US2658498A - Grinding wheel dressing mechanism - Google Patents

Description

Nov. 10, 1953 HOGLUND 2,658,498

GRINDING WHEEL DRESSING MECHANISM INVENTOR. NiLs H031, and

BY 4% J GRINDING WHEEL DRESSING MECHANISM 5 Sheets-Sheet 4 Filed Feb. 12, 1951 INVENTOR. Ni ls Ho ilund ATT NEY GRINDING WHEEL DRESSING MECHANISM 5 Sheets-Sheet 5 Filed Feb. 12, 1951 INVENTOR. Ni Ls Hoglund BY AT .RNfY

Patented Nov. 10, 1953 UNITED STATES PATENT OFFICE GRINDING WHEEL DRESSING MECHANISM Nils Hoglund, Union, N. J.

Application February 12, 1951, Serial No. 210,533

13 Claims.

My invention relates to grinding wheel dressing devices, more particularly to devices for dressing and forming grinding profiles on grinding wheels.

In one form of conventional dressing equipment where the contour of a templet is reproduced on the grinding surface of a grinding wheel on a reduced scale, a pantograph arrangement of complicated design is normally employed to transfer the contour from the templet to the surface of the wheel being dressed as the tool is moved across the surface of the grinding wheel. This usually involves the use of complicated link mechanism. Usually this older type of wheel dressing mechanism can be employed only on smaller grinding wheels used on saddle type machines.

Wheel dressing devices of conventional design are usually permanently fixed to the grinding equipment and are heavy and bulky. With the conventional dressing equipment it is diflicult to provide contours where sharp or undercut contours are required on the grinding wheel. It is also diflicult in devices available to dress to sharp angles and in some cases to dress more than a one-radius contour. Experienced operators are required to handle this type of equipment.

In conventional types of wheel dressing devices the grinding wheel cannot normally be dressed on the same side of the spindle as the grinding takes place. This causes wave marks in the grinding, resulting from eccentric distortion, the result of the center of gravity of the wheel not coinciding with the geometrical center line of the spindle. Further, in conventional types of dressers the wheel guards and coolant spouts normally have to be removed in order to expose the wheel so that the operator can dress the grinding wheel. This, of course, introduces hazards for which the guards are intended as protection.

Where the wheel dressing devices are permanently mounted on the grinding wheel apparatus, the positioning of the dresser, unless complicated supporting mechanism is provided, interferes with the full usage of the machine capacity and frequently re-alignments were necessary to assure accuracy of work.

A principal object of my invention, therefore, is to provide a simple and effective grinding wheel dressing and forming device of improved design.

Another object of my invention is to provide such a device which dispenses with the need for pantograph arrangement for producing on a reduced scale the contqur of a templet on a grinding wheel.

A further object of my invention is to provide a device of the kind described which can be easily and quickly moved from machine to machine and quickly set up without the necessity of redesigning the machine to accommodate the dresser.

A further object of my invention is to provide such a device in which the dressing tool can be manipulated to produce contours of small radius, or contours having sharp angles or are undercut, or have more than one radius.

A further object of my invention is to provide a device of the kind described which can be easily and effectively operated by an unskilled operator.

A further object of my invention is to provide a grinding wheel dressing mechanism which may be left on the grinder on the side of the work table or the magnetic chuck usually employed with the grinding apparatus without interferring with the grinding operation, thus saving the time required in removing and resetting the dresser during dressing operations.

A further object of my invention is to provide a device of the kind described which dresses the wheel on the same side of the spindle as that on which the grinding takes place, thereby eliminating wave marks in the resulting grinding.

A further object of my invention is to provide a wheel dressing mechanism which eliminates the need for removing wheel guards and coolant spouts during dressing operation.

A grinding wheel dressing apparatus made according to my invention includes a base having mounted thereon a pair of slides movable parallel to each other. One of the slides carries the dressing tool and the other slide carriers the cam for determining the shape of the contour on the dressing wheel. The two slides are interconnected by a. bell crank mechanism which cooperates with the cam surfaces on the two slides to determine a difierential movement of the slides in the same direction, such that the cam slide moves through a greater distance than the tooling slide during the same interval of time, thus reducing movement of the tool slide relative to the cam slide. Mounted on the tool slide for rotation about an axis normal to the movement of the slides is a lever mechanism pivoted closely adjacent one end of the lever mechanism. A diamond tool support is pivotally mounted at the shorter end so as to be mounted eccentrically of the axis of the rotation of the lever. oppositely disposed to the first lever is a second lever forming with the first a frame, the two levers supporting at their free ends remote from the tool support a cam follower which contacts the cam carried by the cam slide. The cam follower support, which is rotatably mounted at the free ends of the lever arms, is connected through a link mechanism to the rotatable tool support so that the tool support is made to follow the movement of the cam follower. lhe entire mechanism is normally held on the rinding wheel apparatus by a magnetic chuck, the tool coming into contact with the under side of the grinding wheel which contacts the work piece being ground so that the wheel is dressed from the same side and at the same point at which the grinding wheel accomplishes work on a work piece.

The invention will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a plan view of a grinding wheel dressing apparatus made according to my invention, Figure 2 is an end view of Figure 1, Figure 3 is a right-hand side elevation of Figure 1 and Figure 4 is a left-hand side elevation of Figure 1, Figure 5 is a perspective view of the apparatus shown in Figures 1 to 4 inclusive, Figure 6 is a section taken along the line 6--6 of Figure 1, Figure 7 is a View with portions removed showing details of construction of the slide support and bell crank cam follower and pusher associated therewith, Figure 8 is a perspective view with parts removed to show details of the slide and bell crank supports and Figure 9 shows details of the tool head support with its parts removed and in section to show details of construction.

General description Referring to the drawing and particularly to Figures 1, 2, 3, 4 and 8, a grinding wheel dressing apparatus made according to my invention comprises a base plate I8 having slidably mounted thereon a pair of slide assemblies laterally spaced from each other and movable parallel to each other upon the base. These slide assemblies comprise a tool supporting slide assembly shown generally at I2 and a templet supporting slide assembly shown generally at I3. These slides move toward and from the operator as viewed in Figure 1, the operator being positioned at the lower end of the figure so as to be able to grasp member in his right hand.

Mounted on the tool supporting slide assembly I2 is the tool and tool supporting head designated generally at It. The head is mounted for rotation about an axis eccentric to its main supporting shaft and normally to the slide movement in a manner to be described. A stylus or cam follower assembly designated generally at I5 is also mounted on the slide I2 and supported by levers or arms, in a manner to be described, from the same shaft as the tool supporting head. A link mechanism shown generally at I6 connects the stylus and the tool support to produce the desired movement of the tool as the stylus follows the cam I! mounted on the slide I3, the means for supporting the tool head and the stylus being so designed as to produce the desired ratio of movement of the tool with respect to the stylus to produce a reduced ratio of movement of the tool.

A cam follower and cam pusher of bell crank form shown generally at I8 and to be described in detail below is mounted for rotation on a vertical axis on housing support I I between the slides, and contacts cam surfaces to be described mounted on the slides to cause movement of the slides in the same direction but at a differential r t so that the templet slide moves a greater distance than the tool slide in the same interval of time to bring about a desired ratio of reduction of the movement of the tool slide relative to the cam movement.

Generally, in operation when the templet slide is moved manually back and forth in a direction parallel to the axis of the grinding wheel the bell crank causes movement of the tool slide in the same direction but at a reduced rate. This carries the forming tool transversely on the surface of the grinding wheel being dressed. Inasmuch as the tool and templet follower are mounted for rotation about an axis normal to the axis of the grinding wheel, the tool may be moved up and down with respect to the grinding wheel surface, and because the tool head is pivoted to rotate about a second axis relative to the first axis it can be rotated about its own axis to determine the degree of angle of contact with the wheel surface to follow sharp contours and the like.

Base and main frame assembly Referring particularly to Figures 1, 2, 6, 7 and I 8, it will be seen that the base I0 supports main 0nd slide guide 23 on which is mounted the slide 24 by means of ball bearing assembly 25 and 26. This second slide 23 in turn supports the cam I'I. Thus it will be seen that the slides 20 and 24 are mounted for movement parallel to each other. Formed between the slide guides I9 and 23 on the frame II is the bearing support 60, which supports the bell crank cam follower and pusher designated generally at I8 (see Figures 1, 7 and 8) and to be described in greater detail below.

Tool slide assembly Tool slide 20 is provided at one end with an end plate 21 overhanging the end of the slide and carrying a pair of spring guides 28 and 29, see Figures 1, 2, 4 and 6, supporting the springs 30 and 3|. These springs and spring guides are received within elongated chambers 32 and 33 in housing I I, the springs being compressed between the end walls of the chambers 32 and 33 and the end plate 21 to urge or bias the tool slide assembly back toward the operator as shown in Figure 1, the operator being positioned at the lower end of the figure so as to be able to grasp member 52 in his right hand.

Mounted on the slide 20 is a bearing housing 34 rotatably supporting a shaft 35, see Figures 1, 2, 6 and 9, to which are fixed the arms or levers 36 and 31. Arm 36 is attached to a hub 38 which has an offset portion 39 for pivotally supporting the tool supporting head 40 having the axially extending offset arm 4| for supporting the replaceable cutting or forming diamond tool 42 retained on the arm 4| by screws 43, see Figure 2. Tool supporting head 40 is mounted on stud or shaft 40' on an axis eccentric to shaft but parallel thereto for reasons to be explained. The cutting diamond 42 can rotate about its axis and the tool and head can rotate about the axis of shaft 35. The relationship of these elements is best shown in Figure 9.

Mounted on the free ends of the arms 36 and 31, which are locked to the shaft 35, is a rotatable shaft 44 to which is affixed an arm 45, see Figures 1, 4 and 5. Arm 45 carries a stylus or cam follower 46 which is replaceable and retained by screw 45. A lever 41 is fixed to the shaft 44 so that the shaft can be manually rotated to cause the stylus 46 to follow any portion of the templet surface of templet l7 and contact the templet normal to the surface to insure accurate contours on the grinding wheel being dressed.

In order to cause diamond cutting tool 42 to rotate in unison with the stylus a link mechanism comprising crank 48 is fixed to the shaft 44 and is connected to the arm or link 49 in turn connected with the arm 49' on tool head 48, see Figs. 1, 4 and 5.

A templet slide The templet slide 24' has vertically extending therefrom a web or supporting plate 5! to which the templet I! is secured. It is provided with a handle 52 for permitting the operator to manipulate the slide. As best shown in Figure 7 a spring 53 attached at one end to slide 24 and at H the other end to the frame, is placed under tension when the slide is moved toward the operator who stands in the position described above or down as in Figures 1 and 7. A plate 54 is mounted on the frame and extends beyond the frame to provide an undercover or dust protector for the underside of slide 24 and the bearings and 26 when the slide is extended over the far end of the frame. When the apparatus is in the position shown in Figure 1, protection is provided by a dust cover in the form of a flexible sheet 55, see Figures 3, 4 and 5, mounted on a retracting roller 56 mounted in the housing 51 at one end of the slide. Mounted in a slot or cavity 5'! in theslide is a cover plate 58 and ratio cam 59 to be discussed below.

Bell crank cam follower and pusher As shown in greater detail in Figure '7, the mechanism for transferring movement from the templet slide 24 to the tool slide 20 includes a bell crank cam follower and pusher 6| pivotally mounted, preferably in preloaded ball bearings on the bearing support 60 on frame II. It is provided with a pair of arms 62 and 63 at the ends of which are mounted vertical pins 64 and Pin 64 engages ratio cam 59 and serves as a cam follower, and pin 65 engages correcting cam St on tool slide 28. Springs and 3t urge the tool slide 20 against the pin 65 to turn crank d! counterclockwise. When cam slide 24 is moved forward, cam 59 pushing against pin 64, rotates the crank clockwise, the ratio of movement of the slide 29 to the movement of slide 24 being determined by the angle of the cam surface. Cam 56 on plate 2! acts as a correction element compensating for the shortening of the component length of the arm of the bell crank along a line parallel to the movement of slide 20. The shortening of the component length of the arm 62 brings pin 64 to a contact point on cam which is closer to the pivot point than that of the previous position, thus producing a smaller rotation of the bell crank cam than called for would, therefore, move the slide 29 a distance too small. The cam 56 counteracts this error as to distance between pin 65, and the pivot point becomes fore-shortened in the same amount perpendicular to the movements of the slides. Cam 65 causes slide 20 to move a greater distance than called for by movement of bell crank, thus compensating for the bell crank error. The ratio of movement of the two slides as pointed out above is determined directly by the angle of cam 69. The angle of this cam and also the correction 6 cam is the arctan of the ratio of the movements of the slides relative to the base. Due to the same direction movements of the two slides, the ratio of the movements of the two slides relative to each other has one unit number smaller than the ratio of movements relative to the base. For example, if the ratio of movements of the slides relative to each other should be 10 to 1, the ratio of the movements relative to the base will be 11 to 1. The same principle may be applied to other ratios.

Detailed operation Assuming the apparatus to be in the position shown in Figure 1 and in position to move across the surface of the grinding wheel, the operator grasps the handle 52 of the slide 24 with the right hand and the crank 41 with the left hand and moves the slide 24 away from him parallel to the axis of the wheel being dressed. As the slide 24 moves forward, cam 59 also moves forward and in contact with the pin 64, causing clockwise rotation of the bell crank 61. The arm 63 causes the pin 65 to move against cam surface 66, thereby also causing movement of the tool slide 20 in the same direction as the templet slide. As the templet slide moves forward the stylus or templet follower 46 moves along the contour surface ll of the templet IT. This causes a back and forth rotation of the arms 36 and 31 about the axis of the pin 35, causing up and down movement of the tool head 40. Since the tool head and stylus are interconnected through members 45, 44, 48 and 49, the tool head will be rotated about its own axis so that the cutting tool can assume relative to the surface of the grinding wheel the same position as the stylus assumes with respect to the contour surface of the templet but in reverse direction. Since the tool head is supported on a lever having a shorter length than that on which the stylus is supported, the movement of the diamond in a vertical direction is reduced in the ratio of the relative lengths of the two arms so that if arm 36 between the supporting pin 35 and the end of the stylus is ten units and the length of the offset portion 39 is one unit, the tool moves the distance in a vertical direction as does the stylus. Thus movement of the tool parallel to the grinding surface and in a radial direction relative to the axis of a grinding wheel will have a 10 to 1 reduction with reference to the cam surface.

Thus with an apparatus of the kind described high precision contour dressing is obtainedv The device is very simple to operate and may be used for all types of grinders. It is capable of dressing complex contours since the cutting tool can be controlled to a very fine degree. Because of its rugged construction and because it eliminates the usual pantograph arrangement, it is extremely accurate and maintains its accuracy over long periods of operation, since it eliminates the cause of adjustment difiiculties which result when complex linkage is utilized. This is because the mechanism comprises a simple ratio arm and ratio slide. The apparatus is compact, lightweight and simple in construction and requires less skill of the operator. Since it can be mounted at the end of a magnetic chuck normally utilized on grinding wheel apparatus, it allows full usage of machine capacity and redressing without making realignments necessary for accuracy checks. It is capable of being used without removing wheel guards, water spouts or other parts of the grinder and since it dresses the wheel from the same side as that on which the grinding takes place it eliminates the wave marks normally caused by eccentric distortion when the center of gravity of the grinding wheel does not coincide with the geometric center of the spindle. These and other advantages are obtained from a device of the kind made according to my invention.

I claim as my invention the following:

1. A wheel dressing apparatus comprising a base, a pair of laterally spaced slides mounted on said base and movable along parallel paths, a bell crank mechanism contacting said slides and positioned at the end of one of said slides and at the side of the other of said slides, said mechanism and slides having means to cause differential movement of said slides in the same direction, said means including a cam mounted on said other of said slides and contacting said bell crank, a tool support rotatably mounted on a pivot on said one of said slides and rotatable on an axis normal to the parallel paths of movement of said slides, said tool support comprising a lever mechanism having a tool at one end and a templet follower at the other end, and a templet on the other of said slides, said follower and templet contacting each other for determining movement of said tool when said slides are moved.

2. A wheel dressing apparatus comprising a base, a pair of laterally spaced slides mounted on said base and movable along parallel paths, a rotatable member mounted on a pivot on said base independently of said slides and contacting said slides and positioned at the end of one of said slides and at the side of the other of said slides, said rotatable member and slides having means to cause differential movement of said slides in the same direction, said means including a cam mounted on said other of said slides and contacting said rotatable member, a tool support rotatably mounted on a pivot on one of said slides and rotatable on an axis normal to the parallel paths of movement of said slides, said tool support having a tool and a templet follower mounted thereon, and a templet mounted on the other of said slides, said follower and templet contacting each other for determining movement of said tool when said slides are moved.

3. A grinding wheel dressing apparatus including a base, a pair of slides movable parallel to each other on said base, one of said slides supporting a tool and templet follower and the other of said slides supporting a templet in contact with said follower, a pivoted cam follower and cam pusher mounted on said base between said slides, one of said slides having a cam contacted by said cam follower and pusher whereby movement of said one slide causes rotation of the cam follower to move the other slide in the same direction, said cam follower and pusher and said cam providing differential movement of said slides, said cam having an elongated triangular shape whereby movement of said one slide will cause angular movement of the cam follower and pusher causing a smaller movement of the other slide.

4. A grinding wheel dressing apparatus including a base, a pair of slides movable parallel to each other on said base, one of said slides supporting a tool and templet follower and the other of said slides supporting a templet in contact with said follower, a pivoted cam follower and cam pusher mounted on said base between said slides, each of said slides having a cam surface contacted by said cam follower and pusher whereby movement of one slide causes rotation of the cam follower to move the other slide in the same direction, said cam follower and pusher and said cams causing differential movement of said slides, said cam on one of said slides having an elongated triangular shape and the cam on the other of said slides having a surface formed at an angle to the line of movement of said slides whereby movement of the one slide will cause angular movement of the cam follower and pusher resulting in a smaller movement of the other slide.

5. A grinding wheel dressing apparatus including a base, a pair of slides movable parallel to each other on said base, a rotatable cam follower and cam pusher mounted on said base adjacent the end of one of said slides and at the side of the other of said slides, each of said slides having a cam surface contacted by said cam follower and pusher whereby movement of one slide causes rotation of the cam follower to move the other slide in the same direction, said cam follower and pusher and said cams providing differential movement of said slides, said cam on the other of said slides having an elongated triangular shape and the cam on said one slide having a surface at an angle to the line of movement of said slides whereby a movement of said other slide will cause a rotation of the cam follower and pusher causing a smaller movement of said one slide, a tool and templet follower being supported on one of said slides and a templet on the other of said slides, said templet follower and templet being in contact with each other.

6. A grinding wheel dressing apparatus including a base, a pair of slides movable along parallel paths on said base, a rotatable cam follower and cam pusher mounted on a pivot on said base between said slides having a pair of pins thereon, said cam follower and cam pusher being positioned adjacent the end of one of said slides and at the side of the other slide, each of said slides having a cam surface contacted by one of the pins on said cam follower and pusher whereby movement of one slide causes rotation of the cam follower and pusher to move said second slide in the same direction, said cam follower and pusher and said cams providing differential movement of said slides, the cam on the other of said slides having an elongated triangular shape and the cam on said one slide having a surface at an angle to the line of movement of said slides whereby a long movement of said other slide will cause a rotation of the cam follower and pusher causing a smaller movement of said one slide.

'7. A wheel dressing apparatus comprising a base, a pair of laterally spaced slide mounted for parallel movement on said base, one of said slides including a bearing housing and having an overhanging end plate at the other end thereof, said base having a pair of cavities therein and springs mounted under compression within said cavities and in contact with said base and said end plate for urging said slide in one direction, a shaft rotatably mounted in said bearing housing, a lever mechanism mounted for rotation on said shaft, said shaft having an axis normal to the path of movement of said slides and having an offset portion at one end thereof, a tool head mounted on said offset portion for rotation on an axis parallel to the axis of rotation.

9 of d le er and. ha ing a po ion e tend ng non mally to sa d le e a dre sing to l m unted at h free end i sa d portion, a d mean on: ct d to said ever mechanism or rota in said lever anism abou said haf and sa d tool support and tool about its axis, and means in cluding a o at le memb r co a t n sa d lide for ausin mov men of said id s n the ame direction, a templet follower mounted on said lever mechanism, a templet mounted on the other slide, said templet and follower contacting each other to control movement of said tool.

8; A wheel dressing apparatus having a base, a main frame housing mounted thereon, a pair of slide guides mounted on said housing and laterally spaced from each other and lying parallel to each o her, aid housin h ving a bearing sup.- n rt, a p ir of slides mounted on said slide guides and a bell era-n1; cam follow r and pusher rotate ably mounted on said bearing support, said bell crank being mounted at the end of one of said slides and at one side of the other of said slides, ams mo ted on s des, said, cam follow and pusher having elements in contact with said cam whereby movement of one slide will cause movement of the other slide, and resilient means contacting one of said slides for urging one of said slides into contact with said bell crank, a bearing housing mounted on one of said slides and a pair of lever arms fixed to each other at one end and rotatably supported on said bearin housing to rotate about an axis normal to the movement of said slides, one of said lever arms having an oifset portion rotatably supporting a tool supporting head at the end thereof, a second rotatable shaft mounted at the other end of said lever arms, one end of said shaft rotatably supporting a templet follower, and a crank attached to the other end and a link connected between said crank and said tool supporting head, a templet mounted on the other slide, said templet follower contacting said templet, said templet being mounted in a vertical position on said templet slide, a retracting roller mounted on one end of said templet slide and a flexible elongated cover member secured thereto and to said base and in a position to cover the underside of said templet slide to provide a dust cover therefor.

9. A grinding wheel dressing apparatus having a base, a pair of slide guides mounted on said base and laterally spaced from each other and lying parallel to each other, said base having a bearing support, a pair of slides mounted on said slide guides and a rotatable cam follower and pusher rotatably mounted on said bearing support, said cam follower and pusher being positioned at the end of one of said slides and at the side of the other of said slides, a cam mounted on said other slide, said cam follower and pusher having elements in contact with said cam and said first slide whereby movement of one slide will cause movement of the other slide, resilient means contacting one of said slides for urging said one slide in contact with said rotatable cam follower and pusher, a bearin housing mounted on said one slide and a pair of spaced lever arms fixed to each other at one end and rotatably supported on said bearing housing to rotate about an axi normal to the movement of said slides, one of said arms having a portion rotatably supporting a tool supporting head, a second shaft rotatably mounted at the other ends of said lever arms, one end of said shaft supporting a templet follower and the other being connected to said tool supporting head by a link mechanism, a templet mounted on e rli e. s i oll nnn antin sai ism: nls in ntr m re nent 9 said tool supportin head.

A h e dressing app tus h vin a base. a main frame housing mounted thereon, a pair of Slide u s moun ed n a d hous n and e ll pa fr m nbh ther and l i pa alle to 9 oth a h u n hav ng 2 .34 ns su rt, a Pa r o s ides innnntsd on said de u de nd n bell c an ol o an pusher r t bl mou ed n d bea in n": face, Said ll be n moun d at th end one of s d id s a d a he side oi t the of sa d s d s, a ra n a n mount d n sa the lid and a emen in sam o sai n of said Slides, id m fellows and pu her ha g elem nts n n n nt it id: 3 W Whe es-v 29??? ment of one slid will cause movement of the other slide, said frame housing having cavities ere nd p in ans in d ca iti s. and in ontact With said onesl'ide for urging said one ud i c ntact it sa d ollower and pu her, a bearing housing mounted on aid tool slide and a pair of lever arms fixed to each other at one end and rotatably supported on said bearing housing on an axis normal to the movement of said slides, one of said lever arms rotatably supporting a tool supporting head, a second shaft rotatably mounted at the other ends of said lever arms, one end of said shaft rotatably supporting a templet follower and the other end being connected by a link mechanism to said tool supporting head, a templet mounted on the other slide, said templet follower contacting said templet.

11. A wheel dressing apparatus having a base, a pair of slide guides mounted on said base and laterally spaced from each other and lying par allel to each other, said base having a bearing support, a pair of slides mounted on said slide guides and a rotatable cam follower and pusher rotatably mounted on said bearing support, said cam follower and pusher being mounted on the end of one of said slides and at the side of the other of said slides, an elongated triangularly shaped cam supported at the side of the other slide in a plane parallel to said base, a correcting cam mounted on said one slide, said cam follower and pusher having elements in contact with said cams whereby movement of one slide will cause movement of the other slide, lever mechanism rotatably supported on said one slide to rotate about an axis normal to the movement of said slides, said lever mechanism rotatably supporting a tool supporting head at the end thereof, a second shaft rotatably mounted on said lever mechanism, one end of said shaft rotatably supporting a templet follower and the other being connected to said tool supporting head, a templet mounted on said other slide in a plane normal to the plane of said triangularly shaped cam, said templet follower contacting said templet.

12. A wheel dressing apparatus having a base, a pair of slide guides mounted on said base and laterally spaced from each other and lying parallel to each other, one of said slide guides being shorter than the other, said base having a bearing support, a pair of slides mounted on said slide guides and a rotatable cam follower and pusher rotatably mounted on said bearing support, said follower and pusher being positioned at the end of said shorter slide guide and at the side of the other of said slide guides, cams mounted on said slides, the cam on the slide on the longer slide guide being of elongated triangular rectangular shape, said follower and pusher having elements in contact with said cams whereby movement of the slide on the longer slide guide 'will cause movement of the other slide, resilient means contacting one of said slides for urging one of said slides into contact with said follower and pusher, a rotatable lever mounted on said other slide and a rotatably supported templet follower mounted on said lever, a link connection between said templet follower and said tool supporting head, a templet mounted on the slide on the longer slide guide, said templet follower contacting said templet, movement of the slide on the longer slide guide causing a lesser movement of said other slide.

13. A wheel dressing apparatus comprising a base, a pair of spaced slides mounted on said base and movable relative to each other along spaced parallel paths, a rotatable bell crank mechanism mounted on a pivot having an axis between said paths and contacting said slides, said rotatable mechanism and slides having means to cause differential movement of said slides in the same direction, a tool support rotatably mounted on a pivot on one of said slides and rotatable during operation of said apparatus on an axis normal to the parallel paths or move ment of said slides, said tool support comprising a lever mechanism and having a tool at one end and a templet follower at the other end, said lever mechanism being rotatable about on a pivot having an axis normal to the path of said slides and a templet on the other of said slides, said follower and templet contacting each other for determining movement of said tool when said slides are moved.

NILS HOGLUND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,313,543 Keller Aug. 19, 1919 2,467,020 Fischer Apr. 12, 1949 2,469,844 Porter May 10, 1949 FOREIGN PATENTS Number Country Date 66,064 Germany Dec. 12, 1892

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