USRE22953E - Gear testing apparatus - Google Patents

Description

Dec. 23, 1947. w. s. PRAEG GEAR TESTING APPARATUS Original Filed April 17, 1939 4 Sheets-Sheet 2 I INVEN TOR.

ALTER $.PRA G Wain W )L ATTORNEYS Dec. 23, 1947. w. s. PRAEG I GEAR TESTING APPARATUS 4 Sheets-Sheet 5 Original Filed April 17, 1939 .F IG. 6.

' INVENTOR. w LYER S.PR 6 BY W TTORNEYS mun mm A G P N 11 w E W T R A E G Original Filed April 17, 1939 4 Sheets-Sheet 4 INVENTOR.

6% m m A R E) mm A W M Y 8 relative translation Reiecned Dec. 23, 1947 UNITED STATES PATENT OFF-ICE om 'ras'rmo menu-us Walter S. Prneg. National Brooch Mich., a corporation of Detroit, Mlola, listener to & Machine Company, Detroit,

Michigan Original No. 2,202,638, dated May 28, 194., Serial No. 268.413, filed 15 Claims.

The manufacture of gears'with cut teeth has I developed in the last fifteen years from an entire dependence upon the machine Operator to a coordination of efiort on the part of the operator and the men in a gear laboratory; this lab-. oratory being equipped with the most sensitive measuring equipment available for measuring elements of gear teeth. In all gears it is necessary that the teeth bear a proper relationship to the axis of the gear. In spur gears the teeth must be paralleled in all planes with the axis of the gear. In helical or spiral gears the teeth must have a uniform helical advance around the axis of the gear, one complete revolution of helical advance being known as the lead of the gear. The angular relationship of the pitch line on the gear to its axis is known as its helix angle.

A number 01' different designs or lead measuring machines are available, all Of which are compllcated in mechanism and slow to set up and operate. This does not offer any serious difiiculty when only one piece is to it is necessary to measure leads on a number of pieces the time consumed to do this work becomes a serious factor.

A very satisfactory way to measure lead is to check a lead against a known lead. This is accomplished very simply by the apparatus disclosed in the present application.

Briefly described, a master element, which may be in the form of a gear or a cylindrical element having one or more helical slots of known angle formed therein, is mounted to be rotated with the gear to be tested. A movable assembly comprising a relatively fixedly mounted tip to engage the master element and a movable tip to engage a tooth of the gear being tested is provided. As between the master element and the gear on the one hand and the tips referred to on the other hand takes place, movement of the movable tip indicates deviation between the angle of the tooth being measured and the corresponding surface or the master element.

It is accordingly an object of the present invention to provide a measuring apparatus for measuring angles or crowning of gear teeth.

It is a further object of the present invention to provide apparatus of the character described, characterized by its extreme simplicity and by its efllciency and rapidity in operation.

It is a further object of the present invention be measured. When Aprll for reissue filed Septe 17, 1989. Application miner 30, 1946, No.

scribed embodying numerous improved elements of design.

Other objects of the invention will be'apparent as the description proceeds, and when taken in conjunction with the accompanying drawings wherein:

Figure 1 is a perspective of my improved apparatus;

Figure 2 is an enlarged detail plan view showing the cooperating elements;

Figure 3 is a fragmentary vertical section through the carriage of my apparatus:

Figure 4 is a section on the line 1-4, Figure 3:

Figure 4A is a section on the line lA-4A, Figure 4;

Figure 5 is a detail section of a contact element;

Figure 6 is an enlarged fragmentary section on the'line 88, Figure 3:

Figure 7 is an enlarged iragmentary section on the line 1-1, Figure 3:

Figure 8 is a detail elevation of a modification employed for testing a gear provided with an integral shank;

Figure 9 is a side elevation partly in section of the structure shown in Figure 8: and

Figure 10 is a perspective of the master guiding element.

Referring to Figure 1, the apparatus comprises a table Ill provided with ways It along which are adjustably mounted in clamping relation a pair of stocks l2 and It for receiving therebetween in rotatable relation a master element It and a gear or other article to be tested II. Suitable clamping means indicated at It are provided.

and in addition a spindle lock nut I1 is carried by the stock II. The master element It and the gear I! are retained in non-rotatable relation on an arbor it, which in turn is mounted for free rotation between the stocks I! and I3.

Carried by the table it) and adjustable thereon in ways I! toward and away from the spindle I8 is a pedestal 20 provided with suitable guiding ways indicated generally at 2|. Mounted on the ways is a carriage 22 which supports a contact member II carrying a contact element 24 adapted to'engage a tooth of the guiding element ll. Member 23 is ustable toward and away from the master elment It and is adapted to be locked in adjusted position by a clamping screw or the like 25.

The carriage I2 is provided with ways 28 on which is mounted an indicator support 21. The

from the contact member 23 and is adapted to be locked in adjusted position by suitable clamping means provided with a manually operable handle 20. Carried by the indicator support 21 is an indicator mounting 30, best shown in Figure 3. A measuring pointer 3 I is movably mounted on the indicator mounting and is adapted when moved to move an indicator actuator 32. This actuator is adapted toengage one of the indicators 33 or 34 which in turn give a direct reading of the deviation between the angularity oi the surface being measured and the angularity of the corresponding surface of the master element I4.

Referring now to Figures 4 and 4A, the pedestal 20 is provided with locking means comprising a shaft 40 carrying a lock handle 4| and an eccentric 42 which in turn is associated with a locking pin 43 adapted to actuate the clamp 44, movable in the ways I3 previously referred to. The shaft 45 is retained against axial movement by a, lock screw 45 movable in a circumferential 'groove 45.

This arrangement provides for movement of the pedestal 20 bodily toward and away from the ways II and for rigidly retaining the pedestal in adjusted position. The indicator support 21, as shown in Figure 4, is movable toward and away from the contact member 23 along ways 23 and is adapted to be clamped in adjusted position by means of a clamp 41 cooperating with a locking member 28. The indicator support 21 is provided with clamping means to carry a rod 48 which supports the indicator mounting 30, The indicator support 21 is provided with a rigidly supported guiding plate 43 movable in the ways 25. In addition a second key 50 is bolted to the underside of the indicator support 21 and is provided with a pair of recesses 5| which receive compression springs 52. The indicator support 21 is provided with a halfround recess 53 for receiving the rod 40, and a second plate 54 is provided. also formed to provide a half-round recess for the rod. Springs 52 urge the plate 54 resiliently toward the indicator support and serve to clamp the rod 43 resiliently therebetween upon release of the clamping member 25. The spring compression is sufficient to prevent accidental rotation of the rod 43 with possible consequent cators carried thereby. when clamp 41 is tightened plate 54 firmly locks rod 48 in adjusted position at the same time as it looks indicator support 21 in adjusted position in ways 25.

Referring now particularly to Figure 3, the indicator support and mounting is shown in detail. The indicator mounting is clamped on the rod 45 as by a clamp screw or the like 55 (Figure 2). This arrangement permits adjustment about the axis of rod 43 to position the axis of lever 53 generally parallel to the surface being measured. The indicator mounting comprises a centrally apertured member 55 bolted or otherwise secured to a lower housing member 51, The housing member 51 is shown in detail in Figure I and is provided with a recess 55 for pivotally supporting a lever 53 which carries the measuring pointer 3| and the indicator actuator 32. Preferably, in order that this lever shall be freely supported with a constant force applied thereto, it is provided with a pair of spring pressed centers 50 and 5 I, the spring being shown in Figure '1 and indicated at 52. The center 50 may be locked in adjusted position by a set screw 63, shown in Figure 3. centering bolts 54 being provided in the housing '51.

As shown in Figure 3, the indicator actuator 32 bolted thereto and having a key damage to the sensitive indipasses upwardly through the central aperture referred to in the member 56 and clearance is provided for movement of the actuator 32. The member 56 is provided with a pair of diametrically oppositely extending slotted ears 65 to which may be bolted indicators 66, which may be of conventional design.

In order to provide for free movement of the carriage 2 2 the ways 2I comprise removable ball bearing races 10 and a cooperating cage 1I containing ball bearings. The cage is shorter than the races 10, as indicated in Figure 6, and stop plates such as indicated at 13 are provided, with the result that the cage is substantially self-centering.

Means are provided for translating the carriage 22 along the pedestal 20 and takes the form of a rack 15 bolted to the pedestal 20. The carriage 22 has mounted therein a pinion 16, shown in Figure 3, which is in constant mesh with the rack 15. A handwheel 11 is provided and is adapted to rotate the gear 15 through suitable cooperating reduction bevel gearing indicated at 13. As will be evident. rotation of the handwheel results in a relatively slow controlled translation or the carriage 22.

Referring now to Figure 5, I have illustrated in detail the arrangement of the contact member 23, which is slidably received in the correspondingly formed aperture in the carriage 22. The member 23 may be clamped in adjusted position. as Previously referred to, by the member 25. The contact member 23 is tubular and is adapted to receive slidable rod 30 which is connected to a threaded member BI for movement therewith. Member 3| is threadedly received within the tubular member 23, the screw threads being indicated at 52.

The contact element 24, which is adapted to en- I gage the guiding surface of the master element I4, is integrally formed on a short rod section 04 and is likewise slidable in the bore of the tubular member 23. A flange is formed thereon and is adapted to cooperate with a cap member 06 threadedly received on one end of the member 23. The relationship is such that upon loosening the cap member 83 the contact element 24 may be adjusted toward or away from the master element I,4 by a suitable rotation of parts may be rigidly retained in adjusted position by screwing the cap 05 inwardly while retaining member BI against rotation. By this means the contact element 24 may be brought into predetermined relation with the guide surface.

The mechanism just described is suitable for measuring gears which may be mounted upon the arbor I3 either directly or by means of suitable conventional adapters. In the event that the gear to be tested is formed integrally with a shaft, other provisions must be made. Mechanism for taking care of this situation is illustrated in F18- ures B to 10.

In these figures I have illustrated a head I00 which is adjustable toward and away from an oppositely disposed head. The work piece is adapted to be supported for rotation between the heads and to be rigidly retained for rotation with a master element I08. For this purpose the head I00 is provided with a central bore I02 in which is received a centrally apertured block I03 adapted to be rigidly-clamped in the bore I02 by means of a cooperating nut I04, as clearly illustrated in Figure 9. Annular member I05 is mounted for rotation relative to the relatively fixed block I03,

the member BI. The e its clearance. may be appropriate ball bearings indicated at being provided for this purpose. III is rotatably mounted on the III and is adapted to be clamped I and I" annular member in adjusted position thereon by means or a clamping screw I00, or

the like. Master element I00 is illustrated in detall in Figure andjhas formed thereon one or more helical slots or grooves III which, as seen in this figure, may be section. Accordingly, adjustment of contact element 24 inwardly or outwardly, as previously deof inwardly tapered cross- Master element measured or the master element to accommodate diiierent diameter parts; It will thus be seen that the device is extremely flexible and within the limits or-the machine may be adjusted to take scribed, varies its clearancein theslot so that greater than the clearance between measuring pointer ii and the surface which it engages. plurality of helical slots III may be provided, each extending ata different helix angle to the axis of the member I08, as illustrated in Figure 10. A plate "2 is bolted to the annular member I05, a rigid center H3 bein formed or secured on the forward face of the plate II2. A driving member H4 is rotatably mounted about plate H2 and is adapted to be clamped thereto in adjusted position by a set screw 5. Formed on the for ward face of the annular member II4 are a pair of projections I I5, each provided with a set screw II1 which functions to receive a driving connection rigidly secured to the gear being tested.

In order to obtain a rigid assembly, an expanding adapter I I0 is provided in the correspondingly formed central passage through the block I03. The adapter IIB, asindicated at I I 9, is slotted by a pair of diametrically opposite slots extending completely through the adapter. The adapter H8 is threaded as indicated at I20 and as clearly shown in Figure 9 the arrangement is such that the headed portion I2I of the adapter II 8 retains the relatively rotary portions of the assembly in position. Also as shown in the figure, the headed portion I2I cooperates with the suitably formed portion of the member I05 to form a race for the ball bearings I01. The adapter III! is centrally apertured as indicated at I23, and this central aperture has a tapered portion I24 adapted to cooperate with a wedging ball I25. A socket set It will be understood that ascrew I28 is threaded into the passage I23, as indicated in Figure 9, and as will be apparent is adapted to force the ball I25 against the conical surface I24. This expands the adapter H8 at its slotted portion and provides for an extremely rigid relationship between the adapter H8 and the block I03. Preferably and as indicated in Figure 9, the adapter II 8 is provided with a recess I21 formed to receive a screw driver, or the like, for assembly.

In this device as in the modification previously described, clamping means I20 are provided for clamping the head I 00 in adjusted position in the ways II.

From the foregoing detailed description the operation of my improved construction will bereadily apparent. The heads I3 and I2 or I00 may be adjusted along the ways II to accommodate any convenient length'of device to be tested within the limits of the machine. In a like manner the pedestal 20 may be adjusted toward and away from the ways II to accommodate any diameter of device to be tested Within the limits of the machine, In like manner the indicator support 21 may be adjusted relative to the carria e 22 to provide for any convenient spacing between the contact element 24 and the measuring pointer 3|. In like manner both the indicator mounting l0 and the contact member 23 may be relatively adjusted toward and away from the device being care of a wide variety of parts.

Referring more particularly to Figure 3, it will be noted that in the preferred form a pair of indicating devices 38 and 34 are provided. Preferably clearance is'provided between the indicator actuator 32 and the cooperating portions of the indicators so that the indicator actuator 22 W11. cooperate with but one of the indicators. The arrangement permits measurement of either side of a tooth space without further adjustment of the apparatus. As is well understood, indicators of the type shown have projecting elements which are urged outwardly by spring'means. By obtaining a suitable relative adjustment between the master element I4 and the gear or other element being measured, it is possible to provide an initial contact between the indicator actuator 02 and either of the spring pressed elements 90. The spring which urges the element 50 into engagement with the indicator actuator 32 also biases the lever 59 to retain the measuring pointer ii in contact with the surface being measured- The parts may be adjusted to the position indicated and the indicating pointer, if desired, set to zero. At this time rotation of the handwheel 11 may take place-with a corresponding slow translation of the carriage 22 relative to the master element l4 and the work piece. If a helical element is being measured, and'if a helical slot on the master element is engaged by the contact element 24, it will be apparent that this slow translation of the carriage 22 will result in a corresponding rotation of the master element I4. Since the master element I4 and the work piece, such as the gear ii, are rigidly mounted for simultaneous rotation, rotation of the master element will result in a. corresponding rotation of the work piece. As long as the helical-surfaces under consideration are inclined equally, there will be no motion of the measuring pointer 3I and consequently no movement of the pointer on the dial of the corresponding indicator. If. however, there is a, difference between the angularity of the two helical surfaces under consideration, there will be a corresponding relative movement of the measuring pointer 3| which will be trans formed to a corresponding indication on the dial of the indicator. Having due regard to the constants of the machine for any particular setting, this reading of the indicator may be translated directly into difference in angularity of the helical surfaces or irregularities therein, and the like.

It is desired to emphasize at this time another important function of the present apparatus. As is well understood. it is common practice today to employ crowned gears; that is, gears having teeth which are longitudinally bowed from end to end. Teeth of this. type offer numerous important advantages over uncrowned teeth, and the field of their use is constantly increasing. The

' present apparatus provides a convenient means with an unmodified helical surface, in which case the desired crownin of the teeth of the work passage I 5 would beindicated by a predetermined movement of the pointer on the corresponding indicator. The last method is in many ways pre- I tus adapted for measuring ferred since the same master element may be employed for measuring or comparing variously crowned teeth having the same helix angle.

As I have indicated in the previously described drawings, the master element is provided with helical teeth or slots. It will be understood that the apparatus is adapted equally well tov measure straight or spur teeth on a gear. In this case translation of the carriage i2 will not be accompanied by rotation of the master element II but any departure from parallelism in the teeth of the gear I! will be at once evident from a corresponding movement of the pointer on the indicator in use. It will of course be obvious that in like manner crowning oi spur teeth on the work piece II may be measured by comparing the surface of an unmodified spur tooth on the master element It or, if preferred. with a correspondingly crowned spur tooth on the master element N.

Contact element 2| is preferably of such a size relative to the slot ill, or effective tooth space (where amaster element such as it, Figure 1, is employed) that more clearance exists therebetween than between measuring pointer 31, and the surfaces with which it engages. As a result, translation of the carriage in one direction will measure the surface of one tooth. and reverse translation will measure the adjacent surface of the next tooth, the excess clearance allowing lever 59 to rock so that indicator actuator 12 may move away from one indicator element 90 to contact the other. This greatly facilitates complete checking ofa gear, and is an important feature of the present apparatus.

I have disclosed the present apparatus as particularly useful in measuring of gears. but it will be evident that its function is not so limited, and it is therefore intended to cover broadly apparaor comparing surfaces.

While I have illustrated and described several specific embodiments of my invention, it will be apparent to those skilled in the art that various additions, modifications, omissions, combinations and substitutions may be made which will be within the spirit and scope of my invention as defined by the appended claims.

What I claim as my invention is:

1. A comparator comprising a rotatable master element having a peripheral slot therein inclined to the axis of said element, means for rotatably mounting said element, means for mounting a work piece having a similar slot for rotation with said. element, a rigid member engaging a surface, of the slot in said element, means for relatively moving said member and element in a direction parallel to the axis of said element to rotate said element and said work piece, and measuring means occupying a fixed position relative to said rigid member and relatively movable therewith with respect to said element and work piece, for comparing a. surface of the slot in said work piece with the surface of the slot in said element engaged by said rigid member, said measuring means comprising a lever having an end engaging the surface of the slot in said work piece, and a device to indicate the extent of movement of said lever.

. 2. A comparator comprising a rotatable master element having a peripheral slot therein inclined to the axis of said element, means for rotatably mounting said element, means for mounting a work piece having a similar slot for rotation with said element. a rigid member engaging a surface of the slot in said element, means for relatively moving said member and element in a direction parallel to the axis of said element to rotate said element and said work piece, and measuring means occupying a fixed position relative to said rigid member and relatively movable therewith with respect to said element and work piece, for comparing a surface of the slot in said work piece with the surface of the slot in said element engaged by said rigid member, said measuring means comprising a pivoted bell crank, one arm of said crank having an end engaging the surface of the slot in said work piece, and a device for indicating the-extent of movement of the other 7 arm of said crank.

3. A comparator comprising a rotatable master element having a peripheral slot therein inclined to the axis of said element, means for rotatably mounting said element, means for mounting a work piece having a similar slot for rotation with said element, a rigid member engaging a surface of the slot on said element. means for relatively moving said member and element in a direction parallel to the axis of said element to rotate said element and said work piece, and measuring means occupying a fixed position relative to said rigid member and relatively movable therewith with respect to said element and work piece, for comparing a surface of the slot in said work piece with the surface of the slot in said element engaged by said rigid member, said measuring means comprising a bell crank having an arm engaging the surface of the slot in said work piece, and a device for indicating the extent of movement of the other arm of said crank, said measuring means being adjustable about an axis perpendicular to the axis of said work piece to position the axis of said bell crank substantially parallel to the surface of the slot in said work piece engaged by said bell crank.

4. A comparator comprising a support, a pair of centers adjustable toward and away from each other to accommodate a pair of elements to be compared, a pedestal adjustable toward and away from said centers, a carriage movable on said pedestal parallel to the axis of said centers, a contact element carried by said carriage and adapted to engage a surface of one of said pair of elements, an indicator support adjustable on said carriage toward and away from said contact element, an indicator mounting on said indicator support, a movable measuring pointer carried by said mounting, and an indicator adapted to be actuated by said measuring pointer.

5. A comparator comprising a support, a pair of centers adjustable toward and away from each other to accommodate a pair of members having surfaces to be compared, a pedestal adjustable toward and away frcm said centers, a carriage movable on said pedestal parallel to the axis of said centers, 9. contact element carried by said carriage and adapted to engage a surface of one of said pair of members and adjustable on said carriage ,toward and away from said one member, an indicator supportadjustable on said carriage toward and away from said contact element, anindicator mounting on said indicator support adjustable on said support toward and away fromsaid other member, a movable measuring pointer carried by said mounting, and an indicator adapted to be actuated by-said measuring pointer.

6. In a comparator, a carriage, a contact element on said carriage, ways on said carriage, an

axis of said element, and

' by one of said supports ter moss

l rotation with said element, a rigid member enaging a surface oi the said one slot on said element, means for relatively moving said eleindicator support on said carriage mounted in said ways for adjustment toward and from said contact element, an indicator mounting adjustably carried by said indicator support, clamping means for rigi ly retaining said indicator support in adjusted position on said ways, and for simultaneously rigidly retaining said indicator mounting in adjusted position in said indicator support.

7. In a comparator, a carriage, a contact element on said carriage, ways indicator support on said carriage mounted in said ways for adjustment toward and from said contact element, an indicator mounting adjustably carried by said indicator support, clamping means for rigidly retaining said indicator support in adjusted position on said ways, and for simultaneously rigidly retaining said indicator mounting in adjusted position in said indicator support, and yieldable means efi'ective onlyon release of said clamping means for retaining said indicator mounting against accidental displacement.

8. A comparator comprising a rotatable master element provided with a peripheral helical slot, means for mounting said element for rotation, means for supporting a slotted work piece to be checked for rotation with said element, a member extending into the slot of said master element and engageable with either side 01' said slot, means for relatively translating said element and member in a direction parallel to the measuring means having a part extending into the slot of said work piece. said member having more clearance in its slot than said part.

9. A comparator comprising a rotatable master element provided with a peripheral helicalslot, said slot being of tapered cross-section, means for mounting said element for rotation, means for supporting a slotted work piece to be checked for rotation with said element, a member extending into the slot of said master element and engageable with either side of said slot, means for relatively translating said element and member in a direction parallel to the axis of said element, and measuring means having a part extending into the slot of said work piece, said member being independently adjustable toward and from said element to vary its clearance in said tapered slot.

10. Apparatus for comparing the surface 01' a work piece with a similar surface on a master element which comprises means for mounting said work piece and master element for rotation in axially spaced relation, said work piece and element being locked together for simultaneous rotation, means mounting a pair of supports spaced apart by the amount oi axial spacing of said work piece and master element, a finger rigidly carried and adapted to engage one of said surfaces,. a finger movably carried by said other support and adapted to engage said other surface, a measuring device to measure movement of said movable finger, and drive meansincluding reduction gearing for relatively moving said first two means in a direction parallel to the axis of rotation of said master element and work piece.

11. A comparator comprising a rotatable maselement having a plurality of peripheral slots extending at difierent helical angles therein, means for rotatably mounting said element, means ior mounting a work piece having a slot similar to one or the slots in said element for on said carriage, an

a direction parallel tothe axis 01' said element to rotate said element and said work piece, and measuring means occupy ing a fixed position relative to said rigid member and relatively movable therewith with respect to said element and work piece, for comparing a surface of the slot in said work piece with the surface oi the said one slot in said element engaged by said rigid membe 12. A comparator comprising a base, a rotatable master element having a plurality oi peripheral helical slots extending at difierent helical angles therein, means for rotatably supporting said element on ing a work piece having a slot similar to one oi the slots in said element for rotation with said element, ways on said base parallel to the axis of said element, a carriage slidable on said ways, a rigid member fixed on said carriage engageable with a suriace of the said one slot on said master element, measuring means on said carriage including a part engageable with a surface of the slot in said work piece, and means for moving said carriage in said ways.

13. A comparator'comprising a. base, a master element having a peripheral slot therein inclined to the axis of said element, means for rotatably supporting said element on said base, means ment and member in for supporting a work piece having a similar slot for rotation with said element, ways on said base parallel to the axis oi said element, a carriage slidable on said ways, a member fixed on said carriage and engaging said surface, measuring means on said carriage operatively associated with said work piece, and means for moving said carriage in said ways, said measuring means comprising a movable part adapted to engage a surface of the slot in said work piece, and a device to indicate movement of said member, said means for moving said carriage comprising a meshing rack and pinion and manual means for rotating said pinion.

14 A comparator comprising a, base, a master element having a peripheral slot therein inclined to the axis of said element, means for rotatably supporting said element on said base, means for supporting a work piece having a similar slot for rotation with said element, ways on said base parallel to the axis of said element, a. carriage slidable on said ways, a member fixed on said carriage and engaging said surface, measuring means on said carriage operatively associated with said work piece, and means for moving said carriage in said ways, said measuring means comprising a movable part adapted to engage a suri'ace oi the slot in said work piece, and a device to indicate movement of said member, said means for moving said carriage comprising a, meshing rack and pinion and manually driven reduction gearing for rotating said pinion.

15. A comparator comprising a base, a master element having a. peripheral slot therein inclined to the axis of said element, means for rotatably supporting said element on said base, means for supporting a work piece having a similar slot for rotation with said element. ways on said base parallel to the axis of said element, a carriage a member fixed on said said base, means for supportsaid surface, measuring prising a movable part adapted to engage a surface or the slot in said work piece. and a device to indi means 101' moving said carriage comprising a rack mounted on said base. and a manually rotatable pinion meshing with said rack and mounted on said carriage.

WALTER 8. MG.

cate movement or said member, said REFERENCES I The following references are of record in the tile of this patent:

Buick Motor 00., Blue Print. Fixture to Check Lead 01 Splines, July 16. 1934, Tool and Drawing

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