversing relation of Work and grinding wheel, and means for automatically operating the feeding means during the traversing contact of the Work and grindingwheel before and after the withdrawal motion, whereby the grinding may proceed by a succession of uninterrupted traversing inotions confined to the surface to be ground, and at a stage determined directly by the movement of the feeding mechanism, the contact of grinding Wheel and work is automatically interrupted, the grinding wheel is dressed and traversing contact with the work is resumed.

3. In a grinding machine, a grinding wheel, mechanism for procuring a cross-feed between said wheel and a workpiece, means responsive to successive feeding movements of said cross-feed mechanism for procuring cessation of grinding on successive workpieces. as the latter reach a. predetermined size, and means responsive to the retractile movements of said cross-feed mechanism. between successive grinding operations, for compensating for the Wear of said grinding wheel.

4. In a grinding machine, a grinding wheel. mechanism for procuring a cross-feed between said wheel and a workpiece, means responsive to successive feeding movements of said cross-feed mechanism for procuring a dressing operation on said grinding wheel during the grinding of each successive workpiece, and means responsive to the retractile movements of said cross-feed mechanism. between successive grinding operations, for compensating for the successive reductions in diameter 0f said Wheel by said dressing operations.

5. In a. grinding machine, a grinding wheel, mechanism for procuring a cross-feed between said Wheel and a workpiece. means responsive to successive feeding movements of said cross-feed mechanism, in the `grinding of successive Workpieces, for dressing said wheel and for procuring cessation of each successive grinding operation when the workpiece reaches a predetermined size, and means responsive to the rctractile movement of said cross-feed mechanism` between successive grinding operations. for compensating for the reduction in diameter of said grinding wheel, both by said dressing and by wear during grinding.

6. In a grinding machine, a grinding wheel, mechanism for procuringa cross-feed between said wheel and a workpiece, means directly actuated and controlled bv said crossfeed mechanism in the grinding of each workpiece, and set in operation only after said cross-feed mechanism has caused preliminary grinding of a given workpiece, to procure a dressing operation on said grinding wheel, and means for automatically procuring cessation ofthe grinding operation on each workpiece upon the feeding movement of said cross-feed mechanism through a. redetermined distance beyond the point wiiere said dressing occurred.

7. In a cross-feed mechanism of the class described, a cross-slide, a driving member therefor, means for progressively and automatically advancing said member, a second member adapted to advance with said driving member, means operable by said second member for securing cessation of feeding movement of said cross-slide` and means automatically operated by the cross-slide operating mechanism in retracting the cross-slide for setting back said second member a predetermined distance in excess of said driving member.

8. In a grinding machine, a grinding wheel,

mechanism for procuring a cross-feed bc' tween said wheel and the workpiece. said mechanism comprising a cross-slide, a driving member therefor, means for progressively and automatically advancing said member. a second member adapted to advance with said driving member, means operable by said second member for securing cessation of the grinding operation by said wheel, and means automatically operated by the cross-slide operating mechanism in retracting the crossslide, following said cessation. for setting back said second member a predetermined distance in excess of said driving member.Y

9. In a grinding machine, a grinding wheel` a wheel dressing device. mechanism for procuring a cross-feed between said wheel and the workpiece, a cross-slide forming part of sa id las!V named mechanism. a driving member for said criiss-slide. means for progressively and automatically advancing said member. a second iiiemher adapted to advance with said driving member. means responsive to advancement of said second member for securin; r successively the operation of said dressing device and the cessation of grinding on the workpiece, and means automatically operated by thc cross-slide operating mechanism in retracting the cross-slide. following said cessation. for setting back said second member a prcdcwriiiined distance in excess of said driving member.

l0. In a cross-feed mechanism of the class described, a cross-slide. an actuating niembci therefor. mains for progressively and autoniaticallv advancing said member, a secon'l member adapted to advance with said :ictuating member. nir-ans operable by said second member for procuringr cessation of the .feeding movement of said cross-slide, a hand wheel operatively associated with said actuwheel, mechanism for procuring a cross feet between said wheel and the workpiece, said mechanism comprising a cross-slide, an actuu ating member therefor, means for progressivelv and automatically advancing said member, a second member adapted to advance with said driving member, means oper able by said second member for procuring cessation of grinding on said workpiece, a hand wheel operatively associated with said actuating member and said second member, and means automatically operated on the retraction of said cross-slide by said hand wheel, following said cessation of grinding, for producing,r an angular displacement between said actuating member and said second y member.

12. In a cross-feed mechanism of the class described, a cross-slide, an actuating member therefor, means `for progressively and automatically advancing said member, a second member adaptedto advance with said driving member, means operable by the advance of said second member Jfor procuring cessation of the feeding movement of said crossslide, and a hand wheel operatively associatedwith said actuating member and said second member and'adapted when operated for the retraction of said crossslide to secure a predetermined angular displacement between said two members, there being a lost motion connection between said hand wheel and said actuating member. v

13. In a cross-feed mechanism of the class described, a crossslide, a memberrotatable in opposite directions to secure, respectively, the feeding and withdrawal movements of said cross-slide, a second member rotating with said first member when the cross-slide is fed, devices directly set in operation by said second member on its arrival at a predetermined point adapted to procurecessation of said feeding movement, and means operable on the reverse rotation of said members, to withdraw said cross-slide, and automatically procure a predetermined angular displacement between them.

14. In a grinding machine, a grinding wheel, a mechanism for procuring a crossfeed between said wheel and the workpiecef mechanism comprising a cross-slide, ier rotate.l opposite directions 'to procure. rester be 'feeding and withdrawal mo 'd cross-slide, a second member aid first member when said cro '1 ted, devices directly set operati id .reward member on its arrival. at a mi.ed point adapted to procure cessation of the grinding opera.- tion on said workpiece, and means operable on the reverse rotation of said members, following said cessation, to withdraw said crossslide, and automatically procure a predetermined angular displacement between said members.

l5. In a cross-feed mechanism of the class described, a rotatable actuating member, two other rotatable members operatively asso ciated with said actuating member, friction means for restraining rotation of one of said members, a pawl and ratchet drive for the other of said members both from said actuating member and said frictionally re# strained member, and means for moving said irictionally restrained member from said actuating member, after a predetermined lost motion between them, whereby to automatically change the relationship of said other member with respect to said actuating inember, responsive to each double motion, clockwise and counterclockwise, ci said actuating member.

1. In cross-feed mechanism of the class described. a feed screw, an actuating member for said feed screw, a pair of contact making devices, an element normally progressivelv advanced by said actuating member and adapted to successively act-nate said contact making devices, and means responsive to withdrawal movements of said feed screw `for changing the rotativeA relation of said element to said screw by a. predetermined amount.

l?. In mechanism of the class described, a feed screw, a driving element adapted when moved to turn said feed screw, a. pair of contact making devices, a ring normally carried by said driving element and adapted to actuate said Contact making devices, a hand wheel to withdraw said feed screw, and means, re

sponsive to a withdrawal of said feed screw by said hand wheel to a given position of said feed screw, for changing the relative positions of said ring and said contact devices.

18. In mechanism of the class described, a feed screw, a driving element adapted when moved to turn said feed screw, a pair of contact making devices, a ring normally carried by said driving element and adapted to actuate said Contact making devices, a hand wheel to withdraw said feed screw, and means, responsive to a withdrawal of said feed screw by said hand wheel to a. given position of said :feed screw, for changing the relative positions of said ring and said contact devices by' a predetermined amount.

i9. In mechanism or the class described, a teed screw, a driving element adapted when moved to turn said feed screw, a pair of contact making devices, a ring normally carried by said driving element and adapted to aetuate said contact making devices, a hand wheel to withdraw said feed screw, and means, responsive to a withdrawal of said iso feed screw by said hand wheel to a given position of said feed screw, for changing the relative positions of said ring and said coniact devices by a predetermined adjustable amount.

20. In a grinding machine, a grinding wheel, a feeding element which, when moved, causes said grinding wheel and a workpiece to approach or recede, a dressing device, means for moving said grinding wheel and dressing device, one relative to the other, iii a line parallel to a geometrical element of the surface of said wheel, while maintaining the dressing device a fixed distance from the line. of contact of said wheel and workpiece as hereinafter defined, thus to remove material from said grinding wheel, automatic means to move said feeding element, measuring means associated with said automatic fecdl ing means to measure increments of said feed.` the means for moving said grinding wheel and dressing device relatively being setin operation by said measuring means, whereby it may be caused to operate after preliminary grinding and at a point in the movement of said element which is advanced by a constant increment for successive grinding operations, means to cause the automatic feeding means to cease moving said element, said means being also actuated by said measuring means, said measuring means and the means to cause the automatic feeding means to cease operation being thus adapted to measure off a fixed movement of said element after causing said dressing operation, the aforesaid line of contact of said wheel and workpiece being defined at the moment said feeding means has last moved said element.

21. In the art of grinding a plurality of Workpieces to the same size in a given dimension, the improvement which consists in determining approximately the amount of wear of a grinding wheel durin each grinding operation, causing a grinding wheel to be advanced into contact with successive work pieces (and thereby cutting said workpieces) by an increasing amount for each successive workpiece, the increase being a constant one and being greater than the largest estimated possible wear of the grinding wheel, at that stage causing said grinding wheel to be made tangent to a known plane by dressing, said plane being located close to the desired tinished surface locus of the workpieees and being relatively remote from the initial un ground surface locus of the workpieees, and then causing the grinding wheel to be advanced by an always constant amount in cutting relation to the workpieces, which amount is greater than the lineal measure of the amount of reduction of the grinding wheel by the dressing device, such excess heing equal to the difference between the esti- :ziated wear and the actual wear of the grinding wheel, and finally causing the grinding to cease at the end of the last named advance, thus producing accuracy in a .series of grinding operations by measuring the finished surface from a dressing device located at a fixed point, said measuring being done just prior to completion of the grinding on a given article, leaving as the only variable the slight amount of wear of the grinding wheel during its short advance after ili'essingk Dated this fourth day of August, 1925.

. WALDO J. GUILD.