US3037329A

US3037329A - Method and apparatus for grinding drills

Info

Publication number: US3037329A
Application number: US685212A
Authority: US
Inventors: Ernst Hans; William A Haggerty; Eugene L Ritter
Original assignee: Cincinnati Milling Machine Co
Current assignee: Milacron Inc
Priority date: 1957-09-20
Filing date: 1957-09-20
Publication date: 1962-06-05
Anticipated expiration: 1979-06-05
Also published as: DE1284320B

Description

June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 11 Sheets-Sheet 1 INVENTO RS HANS ERNST WILLIAM A.HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 11 Sheets-Sheet 2 ATTORNEYS June 5, 1962 H. ERNST ETAL METHOD AND APPARATUS FOR GRINDING DRILLS l1 Sheets-Sheet 3 INVENTORS HANS ERNST WILLIAM A.HAG

Filed Sept. 20, 1957 GERTY EUGENE L. RITTER BY r/YT/Cu'Q-M- ATTORNEYS June 5, 1962 H. ERNST ETAL 3,

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 ll Sheets-Sheet 4 lNVENTORS HANS ERNST WILLIAM A.HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H. ERNST ETAL METHOD AND APPARATUS FOR GRINDING DRILLS l1 Sheets-Sheet 5 Filed Sept. 20, 1957 Raw Ill m n INVENTORS HANS ERNST WILLIAM A.HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 ll Sheets-Sheet 6 A30 /2a /53 I52 /29 5a /5/ J /2/ ///a //7 //6' //.9 [/5 I47 9 M4 g5 fl 141g. 9-

WILLIAM A. HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H. ERNST ETAL METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 ll Sheets-Sheet 7 WILLIAM A.HAGGERTY EUGEN E L.R|TTER ATTORNEYS June 5, 1962 H. ERNST ETAL METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 ll Sheets-Sheet 8 Q wmw Nu N m mmN INVENTORS HANS ERNST WILLIAM A.HAGGERTY EUGENE L.RlTTER riff/dam AT TO RNEYS June 5, 1962 H'. ERNST ETAL METHOD AND APPARATUS FOR GRINDING DRILLS l1 Sheets-Sheet 9 Filed Sept. 20, 1957 INVENTORS HANS ERNST ILLIAM A. HAGGERTY EUGENE L. RITTER ATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

' METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 ll Sheets-Sheet 10 INVENTORS HANS ERNST [8 WILLIAM A.HAGGERTY EUGENE L.RITTER BY ,mzwwf wv ATTORNEYS June 5, 1962 H. ERNST ETAL 3,037,329

METHOD AND APPARATUS FOR GRINDING DRILLS Filed Sept. 20, 1957 ll SheetsSheet 11 4 m z; m T(?; N

INVENTORS HANS ERNST N Q q) WILLIAM A.HAGGERTY EUGENE L.R|TTER AT TORNEYS atenr- 3,037,329 Patented June 5, 1962 thee 3,037,329 METHOD AND APPARATUS FUR GRINDING DRILLS;

Hans Ernst, William A. Haggerty, and Eugene L. Ritter, all of Cincinnati, Ohio, assignors to The Eincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Filed Sept. 20, 1957, Ser. No. 685,212 22 Claims. (Cl. 51-43) This invention relates to a new and improved method and apparatus for grinding metal Working drills.

The method and apparatus of this invention is directed more particularly to the manufacture of the improved type of drill shown in co-pending application Serial No. 566,504, filed February 20, 1956, in the United States Patent Office, now Ptaent No. 2,903,922, dated September 15, 1959.

It is desirable in metal working drills that the tip end of the drill should act as a pilot means for centering the drill at the spot where the hole is to be drilled, but conventional drills are unsatisfactory in this respect in that they have chisel edge at the tip which is ineffective for centering and pilot purposes because it is a straight line edge perpendicular to the axis of the drill. A more satisfactory drill would be one having some form of selfcentering pilot means at the tip of the drill, but it also must be such that it can be generated as part of the grinding process of sharpening the main cutting edges on the drill and thus not require a separate operation.

Shapes might be conceived or designed for the end of a drill which could not be generated in a single generative grinding cycle, and since it is preferable to utilize a grinding wheel for the sharpening process, the problem of generation with a revolving body such as a rotatable grinding wheel becomes involved and sets up design limitations.

This invention, therefore, deals with a new and improved process and apparatus for not only generating the new and improved form of pilot means on the drill shown in the co-pending application, but. a method and apparatus which is so contrived that the entire end of the drill including the pilot means and cutting edges may be ground in a continuous generative grinding operation automatically, the arrangement being such that the generative cycle repeats automatically for each main cutting edge to be ground or sharpened.

One of the objects of this invention is to provide a new and improved method of generatively grinding the end of a metal working drill to produce a drill having improved centering and cutting characteristics.

Another object of this invention is to provide a new and improved apparatus for performing the method of this invention.

A further object of this invention is to provide a new and improved method of the character described which will produce a new and improved tip on a drill and one which can be generated in the same cycle with the generation or grinding of the main cutting edges on the end of the drill.

Another object of this inventionis to provide a new and improved method of the character described in which a rotatable grinding Wheel may be utilized as the generating agent.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described. with- 2 in the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

FIGURE 1 is a view in elevation of a machine em-. bodying the principles of this invention.

FIGURE 2 is a plan section on the line 2-2- of FIG- URE 1.

FIGURE 3 is a section on the line 3-3 of FIGURE 1.

FIGURE 4 is a vertical section on the line 4-4 of FIGURE 1 showing the lever mechanism for shifting the tool carriage laterally.

FIGURE 5 is a detail section on the line 5-5' of FIG- URE 12.

FIGURE 6 is a section on the line 66 of FIG- URE 4.

FIGURE 7 is a View on the line 77 of FIGURE 6.

FIGURE 8 is a plan view on the line 88 of FIG- URE 1.

FIGURE 9 is a sectional view on the line 9-9 of FIGURE 8.

FIGURE 10 is a section through the work holder taken on the line 1i10 of FIGURE 1.

FIGURE 11 is a plan view of the work holder on the line 11-11 of FIGURE 10.

FIGURE 12 is a detail section taken on the line 1212 of FIGURE 1.

FIGURE 13 is a detail section on the line 1313 of FIGURE 11.

FIGURE 14 is a detail section on the line 14-14 of FIGURE 13.

FIGURE 15 is a view of one of the lateral control cams of the machine as viewed on the line 1515 of FIGURE 1.

FIGURE 16 is a section on the line 1616 of FIG- URE 15.

FIGURE 17 is a diagram of the position of the grinding wheel in its cycle of movement related to a fixed position of the drill.

FIGURES 18, 19, and 20 show difierent instantaneous positions of the grinding wheel as it moves through its cycle about the drill.

FIGURES 21, 22, and 23 show diiferent arrangements of the drill with respect to a grinding element.

The method and machine of this invention is designed for manufacturing the ends of drills, such as metal working drills, to provide a new and improved cutting face thereon, and may be utilized either initially to form a cutting face on the end of drill blanks, or for refinishing and resharpening the cutting edges thereon. This method and machine are designed more particularly for pointing drills of the type disclosed in U.S. Patent No. 2,903,922.

Since the entire end surface of a drill including the cutting edges or lips is that portion of the drill that does the cutting, the entire end surface of the drill may be conveniently termed herein as the cutting face of the drill.

In general, the method of this invention includes the steps of positioning the axis of a drill in a plane containing the axis of a grinding wheel, and at a suitable angle to the working face of the grinding wheel or the like, and then effecting a three dimensional relative movement between said faces in a substantially conical spiral path.

This can be accomplished in various ways. For instance, as shown in FIGURE 21, a conical shaped grinding wheel 25 may be utilized, and the drill axis 26 maybe arranged in a radial plane of the wheel that contains its axis 27 and at an acute angle to the working face thereof: or the drill axis 26 may be arranged perpendicular to the axis 27 of the wheel 25 and at an acute angle to the working face thereof as shown in FIGURE 22. Again, the axis of the drill 2 6 may be positioned at an acute angle to the working face of a cylindrical grinding wheel 28 while lying in a radial plane through its axis 27 as shown in FIGURE 23. In each case the axis of the drill lies in a radial plane containing the axis of the grinding wheel and at an angle to the working or grinding face thereof, it being understood that this angle will vary in accordance with the point angle of the drill.

The line of intersection of the radial plane with the periphery of the wheel is indicated as AB in these figures and constitutes one of the generative line elements in the surface of the wheel, and this line element terminates at a corner of the wheel which is provided preferably with a small radius as shown at B. At this corner, the line element meets a reference axis GG at an angle. The reference axis is always parallel to the drill axis.

Neglecting rotation of the grinding Wheel, it will be obvious that by sweeping the active line element such as AB over the surface of the drill in a properly guided movement, a desired shape of surface can be produced or generated. Of course, the same effect would be produced if the drill surface were moved instead of the line.

When it is selected that the grinding wheel do the sweeping, the reference axis GG is utilized as the axis of gyration of the grinding Wheel, whereas when the drill does the moving about the wheel, the axis of the grinding wheel becomes the axis of gyration or rotation. If the grinding wheel axis is fixed, and the drill rotated, the axis of the drill becomes the axis of gyration. It will thus be seen that in the generating process either the grinding wheel axis or the drill axis may be held stationary while the other is moved; or part of the movements may be applied to one and the remaining movement to the other. Herein the active line element of a rotating grinding wheel is considered to be the one that is instantaneously tangent to the surface being ground.

Having properly positioned the parts in accordance with the first step, the three dimensional generative movement is performed by moving one face bodily relative to the other such as relatively moving one of the parts toward the other, as indicated by the arrow F in these figures, and simultaneously effecting a second movement laterally of the first movement in the direction of the arrow L which produces a resultant movement generally along and parallel to the active generative line element A-B. If the grinding wheel does the moving, then the direction of the arrows is reversed.

In addition to this compound movement, a circular or gyrating motion is simultaneously effected between wheel and drill in order to sweep the generatrix over the end surface of the drill and thereby effect a three dimensional grinding operation. The last-named motion is effected about a gyratory axis by moving the wheel about the drill, the drill about the wheel, or simply rotating the drill itself about its own axis. The compound linear movement and the gyratory motion are effected simultaneously with the result that a conical spiral cutting path is generated, and this action is repeated for each lip to be ground on the drill.

Thus, the method consists of positioning the axis of the drill in a radial plane of a grinding wheel, with the drill axis at a suitable angle to a line element in the surface of the wheel lying in said plane, effecting relative movement between the drill face and the grinding wheel face along normally related lines, one of which is the axis of the drill, and simultaneously effecting a gyratory movement of one of the members about a gyratory axis lying in said radial plane of the grinding wheel and parallel to the drill axis.

The generating cycle for grinding each lip must be started in proper relation to the lip to be ground in order 4 to grind part of the tip portion before grinding the lip portion.

This is done by theoretically positioning the active line element of the grinding wheel substantially midway of the flute. At the same time, the active line element AB overlies the center of the drill, as shown in FIGURE 18. Thus, as the active line element sweeps over the flute portion toward the lip only the tip portion will be ground.

As the rotation continues and the lateral movement L continues, the grinding wheel will clear the tip which is necessary so that the continued axial movement necessary to grind the lip will not grind off the tip, but leave it upstanding. After a predetermined rotation sufficient to grind the lip portion the parts are separated and repositioned for grinding the next lip.

Although the machine or apparatus for carrying out the principles of this invention will vary in accordance with the arrangement of the parts, some of which are shown in FIGURES 21, 22, and 23, the machine will still conform to the method disclosed. It will, therefore, be simpler to explain this invention by selecting one of the arrangements illustrating the method. To this end, the invention will be described, utilizing the arrangement shown in FIGURE 21 and imparting all the motions to the grinding wheel to produce a conical spiral or three-dimensional spiral cutting path. For simplicity, it will also be explained in connection with a two-lip twist drill, but it will be understood that the same principles will apply to drills having more than two flutes, because the method or generating cycle is merely repeated for each lip to be ground.

In FIGURES 18, 19, and 20 are views showing the grinding of a twist drill 29 in accordance with this invention. In these views, the axis of the drill and the grinding wheel are parallel in accordance with the arrangement shown in FIGURE 21. The axis of gyration of the grinding wheel is indicated at G--G. The machine construction is such that it provides such an axis to which all the movements described herein are imparted, and so in these FIGURES 17, 18, 19 and 20, it can be considered that this axis moves relative to the drill for ease of understanding. It will be obvious that the first contact of the drill by the wheel will be the highest point axially on the cutting face of the drill as shown in FIG- URE 18 because the Wheel then moves on and axially into the drill as shown in FIGURES 19 and 20. Therefore, it is necessary to select a starting line on the cutting face of the drill which represents the highest point to be ground, and to insure that the wheel is so positioned in its orbit about the drill that the wheel will first contact this line as it starts to grind. For the purposes of this explanation the drill is held stationary and clamped in a fixture in the machine. Thus, all motions are imparted to the grinding wheel and its axis of gyration. In FIGURE 17 are shown some of the positions of the grinding wheel as it moves about the drill in its gyratory path, and FIGURES l8, l9, and 20 illustrate instantaneous positions of the grinding wheel in this path.

Considering FIGURES 17 and 18 together, FIGURE 18 shows the grinding wheel just touching the drill and thus just starting to grind. In FIGURE 17 the corresponding position of the grinding wheel 25 is indicated by the position Mia- 18a. The line 30 represents the position of the active line element AB on the grinding wheel, and it will be noted that it overlies the midportion of the flute 40 of the drill. The grinding wheel then moves clockwise in its orbit to the position 19a19a shown in FIGURE 17, and simultaneously in an axial direction as indicated by the arrow 31 in FIGURE 18 and laterally in the direction indicated by the arrow 32 in FIGURE 18, which puts the grinding wheel in the position shown in FIGURE 19.

The wheel continues in its orbit to the position 20a- 20a in FIGURE 17 while simultaneously continuing its,

axial and lateral movements in the same directions which puts the wheel in the position shown in FIGURE 20. This completes the grinding of the area 33 between the cutting lip 34 and the arcuate rim 35 of the next flute 36. The same cycle is repeated for grinding the area 37 between the next cutting lip 38 and the arcuate rim 39 of the next flute 40.

However, before repeating the cycle to grind'the area 37, it is necessary to retract the grinding wheel quickly and shift it laterally and axially in a reverse direction as it continues in its orbital movement until it is in the same relative position with respect to the drill as shown in FIGURE 18 but displaced 180 degrees therefrom. The grinding will now start on the line 41, shown in FIGURE 17. The grinding wheel is now in the position 18b- 1'8b and continues to position 19b19b and finally finishes grinding when in the position 2tlb-2hb. A second retractive movement is now quickly efiected as the grinding wheel completes its orbit back to the starting position I'Sa-lSa.

It will now be noted in FIGURE 17 that the center lines 26a and 26b cross at the center on axis 26 of the drill and that in reality the gyratory axis G travels back and forth along the center line 26a from G1 to G2 even though perpendicular to it. Thus, while the axis G is moving away from the center of the drill along the center line 26a, one lip is being automatically ground, it being remembered that an axial movement perpendicular to the drawing is also taking place simultaneously. At the end of grinding, the axis G is quickly repositioned to the other side of the drill center, and the next lip is ground. Thus, in one complete circle, each lip is ground in an automatic cycle, and the automatic cycle automatically repeats itself. Means are provided for independently feeding the drill axially toward the grinding wheel to take off as much stock as is necessary to properly grind and sharpen the drill.

A good embodiment of a machine for carrying out the process of this invention will now be described. Referring to FIGURE 2, a conical-shaped grinding wheel 25, is suitably mounted in a chuck 50 which is secured to the end of a spindle 51. The spindle is supported by anti-friction bearings 52 in a carrier 53. The rear end of the spindle 51 is provided with a drive pinion 54 which intermeshes with an internal gear 55. The carrier 53 is supported for rotation by suitable anti-friction bearings 56 in a support 57. Attention is invited to the fact that the spindle 51 is eccentrically mounted in the carrier 53 by an amount indicated by the distance 53 in FIGURE 2, which is preferably equal to the radius of the grinding wheel 25 and indicated by the reference numeral 59. It will now be seen that the periphery of the grinding wheel always passes through the axis 64 of rotation of the carrier 53, and this axis corresponds to the reference axis G-G.

The carrier has integrally connected therewith a drive gear 60 which meshes with a drive pinion 61 mounted on the end of a shaft 62, the shaft being anti-frictionally journaled at 63 in the support 57. It will now be apparent that if the support 57 was held stationary and the carrier 53 rotated, it would move the grinding wheel 25 bodily in a circle about the axis of rotation 64 of the carrier, and throughout this rotation the periphery of the grinding wheel 25 would always pass through or be tangent to the axis 64.

As shown in FIGURE 2, the drill 29 is mounted in a fixture, indicated generally by the reference numeral 65, so that the axis 26 of the drill is parallel to the axis of rotation 67- of the spindle 51 and grinding wheel 25. It will thus be seen that if the axis of rotation 64 of the carrier 53 is aligned withthe axis 26 of the drill that rotation of the carrier will move the grinding wheel 25 in an orbit about the axis of the drill, and in this case the orbit would be a circle.

Since all movements are to be imparted to the grinding wheel in this construction, the grinding wheel must be capable of axial movements as well as lateral movements, and therefore the support 57 is, in turn, mounted for two directional movement at right angles to each other.

As shown in FIGURE 4, the support 57 is provided with depending lugs or bosses, one of which is indicated by the reference numeral 63 located at one side of the axis of rotation 64 of the carrier, and two of which are located on the other side of the axis and indicated by the reference numerals 69 and 70 as shown in FIG- URE 3. It will be noted that the bosses form a threepoint support for the member 57. The boss 68 has a bore 71 through which passes a supporting rod or guide 72 that is anchored in a sub-support 73. Likewise, the bosses 69 and 70 have suitably formed bores by which they are supported on a guide rod 74 which is also anchored in the sub-support 73. It will be noted that there is sufiicient clearance between the bosses and the subsupport to permit longitudinal sliding movement of the member 57 and a spring 75 is interposed between the boss 70 and acollar 76 which is pinned at 77 to the rod 74. The spring 75 exerts a constant urge in a direction to axially retract the grinding wheel 25 from the drill 29 as shown in FIGURE 2.

The sub-support 73 also has three bosses, 78, 79, and 80, in which are formed suitable bores so that the bosses 78 and 79 are slidably mounted on a guide rod 81, and the boss 80 is guided on a guide rod 82. The guide rods 81 and 82 are suitably anchored in the bed 83 of the machine. A spring 84 is interposed between the boss 78 and a collar 85 suitably secured as by a pin 86 to the guide rod 31 whereby the spring 84 continuously urges the sub-support 73 and grinding wheel carried thereby away from the axis of. the drill 29 in a horizontal plane as viewed in FIGURE 2. It will now be seen that the grinding wheel 25 is supported for three different movements, i.e., a planetary movement about the drill 29 by virtue of the rotary carrier 53, an axial movement and a lateral movement with respect to the drill 29 by virtue of the two-directional slidable support 57.

The power drive mechanism for rotating the carrier 53 and the grinding wheel '25 is shown in FIGURE 2 and comprises a motor 87 which is supported on the movable frame 57, and has a drive shaft 88 which is coupled to a shaft 89 anti-trictionally mounted in the frame 57. The shaft 89 carries a pinion 90 which meshes with a gear 91. The gear 91 forms part of reduction gearing shown in FIGURE 4 in which it will be seen that the gear 91 is supported on a stub shaft 92 which also carries a gear 93 integral with the gear 9 1 and in mesh with a large gear 94 which is supported for free rotation on shaft 62 as shown in FIGURE 2.

The gear 94 is connected by clutch teeth 95 to a shiftable clutch member 96 which is keyed at 97 to the shaft 62. A spring 98 is interposed between the clutch member 96 and a flange 99 secured to the shaft 62 for maintaining the clutch member in driving engagement with the gear 94. The clutch member 96 may be disengaged by a clutch shifter fork 100. The shaft 89 also has directly secured thereto the internal gear 55, which is the drive gear for the grinding wheel, whereby it will be seen that the motor 87 drives directly through the shaft '89 to the internal gear 55 to effect high speed rotation of the grinding wheel, but drives through the

reduction gearing

91, 93, and 94 to the pinion 61 to effect a relatively slow rotation to the carrier 53.

The rear end ofthe carrier 53 has a cam member 101 secured thereto as by screws 102, and it will be noted from FIGURE 3 that the spring 75 is effective to urge the cam member 101 toward the right as viewed in FIG- URE 2 and that the spring 84 is effective to urge the cam member 101 toward the bottom of the drawing as shown in FIGURE 2. The axial movement of the carrier 53 is opposed by a cam roller 103 which rides in engagement with a cam surface 104 formed on the memher 101. The lateral movement of the carrier 53 is opposed by a cam follower 105 which rides in engagement with a peripheral earn surface 106 formed on the member 101. Attention is invited to the fact that the

cam rollers

103 and 105 are held stationary during the operation of the machine, and, therefore, as viewed in FIGURE 2, any rise in the cam surface 104 will cause axial movement of the grinding wheel 25 toward the drill 29 and that any rise in the cam surface 106 will cause movement of the grinding wheel 25 laterally of the axis of the drill. The cam roller 105 is rotatably supported on the end of a lever arm 136 which is pivotally supported on a pin 107 located in the support 57 as shown in FIG- URE 4.

The lever arm 136 has a fulcrum surface 108 which engages with an adjustable fulcrum roller 109. The roller 109 is mounted in a bracket, indicated generally by the reference numeral 110, said bracket being guided at 111 and 112 on a vertical guide rod 113 which is anchored in the bed of the machine.

The bracket 110, as shown in FIGURE 1, has a lateral extension 114 which, as shown in FIGURE 9, has a threaded hole 115 in which is threaded a vertical adjusting screw 116. The screw 116 extends through the top of the fixed housing 117 of the machine and has a reduced portion 118 upon which is mounted a flange bushing 119. The bushing is held in position by a circular plate 120 which is fastened to the top of the housing as by screws 121. The reduced portion 118 also has an axially serrated portion 122 in the form of fine gear teeth upon which is slidably mounted a pinion gear 123, which has an elongated hub that abuts against the end of a rotator 124 which is also mounted on the reduced end 118. A cap screw 125 is threaded in the end of the screw 116 and overlaps the rotator 124 to hold the parts in position on the screw 116. The rotator 124 has a manually operable handle 126. When the rotator 124 is moved by the handle 126, the gear 123 is rotated, and through idler gear 127 (FIG. 8), rotates the coupled gears 128 and 129 mounted on a pin 130 which is fixed in the plate 120. The gear 129 intermeshes with a large internal gear 131 formed on the inside of a dial plate 132. It will be seen that the gearing arrangement forms a reduction in the drive between the screw 116 and the plate 132 whereby a large number of revolutions must be imparted to the screw in order to effect one rotation of the dial 132. In fact, the reduction is suflicient that the screw 116 may be rotated the necessary number of times to move the fulcrum roller 109 through its complete range of travel while only effecting one revolution of the dial plate 132. This adjusting mechanism is for the purpose of varying the throw effected by the cam 106 in moving the grinding wheel laterally, and the lateral movement is adjusted in accordance with the diameter of the drill being ground. Therefore, the setting for different diameters of drills may be indicated by placing the drill diameter sizes sequentially in the boxes 133 on the side of the indicator plate 132 as shown in FIGURE 8.

As viewed in FIGURE 4, the action of the fulcrum mechanism will be better understood if it is remembered that the spring 84 shown in FIGURE 3 is continuously acting on the slide 57 to push the pin 107 and the cam 106 against opposite ends of the lever 136, and this action is resisted by the fixed roller 109. Therefore, when a rise on the cam 106 engages the roller 105 and tends to move it toward the right, as viewed in FIG- URE 4, it will pivot the lever 136 about the roller 109 and move the pin 107 to the left and thereby move the slide 57. Shifting of the fulcrum 109 really changes the length of the lever arm 134 with respect to the lever arm 135 which is substantially a constant distance. There fore, by lengthening or shortening the lever arm 134 the lateral movement of the slide 57 may be adjusted for a given rise on the cam. Since the cam 106 makes a full revolution, regardless of the diameter of the drill,

if the lateral movement of the grinding wheel is changed, the axial movement of the grinding wheel should correspondingly be changed. Therefore, the roller 103 shown in FIGURES l and 2 which acts on the cam 104 is similarly supported on a fulcrum mechanism.

As shown in FIGURE 1, the roller 103 is mounted on the end of a fulcrum lever 136' which is mounted on a pivot pin 137 carried by the support 57, and the lever 136 has a fulcrum surface 138 which bears against a fulcrum roller 139. The fulcrum roller 139 is rotatably mounted in a vertically movable bracket 140 which is threaded on a screw 141. The bracket 140 has a wing 141' (FIG. 2) integral therewith in which is formed a groove 142 for receiving a pin 143 carried by the bracket 110. This prevents rotation of the bracket 140 relative to the screw 141. The screw 141, as shown in FIGURE 9, has a flange 144 and a spaced threaded collar 145 threaded thereon by means of which it is supported in a bore 146 formed in the member 114, whereby when the extension 114 is vertically adjusted by the screw 116, the screw 141 will also be vertically adjusted in the same proportion. Attention is invited to the fact that the fulcrum adjustment of the lever 136' is for the purpose of changing the axial movement of the grinding wheel for the same rise on the cam, and it is the axial movement of the grinding Wheel that controls the amount of clearance ground on the drill behind the cutting edges or lips.

It is sometimes desired that this clearance be increased or decreased in special cases for the same size of drill, and for the same setting of the indicator dial 132. Therefore, it is desirable that the bracket 140 be susceptible of vertical adjustment independent of the adjusting screw 116. Therefore, the screw 141 is made hollow or tubular and a depending shaft 147 is fitted in the tubular screw 141 and provided with a keyway 148 which is engaged by a set screw 149 mounted in the flanged end 144 of the screw 141. This permits the set screw to slide up and down in the keyway 148 whenever adjustment is effected by the handle 126, but, at any time, the shaft 147 may be rotated to impart rotation to the screw 141 and thereby raise or lower the bracket 140 relative to the bracket 110. To this end the shaft 147 extends through the fixed housing 117 where it is provided with a pinion gear 150 which is in mesh with an internal gear 151 formed in the rotatable dial 152 mounted on a supporting pivot 153 threaded in the housing 117. Thus, by rotation of the dial 152, independent adjustment may be effected by the fulcrum roller 139, and thus the axial movement of the grinding wheel may be changed relative to its lateral movement.

The mechanism for supporting the work piece and indicated generally by the reference numeral 65 in FIG- URE 1 is shown more particularly in FIGURES 10 and 11. As shown in FIGURE 1, a knee 154 is supported on the bed of the machine, and this knee is provided with a horizontal dovetail guideway 155 in which is mounted a work slide 156 for movement toward and from the grinding wheel. The slide 156 has a dovetail guideway 157 formed therein which, as shown in FIGURE 1, extends at right angles to the guideway 155. Mounted in the guideway 157, as shown in FIGURE 10, are two

slidable members

158 and 159 which have threaded

bores

160 and 161. The bore 160 is threaded to the opposite hand of the bore 161, and an adjusting screw 162 having opposite threaded

portions

163 and 164 is threaded in the

members

158 and 159 wherebyupon rotation of the screw 162 the

members

158 and 159 will be drawn together or separated, depending upon the direction of rotation of the screw 162.

The screw 162 extends through an angle bracket 165 attached to the slide 156 and the screw 162 is provided with a reduced threaded portion 166 and upon one side of the bracket is threaded a collar 167, and on the other side an operating knob 168. The

members

158 and 159 have

work clamping members

169 and 170 secured thereto as by clamping screws 171. The

members

169 and 170 have V

notches

172 and 173 formed in the opposing faces thereof in which the work piece 29 is mounted and clamped by operation of screw 162 The slide 156 is provided with a rack 174 on its underside which meshes with a gear 175 keyed to a shaft 176 as shown in FIGURE 1. The shaft 176, as shown in FIGURE 2, extends through the side of the knee and is provided with an operating handle 177 whereby upon actuation of the handle the gear 175 will be rotated to move the work piece toward or from' the grinding wheel. The end of the slide 156 carries amicrometer adjusting screw 178 which has a graduated rotator 179 splined on the screw which is movable relative to a fixed arrow 180. A spring 179' is interposed between the rotator and the head 180 of the screw. The adjusting screw is provided with a fine thread which is threaded in a nut 181 carried by the slide 156, and the end of this screw is adapted to engage an abutment 182 formed on the knee 154 to act as a stop and limit the movement of the work toward the grinding wheel. After a predetermined amount of grinding time, the micrometer screw may be adjusted and the work moved in again, until it hits the stop, by the control lever 177. By this means any number of increments of stock may be removed from the. end of the drill.

Mechanism is also provided on the knee for rotatably locating the drill to orient it in a proper starting position. This mechanism comprises a swinging arm 183 shown in FIGURE which is rotatably mounted on an eccentric boss 184 of a supporting pin 185. The supporting pin 185 has reduced ends which are mounted in a bifurcated bracket 186 (see also FIG. 2) projecting from the side of the knee 154. The arm has a projecting lug or stop 187 which is adapted to engage the wall 188 of the knee 154- when the arm 183 is swung counterclockwise by a spring 189. The arm 183 has a gooseneck extension 191 in the end of which is formed a bore 191 for receiving a work positioning thimble 192. The thimble has a conical depression 193 formed therein as shown in FIGURE 14 for receiving the end of a drill, such as 29. In this depression is formed a suitable radially extending stop 194 which is adapted to engage a lip on the drill.

It will be understood that the member 192 can be oriented in any suitable position to rotatably position the drill in accordance with the orientation of the cam member on the carrier 53. When this is done, the memher 192 may be clamped in position by suitable set screw means such as 195 as shown in FIGURE 13. The arm 183 is moved into the position shown in FIGURE 10 by the operator whenever it is desired to locate a new work piece, and the arm 183 is provided with a stop pin 196 engaging a fixed surface 197 on the knee 154-. This stop member may be adjusted by set screw means indicated by the reference numeral 198. Thus, when the arm 183 is rotated clockwise to position the locator 192 its axial center may be aligned with the theoretical center 199 of the work as determined by the

jaws

172 and 173. It will be understood that the arm 183 is swung into position and then the slide 156 is advanced by its operating lever 177 to insert the end of the drill into theslocater. When this is done, an offset arm 201' (FIG. 11) on a spring pressed lever 211i mounted on the side of the carriage 156 will be inserted in a slot 292 formed in the face of the lever 183. The lever 200 is pivotally mounted on a supporting pin 203 which is threaded in the member 156 and provided with a spring 204 which urges the lever toward the right as viewed in FIGURE 11. A pin 265 mounted in the slide 156 engages one end of the lever 260 to prevent its rotation about its supporting pin 263. Therefore, as the slide 156 is advanced, the portion 201 will enter the slot 202 and bear against the wall 205' of the. slot 202' and urge the stop pin 196 against the locating surface 197. To limit advance of the slide 156, the lever arm 183 is provided with a stop screw 29 7 which is threaded therein to project into the slot 2132 and in alignment with the member 201. When the drill has been properly located, the clamping jaws 169 and 171 are tightened to clamp the drill in the slide 156 and then the slide is retracted so that the lever 183 may be swung out of position as shown in FIGURE 2 to permit grinding of the drill.

It is, of course, necessary to true the grinding wheel, but the specific type of truing mechanism forms no part of the present invention except that it is desirable to select a truing position for the grinding wheel and provide means to stop it in that position. It is contemplated to mount the truing mechanism on the support 57, and therefore it is movable therewith. As shown in FIGURE 12, the grinding wheel continuously moves in a circular path 208 about the axis 64 of the rotatable carrier 53. Means are provided for stopping the grinding Wheel in a vertical plane about the center 64 of the carrier 53 with the understanding that the truing tool will move in this vertical plane which will coincide with a diametrical plane of the grinding wheel. Of course, this truing tool will move at an angle in this plane parallel to the conical surface of the wheel.

To this end of the rotary carrier 53 is provided with a locating notch 209 in its periphery .as shown in FIG- URE 12 and the support or slide 57 is provided with a stop plunger 210 having a roller 211 mounted in the end thereof. The plunger is mounted in the support 57 on a radius from the center 64 and a set screw 212 is threaded in the support 57 having a projecting end 213 which fits in a slot 214 to prevent rotation of the plunger 210 and to hold the axis of rotation of the roller 211 parallel to the axis 64-. A spring 215 is interposed between a washer 216' and a non-metallic switch actuator 217 which is backed up by a nut 218 threaded on the end of the plunger. The switch actuator 217 engages a springlike arm 219 which is adapted to actuate a limit switch 220. Normally, the spring 215 holds the plunger 211) in a retracted position sufiicient for the roller 211 to clear the carrier 53. In axial alignment with the plunger 210 is a control plunger 221 which has a bore 222 and a slightly smaller bore 223. A headed rod 224 is slidably mounted in the bore 223, and its enlarged head 225 engages the end of a spring 226- mounted in the bore 222. A threaded plug 227 is threaded in the end of the bore 222 to hold the spring compressed.

The plunger 221 is slidably mounted in a bushing 228 weided or otherwise secured to a fixed part of the machine, and the bore 229 of the bushing has an axially extending slot 231) formed therein. The plunger 221 has a stud 231 secured in its periphery .andnormally the plunger 221 is inserted in the bore 229 with the stud 231 in register with the slot 230. The plunger is normally held in this position by a spring pressed pin 232 shown in FIGURE 5 which is mounted in bushing 228 and engages an indentation 233 formed in the periphery of the plunger 221. This locates the parts so that the end of the member 224 is in engagement with the endof the plunger 210 and the spring 215 is strong enough to overcome the spring 226 and thereby hold all of the parts in a sufficiently retracted position that the roller 211 clears the carrier 53 and the limit switch 220 is open. When it is desired to stop the machine for truing, the operator pushes on the plunger 221 to complete movement of the stud 231 through the bushing and then the operator turns the plunger 221 until the stud 231 engages notched recess 234 formed on the inside end of the bushing 228. This compresses the spring 226 sufiiciently to urge the roller 211 into engagement with the periphery. ofv the rotatable carrier 53. When the notch 209 comes opposite the roller 211, the plunger 210 is shifted to the left as viewed in FIGURE 12, and the switch lever 219 is operated to close the limit switch 220.

When the limit switch 220 closes, it completes an 1 1 electrical circuit, indicated generally by the reference numeral 235 to a solenoid 236.

Referring to FIGURES 6 and 7, the solenoid 236 has its plunger 237 operatively connected by a bell crank 238 to the upper end 239 of the clutch shifter fork 100 which is pivotally mounted at 240. It will now be seen that when the solenoid is energized, the plunger 237 will move downward as viewed in FIGURE 7 and rotate the shifter fork to disengage the clutch teeth 95 and thereby disconnect the clutch member 96 from the driving gear 94 against the resistance of spring 98. It will be realized that the clutch member 96 is keyed to the shaft 62 and gear 61 as shown in FIGURE 2 and that this shaft does not rotate at a very high speed. Therefore, as soon as the clutch member is disengaged, the friction of the rotating parts driven by the gear 61 will immediately start to slow down. However, to insure that the clutch member 96 stops almost immediately, the face 241 is serrated with radial grooves, and a knife-edged plunger 242 is supported in position for engaging these grooves when the clutch member 96 is shifted to the right, as viewed in FIG. 6, to immediately stop rotation of the carrier 53 and with suflicient accuracy to place the grinding wheel in its truing position.

When the operator desires to start the machine again he merely turns plunger 221 until the stud 231 is aligned with the slot 230 whereby the spring 215 will return the parts to their starting position and deenergize the solenoid 236.

In the operation of the machine, the motor is started and runs continuously, operating the parts connected thereto. The general layout of the cams which control the lateral and axial movements are shown in FIGS. 15 and 16. As shown in FIGURE 15, the lateral control cam 106 rotates clockwise, and is spring held against the roller 105. The cam is shown in its midposition with its axis 64 coaxial with the axis 66 of the drill shown above the cam. In other words, the radius R is equal to the radius R of the cam. At the same time, the roller 103 (FIG. 16) is in engagement with the lowest point of the axial control cam surface 104. Since the cam 104 is spring held against the roller 103, this means that the grinding wheel support is spaced axially its greatest distance from the drill.

The cam 106 has a profile such that when it is rotated clockwise a few degrees so that the point 243 engages the roller 105, a quick positioning movement is effected which places the grinding wheel in the position shown in FIGURE 18. Simultaneously, the rise on cam 104 effects an axial shifting of the grinding wheel toward the work, so that the grinding wheel just touches the work. The axis 64 which is the generating axis now moves to the left of the drill axis 66 as viewed in FIGURE 15. This corresponds to the shifting movement along the axis 26a referred to in connection with FIGURE 17.

The radius of the cam 106 decreases from the point 243 to about the point 244, which means that the axis 64 continues to move to the left, while the rise on cam 104 continues to move the grinding wheel toward the work, and the grinding wheel continues to move about the axis 64 and reaches the position 20a--20a shown in FIGURE 17. This completes the grinding cycle for one lip. The cams continue to rotate and effect a repositioning movement and then repeat the generative grinding cycle.

During the second grinding cycle, attention is invited to the fact that the section of the cam 106 from point 245 to the point 246 is of constantly increasing radius, due to the fact that the axis 64 is now being moved to the right of the drill axis. Therefore, the cam has two sections, one of decreasing radius, and one of increasing radius. The axial movement is the same in each case.

There has thus been presented a new and improved method and apparatus for generative grinding of drills.

What is claimed is:

1. The method of pointing the end of a drill by rotating a grinding wheel about its own axis, said grinding wheel having a grinding face thereon made up of a succession of generative line elements, and relatively bodily moving the grinding wheel face and the end face of the drill while in mutual contact in an orbital cycle, one about the other, in a conical spiral path, the drill and grinding wheel being positioned at the beginning of the cycle with a generative line element in the grinding face of the wheel intersecting the axis of the drill at an acute angle with one finite end of the element extending beyond the axis of the drill a predetermined amount, and continuing said movement in a conical spiral path until and after said finite end passes through said drill axis.

2. The method of grinding the cutting face of a fluted drill by means of a grinding face on a rotatable grinding wheel, said grinding face having an active generative line element lying in a radial plane containing the axis of the wheel, said line element terminating in angular relation to a reference axis lying in said radial plane containing said wheel axis, positioning the drill with its axis intersecting the active line element with one finite end of the element extending beyond the axis of the drill a predetermined amount and with the axis of the drill parallel to said reference axis with its cutting face in tangential relation to said grinding face along a line on the cutting face of the drill passing through an intermediate space of a drill flute, gyrating one of said faces relative to the other about one of said parallel axes, and simultaneously effecting relative bodily movement between said faces in directions axially and laterally with respect to said axis of gyration to cause the said one finite end of the active line element to move through the drill axis and a predetermined amount therebeyond while the cutting face of the drill moves toward the grinding face of the wheel.

3. The method of grinding the cutting face of a fluted drill by means of a grinding face on a rotatable grinding wheel, said grinding face having an active generative line element lying in a radial plane containing the axis of the wheel, said line element terminating in angular relation to a reference axis lying in said plane, positioning the drill with its axis intersecting the active line element with one finite end of the element extending beyond the axis of the drill a predetermined amount and with the axis of the drill parallel to said reference axis with its cutting face in tangential relation to said grinding face along a line passing through an intermediate space of a drill flute, gyrating one of said faces relative to the other about one of said parallel axes, and simultaneonsly moving said axis of gyration and thereby one of said faces axially and laterally relative to the other to effect two directional movement therebetween to cause the said one finite end of the active line element to move through the drill axis and a predetermined amount therebeyond while the cutting face of the drill moves toward the grinding face of the wheel.

4. In a drill grinding machine having a base and a drill holding fixture thereon, the combination of means for supporting a grinding wheel on the base for relative movement with respect to the fixture comprising a grinding wheel spindle, a rotatable carrier supporting said spindle therein parallel to but eccentric of the axis of rotation of the carrier, a sub-support mechanism for support ing the carrier on the base for bodily movement in nor mally related directions, and means to impart rotation and said bodily movements to the carrier simultaneously.

5. In a drill grinding machine having a base and a drill holding fixture thereon, the combination of means for supporting a grinding wheel on the base for relative movement with respect to the fixture including a grinding wheel spindle, a rotatable carrier supporting said spindle therein parallel to but eccentric to the axis of rotation of the carrier, means to impart rotation to the spindle, means to impart rotation to the carrier, and means to impart bodily movement to the carrier in two normally related directions simultaneously during rotation of the spindle and carrier.

6. In a drill grinding machine having a bed, means to support a drill with its axis parallel to the plane of the bed, a sub-support guided on the bed for two directional movement parallel to the plane of the bed, a rotatable carrier journaled on the sub-support for rotation about an axis parallel to the plane of the bed and to the drill axis, a grinding wheel spindle journaled eccentrically in the carrier with its axis parallel to the axis of the carrier, and power operable means for rotating said carrier and simultaneously imparting two directional movement to said subsupport in prescribed synchronized relation.

7. In a drill grinding machine having a bed, means thereon to locate and clamp a drill in grinding position, a rotatable carrier supporting a grinding wheel, means mounting the carrier on the bed with its axis of rotation co-axial with the axis of the drill, means to laterally oscillate the carrier equal distances to either side of said drill axis, and means to impart movement to the carrier parallel to its axis simultaneously in one direction as the carrier axis moves away from the drill axis, and in an opposite direction as the carrier axis moves toward the drill axis.

8. In a drill grinding machine having a base, and means thereon for locating and clamping a drill to be ground, the combination of a grinding wheel spindle, a rotatable carrier supporting said spindle eccentric to its axis, a sub-support for supporting said carrier on the base with its axis coaxial of the drill axis, means to impart movement to the carrier parallel to and normal to its axis including control cams attached to said carrier, a follower roller for each cam, a lever arm supporting each roller and pivotally connected to the sub-support, and a fulcrum roller carried by the bed in engagement with said levers.

9. In a drill grinding machine having a base, and means thereon for locating and clamping a drill to be ground, the combination of a grinding wheel spindle, a rotatable carrier supporting said spindle eccentric to its axis, a sub support for supporting said carrier on the base with its axis coaxial of the drill axis, means to impart movement to the carrier parallel to and normal to its axis including control cams attached to said carrier, a follower roller for each cam, a lever arm supporting each roller and pivot ally connected to the sub-support, a fulcrum roller carried by the bed in engagement with said levers, and means to shift said fulcrum rollers parallel to said levers.

10. In a drill grinding machine having a base, and means thereon for locating and clamping a drill to be ground, the combination of a grinding wheel spindle, a rotatable carrier supporting said spindle eccentric to its axis, a sub-support for supporting said carrier on the base with its axis coaxial of the drill axis, means to impart movement to the carrier parallel to and normal to its axis including control cams attached to said carrier, a follower roller for each cam, a lever arm supporting each roller and pivotally connected to the sub-support, and a fulcrum roller engaging each of said lever arms and carried by the bed, and means to independently shift said fulcrum rollers parallel to their respective lever arms.

ll. In a drill grinding machine having a base, and means thereon for locating and clamping a drill to be ground, the combination of a grinding wheel spindle, a rotatable carrier supporting said spindle eccentric to its axis, a sub-support for supporting said carrier on the base with its axis coaxial of the drill axis, means to impart movement to the carrier parallel to and normal to its axis including control cams attached to said carrier, a follower roller for each cam, a lever arm supporting each roller and pivotally connected to the sub-support, and a fulcrum roller engaging each of said lever arms and carried by the bed, means to simultaneously shift said fulcrum rollers parallel to their respective lever arms, and additional means to shift one of said rollers independently of the other.

12. In a drill grinding machine having a bed, means thereon to support and clamp a drill to be ground, a

grinding wheel spindle, a rotatable carrier for supporting position for truing the grinding wheel includinga spring pressed plunger, said carrier having a locating notch thereon in predetermined relation circumferentially with respect to the axis of the spindle, means to release said plunger for engagement with said notch, and electrical means automatically operable upon engagement of the plunger with said notch to stop rotation of the carrier.

13. The method of grinding the cutting face of a fluted drill by rotating a grinding wheel about its axis, said grinding wheel having a grinding face thereon made up of a succession of generative line elements extending crosswise of said face and terminating in a radius formed by a rounded corner on the wheel, positioning a portion of the cutting face to be ground in opposition to and in grinding relation with said grinding face and with the axis of the drill intersecting the grinding face at a predetermined angle, eifecting rotation of the grinding wheel, and while the wheel is so rotating, effecting a gyratory movement between said opposed faces while maintaining said angle constant to effect a grinding operation and to generate a surface in accordance with the shape of said line elements, and simultaneously effecting an additional relative movement between said faces both in the direc tion of the axis of the drill and also normal thereto to cause said radius to move through and beyond the axis of the drill and thereby'eifect the shaping of a point on the axial end of the drill, and controlling said gyratory, movement in timed relation with said additional movement to cause grinding of a spiroidal surface on the cutting face simultaneously with the shaping of said point.

14. The method of generating a cutting face on the end of a fluted drill having a cutting edge extending cr0ss-. wise of its axis between the bottom of said flutes and connected at its ends to the lips of the drill with onehalf of each side face of the cutting edge forminga cutting face and the other half a flank face, said method comprising rotating a grinding wheel havinga grinding face about its own axis, said grinding face being made up of asuccession of generative line elements extending crosswise of said face and terminating at one end in a radius formed by a rounded corner on the wheel, and relatively moving the grinding face of the wheel and the cutting face of the drill while in mutual contact in a conical spiral path, the grinding face of the wheel and the cutting face of the drill being positioned at the beginning of the cycle with a line element in the grinding face intersecting the axis of the drill with the radius end of the element extending beyond the axis of the drill a pr determined amount, and continuing the relative spiral movement of the grinding Wheel and drill until and after the radius end of the element passes through and beyond the drill axis whereby the rounded corner will grind a spiroidal surface on the flank face and the cutting face on one side of said cutting edge While said grinding face grinds a conical spiral surface on the end of said drill.

15. The method of generating a cutting face on the end of a two-flute drill having a cutting edge extending crosswise of its axis between the bottom of said flutes and connected at its ends to the lips of the drill with one-half of each side face of the cutting edge forming a cutting face and the other half a flank face, said method comprising rotating a grinding wheel having a grinding face about its own axis, said grinding face being made up of a succession of generative line elements extending crosswise of said face and terminating at one end in a corner on the wheel, and relatively moving the grinding face of the wheel and the cutting face of the drill while in mutual contact along a conical spiral path while rotating the drill relative to the wheel through an angle of more than 90 degrees and less than 180 degrees, the grinding face of the wheel and the cutting face of the drill being positioned at the beginning of the cycle with a line element in the grinding face intersecting the axis of the drill with the one end of the element extending beyond the axis of the drill a predetermined amount, and continuing the relative spiral movement of the grinding wheel and drill until and after the one end of the element passes through and beyond the drill axis whereby said one end first will grind a spiroidal surface on th flank face and the cutting face on one side of said cutting edge while the grinding face grinds a conical spiral surface on the cutting face of the drill.

16. The method recited in claim wherein said one end of the generative line element is terminated in a radius formed by a rounded corner on the wheel.

17. The method recited in claim 16 wherein the angle made by the axis of the drill with the face of the grinding wheel is maintained constant during relative movement of the grinding face and the drill along said conical spiral path.

18. The method recited in claim 16 wherein the grinding wheel and drill are positioned with their axes parallel to one another, and wherein said axes are maintained in such relationship during said relative movement of the grinding face and the drill.

19. In a drill grinding machine, the combination of a bed, a carrier mounted on said bed for rotary, axial and lateral movements either individually or in combination, a grinding wheel spindle journaled on said carrier with its axis parallel to but displaced from the axis of said carrier, means to rotate said carrier, and means operating in synchronism with the rotation of said carrier for imparting timed axial and lateral movements thereto whereby said grinding wheel spindle will be given corresponding axial and lateral movements as it is gyrated about the axis of said carrier.

20. In a drill grinding machine, the combination of a bed, a support mounted on said bed for movement in two mutually perpendicular directions, a carrier journaled in said support for rotation about an axis parallel to one of said directions of movement, a grinding wheel spindle journaled on said carrier with its axis parallel to but displaced from the axis of said carrier, means to rotate said carrier, and means operating in synchronism with the rotation of said carrier to move said support in said two directions whereby said grinding wheel spindle will be given coordinated axial and lateral movements as it is gyrated about the axis of said carrier.

21. In a drill grinding machine for generating a cutting face on the end of a drill having longitudinally extending flutes and a cutting edge extending crosswise of its axis between the bottom of said flutes with one half of each side face of the cutting edge forming a cutting face and the other half a flank face, the combination of a grinding wheel having a grinding face thereon made up of a succession of generative line elements extending crosswise of said grinding face and terminating at one end in a radius formed by a rounded external corner on the wheel, means for holding the drill with its cutting face in tangential relation to the grinding face and with the axis of the drill intersecting one of said generative line elements, cyclically operable means for effecting relative rotation between the grinding face of the wheel and the cutting face of the drill, and means including a pair of cams operated by said cyclically operable means for imparting timed lateral and axial movements of the grinding face relative to the cutting face to cause the rounded corner to move across the axis of the drill and in so doing to grind the flank face and the cutting face on one side of the cutting edge While the grinding face simultaneously grinds a conical spiral surface on the cutting face of the drill.

22. The drill grinding machine of claim 21 wherein said movement imparting means includes a cam follower for each of said cams, and manually adjustable means cooperating with said cam followers for varying the effective throw of said cams whereby the machine may be adjusted to grind different size drills.

References Cited in the file of this patent UNITED STATES PATENTS 546,041 Tyberg Sept. 10, 1895 641,107 Heister Jan. 9, 1900 1,652,672 Jackson Dec. 13, 1927 1,759,196 Jackson May 20, 1930 2,328,549 Eich et al. Sept. 7, 1943 2,471,539 Parker May 31, 1949 2,529,026 Kestell Nov. 7, 1950 2,538,651 Parker Jan. 16, 1951 2,869,403 Bemt Jan. 20, 1959 2,903,922 Ernst et al Sept. 15, 1959 FOREIGN PATENTS 250,713 Switzerland July 1, 1948 1,006,695 France Jan. 30, 1952