US2118304A - Grinding machine - Google Patents

Description

May 24, l938. l -c. J. HERTLEIN GRINDING MACHINE Filed 001'.. 5, 1936 2 Sheets-Sheet 1 ATTORNEYS May 24, 1938. c. J. HERTLEIN'- 2,M8,304

GRIND^1NG MACHINE Filed 001;.l 3, 1956 Sheets-Sheet 2 xNvENToR CARL J. HERTLEIN ATTORNEYS Patented May 24, 1938 UNITED STATES `rnfrlszfl-v'r OFFICE GRINDING MACHINE Application October 3,

25 Claims.

The invention relates in general to a grinding machine and specifically relates to thetcolfspindle and to the .associated motor `drive -o'f such machines; lto the mechanism for shifting the v`5 grinding tool vertically and to anorganization of control stops for limiting the travel ofthe -grinding tool.

The present application constitutes a'companion application to an adjustable work 'bed for supporting the work acted upon by the =tool and associated mechanism herein disclosedand lwhich application is entitled Adjustable workbedf, 'Serial No. 103,839 led October 3, 1936.

The primary object-of the invention vis y.to fimr prove and simplify -grinding machines =so as to provide among other things for both a coarse lfadjustment and setting of the grinding tool at Aan yoperative working position, 'as rwell as a rened micromical adjustment of zthe tool as circumstances vmay indicate as desirable, particularly in the control and presetting of the'limits olf movement of the tool in its vertically movable :direcftion during the coarser movements.

The invention has for'other objects the providing of easily fand quickly manipulated means for controlling the belt tension between the tool spindle and the motor for driving Ithe same; fthe providing of means for quickly releasing the 'tension y'to facilitate shifting-of 'the belt; the providing of stops for limiting the movement --of the spindle, which stops can 'be quickly reset into `approximate 'limiting yposition and thereafter more .accurately `set to minutely'limit the desired. `path of travel Io'f-thegrinding tool.

'Various other objects and advantages of the invention lwillbe in kpart obvious from an inspec- 'tion of the accompanying drawings and in part willbe vmore lfully set forth in the following particular description of one '-form of grinding-machine embodying the invention-andthe invention .also consists in certain new and novel "features of construction and combination of parts hereyinafter `set forth and claimed.

vIn vthe accompanying drawings:

Fig. '1 is a View largely in side elevation and with a .small portion at the bottom Aof the lcarriage broken away vto showthe lower plunger vstopandillustrating a lpreferred embodiment o'f the invention;

Fig. 2 is a view 'largely in iront elevation 0f the 'right Vside of the 'preceding ligure fand Vpartly yin vertical section taken fon 'the plane indicated byxthe line 2-2 of Fig, f1;

Fig. 3 isa rearelevationalviewflookingat Fig. 1 from the :right vside thereof;

Fig. 4 is a view in `sideelevation showing the side opposite vto -that shown A'in Fig. l1 and .with the upper portion .of the main column broken away-'to show parts-of the micrometer screw-feed;

Fig. 5 is a horizontal sectional view somewhat -5 enlarged and taken on the plane indicated -by the line '5-5 of Figs. '1 -and 4;

Fig.6 is a `detailed vertical sectional -view taken on the plane indicated by the line 6-6 of EFig-'5 looking in the-direction indicated byfthe arrow; Iand Fig. '7 `'is a detailed plane View of `the `stops shown kat Vthe-top of the carriage in Figs. l and-2.

In fthe drawings .there Ais shown 1a supporting `Atank I0 designed to holdthedrip lwater from the 15 tool. Mounted on a bed plate I I therein are two 'large -uprights, a vmain column il 2 :and a ffnulcrum standard I3. Themain column comprises a rugged casting including side fpla'tes 'I4 and VI5 connected across their 'fronts lby a face plate 'I6 provided with rforwardly projecting Iand .vertically extending guideways 2|"I and il 8, land 'merging 'into a wide spreading lbase I9. -Slidably mounted 'on .theLguideways :I-'I and vI8 is a vertically shiftable carriage '-20 of greater width than the face plate I6 .and side flapping the forward-edge portion Aof the side plates vIII and I5. I'he lcarriage .isienlarged at its `lower portion to forma 4forwardly extending 'horizontal extension 2| for supporting the grinding :tool Aand associated parts. The -eX- Itension 2| iis relatively wide Yas shown in Fig. '-2 .andhas supported thereon aspindle quill '22 in vwhich is rotatably mounted a tool spindle 23 projecting from one end of the quill. A .grinding tool l21! Iisreplaceably mounted on -theend of the spindle 523 following conventional practices in this respect. The opposite end lportion -of the spindle 'is provided with a driven multi-speed spindle pulley 25, the free end of which'is `journalled in -a bearing 26.

The front "face vof the carriage Z0 above vthe extension 2l is also provided with vertical guide ways i211 in which is slidably mounted the basev plate 28 of -an electric motor 29. The .motor shaft 'is provided with a spindle pulley '30 `in driving 45 'relation with .pulley 25 by means of a belt "31.

'Tension is maintained-'on the'beltby means of a coiled spring 32 positioned between Vthe extension 2`| and the underside of .the 'bracket33 "between'the `motor `29 yandtlre sliding vbase plate '28 50 las :best shown in Fig. 4. Opposite ends of the spring 32 are maintained in vertical vposition 'by a pair vof aligned spring guiding lingers 34 and y35, the lower nger 35 being :threaded and -prolvided Awith an adjustable nut 36 :forming lan :ad- :55

justable bearing for the lower end of the spring. The motor and its associated base plate is limited in its upward movement by the set screw 31 carried by a stop plate 38 at the top of the carriage and with its lower end engaging in a cup 39 formed on top of the motor. The set screw is secured in its vertically adjusted position by means of a binding screw 4t.

From this construction it is understood that the tension on the spring 32 is regulated by the manipulation of the nut 35 so as to cause the motor to bear upwardly against the screw 31 which has been preset to give the desired tension on the belt 3|.

For the purpose of releasing the tension on the belt where it is desired lto shift the belt on its pulleys to obtain variation in speed, a plunger 4I is caused to react between carriage and motor to lower the motor against the resistance of the spring 32. The plunger is actuated by a lever 42 pivoted to a bracket 43 carried by the stop plate 38 and to which the plunger is pivoted. The lower end of the plunger is received inl a, cup-like wear plate 44 similar to the cup 39 and likewise formed integral with the motor base plate In order to permit the displacement of th motor from the carriage, the stop plateA 38 is fulcrumed on a pivot pin 45 and arranged so that its free end 45 (see Fig. 7) normally held in place by a screw 45', may be moved forwardly about the pin 45 and swung out of the path ofthe base plate 28 and associated parts. In this way the motor can be slid upwardly until clear of the guideways and thus be removed from the carriage.

The carriage and with it the tool spindle and its driving motor may be moved up and down vertically as a single unit by means of a long, forwardly extending, manually-actuated lever 41 provided intermediate its length with a fulcrum nut 48 adjustably mounted in a slot 49 formed in the fulcrum standaid I3 and which nut is secured in adjusted position by means of a clamp controlled by a handle 58. The inner end of the lever 41 terminates in a bearing wheel 5I which is in sliding and lifting engagement with a wear plate 52 formed on the underside of the motor bracket 33. The lever is provided at its free end with a handle 53 and secured thereon between the handle and fulcrum is a counter weight 54 designed to balance substantially the weight of the motor carriage and associated Vertically movable parts.

From this construction it is understood that the fulcrum of the manually actuated lever is adjusted vertically along the standard I3 so as to bring the tool 24 in the region of the work to be ground and with the fulcrum set in place the operator by manipulating the lever may cause the grinding tool to operate bodily in a vertical direction while being rotated by the motor.

For the purpose of providing limits to the permissible vertical movement of the carriage when so actuated grossly by the manipulation of the lever, adjustable stops are provided between the carriage and the main column. For this purpose there is shown in Figs. l and a vertically extending channel plate 55 secured to the side plate I4. Vertically adjustable on the channel plate are two pairs of adjustable stationary stops numbered downwardly in Fig. l, 53 to 58. Referring to Fig. 5 it is noted that the stops are each secured in their relatively adjustable position by means of a binding nut 60 within the channel engaged by a headed screw 8l controlled by lever 82 (see top of Fig. 5). Each stop is provided with an offset 83 threaded through which is a vertical screw 64 secured in its adjusted place by a bind- "ing screw 55. In this way the vertical space between adjacent vertical screws of the pair of stops 55 and 51, for instance, may be accurately set first by roughly setting the stops on the main column and then adjusting the vertical screws. Similarly, when it is desired to control the tool travel t0 the lower portion of the machine, the lower pair of stops 58 and 53 may be utilized and the space between their associated vertical screws may likewise be accurately defined and located.

Operating in this space'as suggested in Fig. 1 is a carriage stop 55 comprising a plunger 'w31 urged forwardly by a spring 58. The plunger may be withdrawn into inoperative position against the tension of spring 58 by means of a head 69 particularly shown at the lower portion of Fig. 1. The plunger is provided with a Ylocking pin which, when the plunger is withdrawn may be rotated into position to bear on the adjacent surface 1I of the carriage to hold the carriage stop in its inoperative position. It is herein suggested that a second stop 12 of a similar plunger type be employed above the stop 66 and designed to operate between the upper pair of fixed stops 55 and 51 in those cases where it is desired to operate the grinding tool at relatively higher position off the base of the machine. In the showing in Fig. 1 the plunger of the upper stop 12 is withdrawn and locked in its inoperative position and thus has no control, for

the time being, on the possible movement of the carriage. Y

Considering the showing in Fig. 1 with the lower carriage stop operative and the upper carriage stop inoperative, it is understood that, by lower- `ing the lever handle from its horizontal position shown, the grinding tool may be elevated from its lowermost position, with plunger 51 engaging the top of the lowermost vertical screw into an elevated position for a distance defined by the length of the space'between the adjacent ends of the vertical screws forming parts of the stops 58 and 59.

In those cases where a more refined vertical adjustment of the tool spindleV and its associated motor is desired, a micrometer lead screw feed maybe employed. Such a feed includes a vertically extending lead screw 13 mounted at opposite ends in bearings 14 and 15 formed in the main column. A graduated hand wheel is positioned at the top of the machine and is connected through a worm and gear drive 11 with the lead screw 13 to rotate the same over angles measured on the scale 18. This lead screw is designed to be connected at will with the carriage by means of a split nut 19. The 'nut is formed of two halves which are mounted in a rectangular casing 88 encircling the lead screw. The two halves of the nut each include an outstanding top ange 8l which overlaps shoulders 82 formed in a pair of end closures 83 of the casing 88 to permit relative movement of the nut halves transversely of the lead screw while holding the nut from movement in all other directions. Opposing springs 84 and 85 bear on the two halves of the split nut and tend normally to force the nut into threaded engagement with the lead screw. The two parts of the split nut are arranged so as to be separated into their inoperative position, spaced from the lead screw by means of a pair of cams 8.6 positioned between the two .halves 'of the nut and moved to and .from .operative positi'onsibylmeansof a split nut lever ril?! in .the form The casing isl secured in a verti- .cally adjustable 'positionfonfthe :carriage ."bymeans ofa bindingfscrewll "extending through a verti- "cal-'slot 891m thecarriage. vThe screwfhasza'wide 'hea'dfll engaging the :inner sidepf the :carriage on :opposite sides of the 'slot'a's more particularly shown in Figs. 5 xand 16.

:In .operation .and :assuming 7that v`the split `nut s in its released, inoperative "position and vthat :it as .desired'to operate 'the ygrinding itool 'Within justmentr of :the stops, hereinbefore described, the `inanipulation'of .the long .controllever :Will raise or lower. the igrinding -.tool within ithe preset llimits tof rtravel. Should it be desired to workin atheupportion fof tthe :available space, forinstance,

yits associated cams inoperative a-nd Ithus, permit -theopposing spring'to move rthe split nut halves into engagement :with the lead screw, rafterwhich,

lby the Amanipulation of the graduated 'hand-Wheel .fat the .top of the .machina va 'rened adjustment in :the Vlocation .of the laxis of `the ygrinding tool .may be obtained. Asithis'micromical .adjustment .c'a'n'ibe obtained :at .fany'position within Vthe pervmissible Avertical :limits'gof movement of the tool,

l-it 1is possible Ito lquickly locatev the fgrinding v.tool in its approximate-'desired .position :by the rough coarse movement `.provided by the .lever :and then by `moving .the split nut .organization 4into lfeng'agement with lthe lead 'screw at :any position V.whel-ethe trough adjustment may havelocated .-it, a zrened variation in 'tool positions :may :be

quickly attained.

:During the .course of operating :the machine and wherein it may be desirable to change fthe .speed voi rotation of the .grinding tool tension on the belt may be-quic'kly released simply :by :pulling Vdown on the belt lever, :the .belt Amay be .shifted conventionally from .one to another pair Vof .pul-

leys, and releasing tension on'the plunger permit the elevating spring to restore tension on the-belt. 'Should the ybelt become too tight or itoo :loose iin practice, 'the adjusting screw-.at the '.top'of the --motor may be unlocked from .its previous vsetting, reset and :relocked lin its reset position.

By means of va ydevice Vsuch asis herein disclosed, extremely refined accuracy .in setting v'the grinding tool and in moving 'it .to and from .any

'preset locations vmay be :obtained quickly, where -quick shifting :is desired and in :moving 'it :over minute and restricted distances -maybe obtained -wherever accurate and :refined :work is desired.

'The stops ycontrolling'the vertical 'adjustment ofthe tool maybe further .used :as .when grinding .a number of tools which are similar vin that they containa number of diiferent areas ofthe same v--conformatio-n. For instance, the'rst area may .be ground with the plunger -l limited Ain its movement in `one direction by-stop 45-9. yThe second-area with plunger '12, 'for instance, is limited in one vdirection of movement by ystop :5-1; :the thirdarea again'using plunger-.651 Land limited in one direction of movement by stop 58 and so on. .In-general :all .that Tis necessary Eis toengage the proper plunger with .-the'proper .-.stoptoget all of the similarly located areas ground alike. yIn this way one preset arrangement .of the stops permits the identical grinding of any number vof Vtools for which the stops were Yinitially set.

When operating in connection .with the work supporting and locating bed .plate featured :in the companion application above identified, there 'is provided a precision grinding vmachine capable of accurately grinding lwork such as 4cutting tools of various'kinds and which in general is 'capable of accurately grinding a .multiplicity of 'different contoured surfaces.

While there have been shown, described and pointed out'in the annexed claims, certain novel features of the invention, it will be understood that various omissions,-substitutions and'changes 'in the form `and details of the deviceillustrated and in its operation may be made -by those vskilled in the art without departing from the spirit of the invention.

I claim:

1. In a grinding machine, the combination of a base provided with a main column and a 'fulcrum standard, a carriage slidably mounted ior vertical movement Von the column, a motor slidyably mounted for-vertical movement on the carriage, .a tool spindle journalled inthe lower portion of the carriage vbeneath ltheemotor for rotary movement about a horizontal axis, .a belt 'driving the spindle from the-motor, va'spring between the carriage-and motor tending to elevate vthe motor Aon the carriage, a .stop :between the 'motor and carriage :for limiting the upward movement ofthe `motor on .the carriage, ra lever "fulcrumed on the standard, having .a handle at one rend and at the other end engaging `beneath the motorto elevate the same together with the ycarriage 'on the ,main column.

2. In a grinding machine, 'the'combination of av base provided vwith a main column, a carriage slidably mounted `for vertical movement on the column, a motor slidably mounted `for vertical movement on the carriagepa tool spindle -journalled Vin the carriage beneath the motor `for rotary movement about Aa vhorizontal axis, a :belt .driving the spindle from Kthe motor, aspringg Abetween Ythe carriage and vrnotorvtending to elevate the motor on .the carriage, a vstop between Vthe motor and carriage for limiting-theupward movefulcrum adjustably mounted-in the standard, said lever being connected at one end to the carriage to move thesame vertically/'inthe guideway, having its other end providedwith an actuating han-Y dle and having a weight carried thereby between the handle and standardand tending to counterweight the carriage and parts carried thereby.

4. In agrinding machine, `the combination of a vertically disposed column .provided with'a guideway, a carriage mounted for sliding movement thereon, a grinding tool spindle :rotatably mounted in the carriage, Va standard and a manually actuated control lever .adjustably fulcrumed 4.to

the standard and operatively :connected V.to ,the

carriage to `move the tool spindle 'vertically rover distances controlled by the location of the lever fulcrum.

5. In a grinding machine, the combination of a structural part of the machine, a tool spindle mounted therein for rotary movement, a motor, a belted connection between the motor and spindle, a spring reacting between the motor and structural part for placing tension on the belted connection, and means for regulating the tension placed on the belted connection.

6. In a grinding machine, the combination oi a vertically disposed main column provided with a guideway, a carriage slidably Vmounted for vertical movement on the guideway, a tool spindle journalled in the carriage for rotary movement, an electric motor slidably mounted for vertical movement on the. carriage and provided with a multi-speed pulley in belted driving engagement with the spindle in all positions thereof, means for adjusting the location ci' the motor on the carriage thereby to set it relative tothe spindle and manually actuated means engaging the carriage for shifting the spindle and motor when so relatively adjusted, together vertically as a unit and a resilient support between the motor and carriage acting to maintain tension on the belt.

7. In a grinding machine, the combination of a carriage mounted for vertical movement, a grinding spindle mounted for rotary movement in the carriage and provided with a driving pulley, a motor guided for vertical movement on the carriage and provided with a pulley, a belt forming a driving connection between the motor and spindle pulleys, a coiled spring located between the carriage and motor, tending to elevate the motor upwardly away from the spindle and thus place tension on the belt and adjustable means for limiting the elevating movement of the motor under the tension from the spring.

8. In a grinding machine, the combination of a carriage mounted for vertical movement, a grinding spindle mounted for rotary movement in the carriage and provided with a driving pulley, a motor guided for vertical movement on the carriage and provided with a pulley, a belt forming a driving connection between the motor and spindle pulleys, a coiled spring located between the carriage and motor, tending to elevate the motor upwardly away from the spindle and thus place tension on the belt and adjustable means for limiting the elevating movement of the motor under the tension from the spring, and manually actuating means for lowering the motor against the tension of said spring to release the tension on the belt and thus permit easy shifting of the belt on its pulleys.

9. In a grinding machine, the combination of carriage mounted for vertical movement, a grinding spindle mounted for rotary movement in the carriage and provided with a driving pulley, a motor guided for vertical movement on the carriage and provided with a pulley, a belt forming driving connection between the motor and spindle pulleys, a coiled spring located between the carriage and motor, tending to elevatev the motor upwardly away from the spindle and thus place tension on the belt, means for limiting the elevating movement of the motor under the tension from the spring, manually actuating means for lowering the motor against the tension of said spring to release the tension on the belt and thus permit easy shifting of the belt on its pulleys, and manually actuated means for elevating the motor and in causing the motor to bear against said stop Vto act therethrough to lift the carriage with its associated tool spindle.

10. In a grinding tool, the combination of a spindle, a spindle quill therefore, a spindle pulley in driving engagement with the spindle, a motor provided with a spindle pulley, a belted connection between the two pulleys and a spring between the quill and motor, tending to support the motor from the quill and reacting between the spindle and motor tending to place the belt under tension, and an adjustable stop for one end of the spring for varying the tension of the spring and thus varying the tension of the belt.

1l. In a grinding machine, the combination of a carriage, a spindle quill carried thereby, a spindle rotatably mounted in the quill, a spindle pulley journalled in the carriage and in driving engagement with the spindle, a motor mounted for vertical movement, a motor pulley, a belt connecting the two pulleys, a spring engaging the motor and urging the same upwardly against the tension of the spindle pulley, means for varying the tension of the spring, a stop for limiting the upward movement of the motor, and a plunger reacting between the carriage. and motor to' lower the motor against the spring tension thereby to release the tension on the belt.

12. In a grinding machine, the combination of a carriage, a spindle quill carried thereby, a spindle rotatably mounted in the quill, a spindle pulley journalled in the carriage and in driving engagement with the spindle, a motor mounted for vertical movement, a motor pulley, a belt connecting the twol pulleys,V a spring engaging the motor and urging the same upwardly against the tension of the spindle pulley, means for varying the tension of the spring and an adjustable screw stop for limiting the upward movement of the motor, a plunger reacting between the carriage and motor to lower the moto-r against the spring tension thereby to release the tension on the belt, and said plunger and adjustable stops mounted to be shifted into an inoperative position clear of the path of upward movement of the motor, thereby to permit the motor to be lifted off the carriage.

13. In a grinding machine, the combination of a main column provided with a pair of vertically adjustable and relatively stationary stops, a tool supporting carriage mounted on the column for vertical movement, said carriage provided with a stop operable between the pair of stationary stops to limit the vertical movement of the carriage in both directions and means for raising and lowering the carriage, and said carriage stop constituting a spring pressed plunger adapted to be retracted into .an inoperative position free of the stationary stops.

14. In a grinding machine, the combination of a grinding tool supporting carriage guided for vertical movement, two means each operatively connected to the carriage to shift it vertically independently of the other.' one of said means comprising a manually actuated lever for quick shifting into an approximately correct position and theothercomprisingamanually actuated micrometer lead screw for refined adjustment of the carriage into the desired correct position and control means for connecting and disconnecting said lead screw from the carriage at will and resisting actuation by the lever when connecting the lead screw with the carriage and said lever permitting actuation of the carriage by the lead screw.

15. In a grinding machine, the combinationV of a maincolumn, a carriagemountedthereon for vertical movement, a grindingtool mounted :for rotary movement in thecarriage, mechanism for shifting vthe carriage and withit the grindingtool vertically on the column, said mechanism including la 4vertically yextending lead screw mounted in the column, manually actuated means for rotating the -lead screw, a two-part split nut mounted in the carriage and adapted to engage the lead screw whereby the rotation of the lead screw will shift the carriage vertically, means including a vertical slot in the carriage and a binding screw carried by the nut and extending through the slot for adjustably securing the split nut to the carriage at any position along the length of the lead screw, and control means for moving the two parts of the split nut to and from their operative engagement with opposite sides of the lead screw.

16. In a grinding machine, the combination of a grinding tool, mounted for rotary movement about its axis and for shifting the tool vertically, a support for said tool, manually controlled mechanism for minutely shifting the support and with it the grinding tool into a desired position, said mechanism including a vertically extending lead screw mounted for rotary movement and otherwise fixed relative to the support, a split nut for engaging the feed screw, a casing for the split nut provided with means for securing the split nut to the tool support in vertically adjusted position relative to both the support and the lead screw and resilient means between the casing and split nut tending to maintain the nut in engagement with the lead screw.

17. In a grinding machine, the combination of a grinding tool journalled for rotary movement about a horizontal axis, a at plate constituting a vertically shiftable carriage for supporting the same, a manually actuated lever for shifting the carriage vertically, a lead screw and split nut organization for shifting the carriage vertically, said organization including a casing, means for detachably securing the casing to the carriage at will, a two-part split nut slidably mounted in the casing, means tending to cause the two parts of the nut to engage the lead screw and control means for moving the split nut from its operative engagement with the lead screw.

18. In a grinding machine, the combination of a carriage mounted for vertical movement, a grinding spindle mounted for rotary movement in the carriage and provided with a driving pulley, a motor guided for vertical movement on the carriage and provided with a pulley, a belt forming a driving connection between the motor and spindle pulleys and a coiled spring located between the carriage and motor for resiliently supporting the motor from the carriage and means for adjusting the tension on the spring thereby to regulate the tension on the belt.

19. In a grinding machine, the combination of a main column provided with a pair of vertically adjustable and relatively stationary stops, a tool supporting carriage mounted on the column'for vertical movement, said carriage provided with a stop operable between the pair of stationary stops to limit the vertical movement of the carriage in both directions and the stop on the carriage including a spring pressed element disposed normally in line between the pair of stops on the column and said element adapted to be withdrawn from said path to permit the carriage to be moved independently of the stops.

20. In a grinding machine, the combination of a column provided with two pairs of vertically adjustable vand `relatively stationary stops, a tool supporting carriage mounted on the column for vertical-movement, ksaid vcarriage provided with two stops, one for each pair 'of stationary stops and/each arranged for limiting,V the vertical `movement of the carriage in both directions when located between its associated stationary stops and each carriage stop movable into an inoperative, out of the way position whereby either of the two sets of stops may be utilized at will to control the limits of permissible movement of the carriage.

21. In a grinding machine, the combination of a main column, a carriage slidably mounted on the column for vertical movement, a grinding tool journalled in the carriage for rotary movement about an axis iixed relative to the carriage, means including adjustable stops acting between the carriage and column for limiting the extent of and for locating the permissible location of travel of the carriage and thus of the tool axis, manually actuated means for quickly and roughly locating the carriage to bring the tool axis approximately into a desired position and manually actuated micrometrical feed means acting on the carriage when so roughly located to bring the tool axis more accurately into the desired position.

22. In a grinding machine, the combination of a main column, a carriage slidably mounted thereon for vertical movement, a grinding tool journalled on the carriage for rotary movement, a channel plate carried by the column, a plurality of stops vlocated on the channel plate, means for adjusting the stops relative to each other, means for locking the stops in their adjusted positions, a set screw carried by each stop, means for locking each set screw to its associated stop and a manually actuated retractable stop carried by the carriage and disposed when in operable position between a pair of said set screws and disposed when in an inoperative position clear of the stops on the channel plate.

23. In a grinding machine, the combination of .a main column, a carriage slidably mounted thereon for vertical movement, a grinding tool journalled for rotary movement on the carriage and movable vertically therewith, means for controlling the limits of movement of the grinding tool while operating in two zones of movement, said means comprising a channel plate carried by the column, four relatively stationary stops slidably mounted on the channel plate, one above the other, means for securing each stop to the channel plate, each stop provided with a set screw and with the two upper and the two lower set screws facing each other to form two adjustable space dening means, the carriage provided with two retractable stops, one spaced above the other and both adapted to operate in either of the spaces defined by the upper or lower pairs of relatively fixed stops whereby with one setting of the relatively fixed stops the carriage may be operated selectively in either a high or a low zone of operation.

24. In a grinding machine, the combination of a carriage mounted for vertical movement, a grinding tool journalled for rotary movement on the carriage and movable vertically therewith, a motor for driving the tool provided with a base slidably mounted on the carriage for vertical movement, an adjustable stop between the carriage and motor base for locating the motor in a preset position on the carriage and means reacting between the motor base land carriage for forcing the motor into said position prefixed by the adjustment of the stops.

25. In a grinding machine, the combination of a carriage mounted for Vertical movement, a grinding tool journalled for rotary movement on the carriage and movable vertically therewith, a motor for driving the tool provided with a base slidably mounted kon the carriage for vertical movement and'an adjustable stop between the carriage and motor base for locating the motor in a preset position on the carriage, said stop being movable into an inoperative position to permit the motor and its base to be slid ofi the carriage.

CARL J. HERTLEIN.

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