CA1049789A - Drill grinding device - Google Patents

Abstract

DRILL GRINDING DEVICE

Abstract of the Disclosure A device for positioning, holding and feeding twist drills and the like to a grind stone to grind the bevels of the faces of the drill accurately and symmetrically is dis-closed.

A drill locking means has a bed for holding the drill and a fence to restrain it in one direction. A finger which has means forming an inclined plane on one side and which comes to a point near the fence is carried by the bed.
The flute trailing edge of the drill engages the inclined plane at various points depending on the drill size. The force of the grind stone rotates the flute trailing edge against the inclined plane. There is also an adjustable drill stop to provide longitudinal drill positioning. The combination of bed, fence, finger and drill stop locks the drill in place against the grind stone during the grinding operation. To grind the opposite face, the drill is rotated approximately 180° and replaced. The moving grind stone will urge the drill into exact 180° opposition in the drill lock-ing means, automatically.

The drill is fed in a straight line into the stone by means of nesting troughs. The drill locking means in trough form with the drill in place can be removed for inspection or quenching of the drill and returned to the same position.

means for controlling the forward excursion of the drill is provided by a threaded screw carried by one of the troughs which bears against the other trough. A tension bar tightens by rotation against the carrying trough to hold the screw in place.

Description

10~9~;~8~
B~C:~GROUNV O~ IE INV:I'NTION
_._ _ _ 1. Field of the Invention My invention relates to drill sharpeniny devices, and particularly to means and methods of posi-tioning a drill in the proper grinding attitude with respec-t to a grinding stone, grip-ping it and feeding it to the stone with the object of grinding the bevels of the face of the drill point precisely and symmetri-cally.

2. The Prior Art The basic combination of elements used in ordinary shop drill sharpening devices except for various improvements to the basic design is exemplified in U.S. Patent No. 751,198 issued February 2, 1904. There are several problems in the prior art machines which will be explained in succeeding paragraphs.
In sharpening twist drills and the like it is desir-able to completely immobilize the drills during the grinding operation and, when one face of the drill is ground, to rotate the drill precisely 180 to grind the other face ph/jl 1 and to remove equal amounts of both faces. The symmetry of 2 the drill and balanced cutting lips of the faces depends upon

3 the accuracy with which the 180 rotation is accomplished.

4 The prior art drill devices can not reliably position and immobilize the drill and reposition it at exactly 180 6 rotation for grinding the opposite face.
8 In most types of drill sharpening devices, the 9 drill locators are not adequately effective as a guide to accurately position the drill for the proper sharpening 11 attitude, and they are incapable of accommodating drills 12 from 1/8 inch through 1/16 inch in diameter. They either 13 engage the side of the flute or the deepest recess of the 14 web and neither of these surfaces is a reliable means to stabilize and prevent lateral movement of the drill. Further-16 more they must be adjusted to compensate for each size drill 17 which is a contributing factor to additional time consuming 18 steps. Because there is no need to accurately machine the 19 web for drilling efficiency, the manufacturer may leave variations rom one side of the web to the other. This often 21 prevents an exact 1~0 repositioning of the drill relying on 22 the web. Assuming that the web is uniformly machined on 23 both sides of the drill (a rare occurrence), the surface of 24 the web presents a concave surface in which a drill will move several degrees in either lateral direction even if 26 the drill locator is engaged in the deepest recess of such 27 a surface. The shallower the concavity the more pronounced 28 such movement becomes. Oxidation of one surface or the 239 other is an additional hazard to accuracy.

. ~ . . . :

l ~

10~9789 1 For examples of prior art locators, see U. S. Patents 2 numbered 641,107, 2,384,859 and 2,583,159. The locators func-3 tion as a mark or reference point and the drill is positioned 4 against the mark; then the clamp is screwed down to secure the drill. There are two disadvantages in this arrangement;
one is that the drill is subject to some lateral movement 7 either while being held by the hand or during tightening 8 by the clamp itself as it applies pressure against the drill.
9 The same phenomenon applies in rotating the drill to sharpen the other side. Since some locators are flexible and yield 11 to light lateral forces, such instability further increases 12 lateral movements. It is difficult to prevent lateral move-13 ments as a result of grinding pressures, or to obtain precise-14 ly 180 repositioning to grind the second face of the drill.

16 A major disadvantage of the prior art devices is 17 that they depend upon the principle of oscillating or rocking 18 the drill stock into the periphery of the grinding wheel.
19 This has dangerous and otherwise undesirable consequences.
~0 For one thing it brings only one small area of the drill 21 stock in contact with the grinding wheel. This produces 22 a pinching or jamming effect against the wheel and places 24 a strain on the motor~ The result can be chipping or gouging of the grinding wheel. The oscillating principle and its application also causes the drills to wear a groove 26 in the grinding wheel because onl~ a small part of the drill 27 surface is in contact during the early stages of grinding.
28 Moreover, since there is only a small area in contact, heat 230 builds up very rapidly at that point. Thus the grinding ~2 1~9713~
1l operation must be repeatedly interrupted to allow the parts 2I to cool which in turn extends the time required for the 3I sharpening operation.

Another problem encountered in prior art machines 6 is that drills of different sizes used in succession require 7 time-consuming readjustments of the machine.

9 Another prior art disadvantage is the complexity of some of the machines, which among other things makes them 11 quite costly.

13 It is an object of this invention to overcome the 14 disadvantages of the prior art devices.

18 My invention represents a radical departure from 19 the prior art teachings. In combination, I have provided a device for grinding twist drills and the like to be used in 21 cooperation ~with a grinding stone apparatus, the essential 22 elements of which are as follows: drill locking means 23 comprising a fence and an adjacent bed, a finger carried by 24 said bed and coming to a point close to but not touching the 25 fence, said finger adapted to engage the flute trailing edge 26 of a drill to be held by the drill locking means, and longi-27 tudinal drill positioning means.

?9 Considered in another aspect the drill locking 31 means is a feed trough or drill carriage having two sides _5_ 1 I which come together at an apex, the angle of the apex not 2 being critical but conveniently 90. The one side of the 3 trough can be thought of as a drill-supporting bed and the 4 other side can be considered a drill-restraining fence. The finger is disposed on the bed near the point of the drill 6 and attached at the end of the trough closest to the grind-7 ing stone. It comes to a point with about l/32 inch clear-8 ance between the point and the fence at the apex angle.
9 The finger has an inclined plane on one side coming to the 10 I point of the finger, and its function is to engage the flute 11 trailing edge of the twist drill as distinguished from the 12 edge of the lip or the web. The pressure and rotation of 13 the grind stone on the drill face being ground serves to 14 lock the drill into place by rotating the drill against the inclined plane of the finger which causes it to engage and 16 lock against the trailing edge of the flute. The finger is 17 firmly affixed in place on the bed so as to receive the 18 rotational pressure of the drill in the grinding operation 19 substantially longitudinally of the finger and firmly main-tain its position and structure. A small wedge is removed 21 from the underside of the point of the finger next to the 22 bed to accommodate the trailing flute edge of the smaller 23 twist drills. Thus, all normal sizes of twist drills can be accommodated in the drill locking means and successfully retained by the finger automatically without adjustment of 26 the finger. As a result, drill sharpening is more simplified, more accurate, and less time-consuming.

2 To precisely position the drill, simplified longi-32 tudinal drill positioning means are provided. These may be 1049'789 1' in any one of several forms and the preferred embodiment will 2 be later explained. An essential requirement is that an 3 adjustable drill stop be provided as a reference point for 4 the longitudinal positioning of the drill.

6 A preferred embodiment of the adjustable drill stop 7 comprises a block slideably disposed in the feed trough at 8 its inner apex, a bridge slideably disposed on the sides of 9 the trough and a set screw disposed in the bridge such that the end thereof can be brought to bear on the block. The 11 set screw can be loosened so that the block and bridge can 12 slide longitudinally along the feed trough. When the desired 13 position is reached, the set screw is tightened against the 14 block which in turn causes it to frictionally engage the sides and apex of the feed trough, thus provided a rear stop 16 to the drill.

18 A novel feed mechanism for advancing the drill in 19 a straight line to the stone which permits the drill to be removed entirely for examination or quenching is provided.
21 The mechanism is a combination of drill locking means and 22 support means upon which the drill locking means removeably 23 rests. An example is a support trough conforming to the 24 shape of the feed trough which slideably receives the feed trough. Thus the feed trough can be made detachably mounted 26 to the support trough which is fixed in place in operational 28 relationship to a grind stone.
29 A convenient and desirable additional element of the longitudinal drill positioning means and an important sub-31 combination of this invention is the adjustable feed trough 1049~t~9 1 ¦ stop. The preferred embodiment of this sub-combination 2 I comprises a mounting block anchored to the feed trough, said 3 mounting block being tapped to receive a threaded bolt, a 4 tension bar also tapped to receive, and being carried on, the threaded bolt can be rotated on the bolt and tightened 6 against the anchor block to lock the bolt in place, the end 7 of the bolt bearing against the rear of the support trough 8 at a desired point in the forward excursion of the feed trough.

Slight pressure of the operator's finger against the 11 shank of the drill will suffice to dampen vibration or mechan-12 ical means can be provided to perform this function.

14 The device of this invention is simpler, requiring fewer adjustments, and is considerably cheaper to manufacture.
16 This machine will rapidly sharpen any drill any size or length 17 with precision approaching or equalling professional machines 18 of much greater cost.

It is adapted to function with an electric motor 22 and frontal mounting plate, or as a separate attachment to existing home or shop type standard grinding machines and 23 can employ either the facial or lateral surfaces of said 24 grinders to grind the bevels of the drills.

26 The foregoing comprises but a brief description of 27 the important parts of the invention, and further refinements 28 and modifications will be described hereafter in the descrip-tion of the preferred embodiments.

.' ,, , 3 A more detailed understanding of the invention will 4 be gained from consideration of the appended drawings in which:

6 Fig. l is a perspective view of the presently 78 preferred embodiment of this invention;

9 Fig. 2 is a side elevation view of the device of Fig. l 12 Fig. 3 is a view of the device of Fig. 2 along the 13 lines 3-3;
14 Fig. 4 is a view of the device of Fig. 2 along the 17 lines 4-4;
18 Fig. 5 is a view of the device of Fig. 2 along 290 the lines 5-5;
21 Fig. 6 is an enlarged fragmentary view of the part 222 f the device of Fig. 5;

Fig. 7 is a perspective view of the finger;
26 Fig. 8 is an elevation view of the embodiment of 278 Fig. 7;

29 Fig. 9 is a perspective view of an alternative embodiment of the finger;

~2 - _9_ ~ . :, . ~' . , .
:,, ' - ' : ' 10~9789 1 Fig. lO shows a fragment of the device of Fig. 1 2 in a second alternative finger embodiment;

4 Fig. 11 is a view of the device of Fig. l along the lines ll-ll;

7 Fig. 12 is a view of the drill position to be 8 attained as an aid to aligning the drill for sharpening.

A perspective view of the complete device is shown 11 in Fig. 1. The grinding wheel 1 is shown attached to an 12 associat~d motor 3 by means of a power takeoff shaft 5 13 journaled in the mounting plate 7 of a frame 9. The frame 9 14 may be bolted to a deck 11 by bolts 13, but for most purposes it will be found that my device may be utilized successfully 16 without bolting to the deck, and furthermore may be used as 17 a portable drill grinding device which can be moved from 18 place to place in the shop. As better shown in Fig. 2, the 19 frame 9 supports the lower support trough 15 by means of a standard 17 rotatably secured in an apperture ~not shown) 21 in the tongue 19 extending forwardly of the mounting plate 7.
22 The standard 17 is locked tight against the tongue l9 with 23 one nut 20 above and a second nut 22 below the apperture in 24 the tongue l9. By loosening the lower nut 22 slightly, the support trough 15 may be rotated in a horizontal plane, 26 permitting the operator to select any angulation desired for 27 the point angle of the drill. The bottom nut 22 is then 28 tightened and the support trough remains in a rigid immovable 29 state at the selected angle. In the case of an existing unit .

1 the tongue 19 corresponds to a tool rest, and it will be under-2 stood that the entire unit can be removed simply by removing 3 the second nut 22 below the tongue (tool rest). Attachment 4 to alternative apperture 23 in the tongue permits the unit to be used on either the face 2 or side 4 of the grinding 6 wheel 1. In side grinding position it is recommended that 7 a type VI wheel, recessed on one side, such as put out by 8 the Norton Grinding Wheel Co. be used. A 60 grit wheel is 9 ideal for sharpening drills.

11 Extending from the standard 17 is an indicator 21 12 which in conjunction with graduated marks 23 (Fig. 3), indi-13 cates the degree of rotation of the trough 15. The upper end 14 of the standard 17 is journaled in ear 25 which in turn is attached to the outer apex of the lower support trough 15.
16 The trough 15 can be vertically rotated about the journal 17 pin 29 to obtain the desired heel relief angulation. The 18 journal pin carries an indicator 31 which in conjunction with 19 degree markings 33 indicate the inclination of the support trough 15 relative the horizontal.

22 Referring again to Figs. 1 and 2, an important 23 sub-combination of this invention is the combination of the 24 lower support trough 15 and the feed trough 35 comprising fence 37 and bed 39. As can be seen from Fig. 1 the feed 26 trough 35 can be slideably reciprocated to and from the 27 grinding wheel 1 in the lower support trough 15. As afore-28 mentioned this is a decided improvement over the oscillating 29 drill carriage because the drill face can be moved squarely into the grinding stone with optimum surface contact between metal and stone.

10~9789 1 ¦ A most important sub-combination of the overall 2 invention is the combination of the bed 39 carrying the 3 finger 41 about 1/32 inch - 1/64 inch from the fence 37 and 4 adjustable drill stop 43. In this embodiment the bed 39 and fence 37 are integrally formed at a 90 angle. The 6 details of the drill stop 43 can best be seen in Fig. 4.

8 Drill stop 43 is constructed of a wedge 47 which 9 sits at the inner apex 49 of the feed trough 35. A bridge 51 spans the edges 53 of the feed trough 35, clearing the 11 wedge 47. A set screw 55 is seated in the tapped bore 57 12 and engages the upper face 59 of the wedge 47 to secure it 13 in place as desired.

The operator's finger is a convenient vibration 16 dampening means, but alternative means 45 is seen in Fig. 11.
17 It is constructed with a tapped bore 61 in the fence member 18 37, a brace 63 having a slot 65, a wing nut bolt 67 passing 19 through the slot 65 and engaging tapped bore 61. The brace may be secured after adjustment by ~his means. Fig. 1 and 21 Fig. 11 show the vibration dampening means 45 tightened on 22 a small drill. The preferred means for dampening vibration 23 in the drill, however, is a slight pressure from the opera-24 tor's hand, e.g. the thumb, against the drill in the trough 39. However, for drills of small size a dampening means 26 such as shown in the drawings is convenient.

28 The finger 41 is a very important element of this 29 invention. The finger has two parts serving differing sizes ~2 1l of drills. One part is the inclined plane 71. Depending upon 2 the size of the drill it catches the flute trailing edge of the 3 drill at various points along the inclined plane 71, as indi-4 cated by the score marks 73, transmitting the pressure of the lip of the drill as it is being ground longitudinally in the 6 direction of the arrow to the end of the finger where it is 7 firmly anchored by rivets 75 to the upper feed trough 39. A
8 second aspect of this invention useful in the handling of 9 drills 1/8 inch or smaller is the small wedge portion 77 removed from the tip 79 of the finger nearest the bed 39 11 which creates an auxiliary inclined plane~80.
12 .
13 The combination of these two features makes the fin-14 ger 41 serve as a completely reliable and stable guard against rotation of the drill in the device no matter what the size of 16 the drill, and thus completely assures that in grinding the 17 opposite face the drill will always be positioned exactly 18 180 from its first grinding position. In Fig. 6 the finger 19 41 is shown engaging the flute trailing edge 81 (heliax angle) 20 of a small drill 83. As illustrated the smaller drills make 21 purchase on the auxiliary inclined plane 80 at the end of the 22 finger.

24 It is desirable to form the inclined plane 71 with 25 a convex radius as best shown in Fig. 7, although it need not 26 be as exaggerated as shown in Fig. 7. The object is to avoid 27 engaging the flute which could occur in a drill having a slow 28 helix angle if inclined plane 71 is perfectly straight.

10~9789 1 Referring to Fig. 9, the finger is shown on a portion 2 of the bed 39. Numeral 85 indicates the inner apex line of 3 the bed and fence. Using line 85 as a reference, the preferred 4 angle phi is 45, whether the inclined plane is straight form or convex radial. Deviations of 10 degrees either way in the 6 inclined plane are quite acceptable. Greater deviations will 7 cause an increasing loss of function. As further indicated in 8 Fig. 9, the inclined plane need not be elevated from the plane 9 of the bed 39 to be operative, although some elevation is preferred.

12 The heliax angle or actual trailing edge 81 of the 13 flute of any drill size cuts across one of the inclined planes 14 71 or 80 of the finger 41. This assures a positive and non-slipping stop. The grinding wheel 1 exerts downward pressure 16 against the drill resulting in clockwise rotational force as 17 viewed facing the drill point. This force is absorbed through 18 the longitudinal axis of the finger, resulting in an unyield-19 ing retainer. The trailing edge 81 of the flute of any sized drill will cross over the inclined planes 71 or 80 at some point, 21 either forward, the center, or to the rear of the inclined 22 plane. In any case the force is absorbed substantially through 23 the long axis of the finger. Observing the inclined plane 71 24 from the bottom of the finger 41 the score lines made by various sized drills can be illustrated. At the point of the 26 finger 41 the inclined plane 71 ends in the auxiliary inclined 27 plane 80 made by removing a small wedge from the end of the 28 finger. As observed, the auxiliary plane 80 is important in 29 engaging drills less than 1/8 inch in diameter and provides 10~978~
1 purchase for such drills. This is the point where the inclined 2 plane 71 is in contact with the support bed. Consequently, 3 since there is no room behind the inclined plane 71 for the 4 flute edge to cross over, the flute edge crosses over dis-secting the auxiliary inclined plane 80 and still retaining 6 the same desirable relationship to the finger achieved by ~he 7 larger drills by dissecting the inclined plane 71.

9 The feed adjustment means 91 is disposed at the rear of the feed trough 35. The feed screw 93 is attached 11 to the underside 95 of the feed trough 35 in the tapped bore 12 (not shown) in block 97. A thread tension bar 99 is tapped 13 at one end 101 to receive the threads of the feed screw 93.

14 The feed screw 93 is rotated clockwise or counter-clockwise in the block 97 as desired to adjust the forward excursion of 16 the feed trough 35. The end 103 of the feed screw contacts 17 the rear end 105 of the support trough 15. To back up the 18 feed screw 93, the tension bar 99 is moved counter-clockwise 19 into a vertical position, with the free end 107 in the downward position. Gravity and vibration maintain it in that position 21 during subsequent adjustments of the feed screw 93. To lock 22 the feed screw in place the tension bar is rotated in a clock-23 wise direction by a flip of the finger against the bar to a 24 horizontal position as shown in Fig. 1. Again the force of gravity and vibration maintains it in a locked position. The 26 feed adjustment means is used both to control and to vary the 27 forward excursion of the feed trough 35 towards the grinding 28 surface of the wheel.

3~

1~ This feed screw is a radical feature in that it 2 employs vibration and gravity to maintain thread tension.
3 At this stage of the art, industry and engineers have treated 4 vibration as a~problem and have attempted to combat the problem through dual knurls, springs, gear trains and other costly 6 and complex means.

8 In the second case, the conventional screw feed 9 mechanism generally acts upon the drill itself, thereby imparting dimensional changes to the drill in moving it to 11 the grind stone. In contrast my screw feed mechanism acts 12 solely upon the forward excursion of the drill carriage to 13 regulate the amount of metal to be removed from the drill.
14 As a result, it increases drill sharpening accuracy but drastically decreases fabricating costs.

17 Fig. 9 shows an alternative embodiment of the finger 18 41. Again the score lines 73 are indicated on the inclined ~9 plane 71.

33o -15(a) . ., ~
.

1 Fig. 10 is another alternative embodiment of the 2 finger in relationship to the bed 39. In this case the finger 3 41 is stamped out of the metal of the support bed and again 4 ~ the score marks 73 made by the trailing flute edge of the drill on the inclined plane 71 of the finger are illustrated.

7 The device of this invention is practically fool-proof, being simple to operate and requiring fewer steps in 9 sharpening drills. Its operation is as follows:

11 Secure the drill stop 43 behind the drill stem 109 12 with the point 111 of the drill projecting out in front of 13 the feed trough 15 one-quarter inch or so. As seen in Fig. 12, 14 the correct way to position the drill for grinding on the side of the wheel is to hold the feed trough in the hand with points 16 141, 151 touching imaginary horizontal line A and points 161, 17 171 touching line B which is parallel to line A. Replace the 18 feed trough 35 in lower trough 15. Push the feed trough 35 19 forward until the drill tip 111 barely touches the grinding wheel; then manipulate the feed screw until its end 103 barely 21 touches the rear end 105 of the support trough 15. At this 22 point, the feed trough 35 cannot travel forward. Now set the 24 tension bar 99 so that it takes some physical effort to mani-pulate the feed screw 93; then turn the feed screw counter-clockwise to allow the feed trough 35 to go forward. In so 26 doing, the drill tip or point 111 is brought into contact with 27 the grinding wheel. Then a quarter turn of the feed screw 28 should be made to allow about 1/500ths of an inch of the drill 29 stock to be removed. This is sufficient for drills less than ~2 ' '` ~ :

1 1/8 inch; allow a half turn for drills larger than 1/8 inch.
2 In the case of badly distorted drills, one may require as 3 many as ten turns or more to properly dress them depending 4 upon the degree of abuse of the drill. In any event, it

5~ can be seen that the drill life can be extended considerably

6 if no more metal than necessary is removed for resurfacing.

7 The feed trough 35 is freely detachable, therefore it can

8 be backed up at will and lifted up to see exactly when the

9 entire face of the drill is freshly resurfaced, or to quench the drill in water if it is excessively hot.

12 When the drill is fully resurfaced, the end of the 13 feed screw 93 will be making contact with the rear end 105 14 of the support trough 15. Make no adjustment of the feed screw 93 at this point. Instead, back up the feed trough 16 35 an inch or so, grasp the drill with the thumb and index 17 finger. Give the drill a quick twist to free it from the 18 drill lock and spin it one-half turn; then reinsert it in 19 contact with the finger of the drill lock. The drill stem 21 109 will be in contact with the drill stop 43 to establish 22 the longitudinal positioning of the drill. All control settings on the device are left intact. This assures that 23 the drill is not subjected to dimensional changes in sharpen-24 ing the second face.

6 Now slide the feed trough 35 forward and grind the 27 second face of the drill. When the end 103 of the feed screw 1 28 93 makes contact with the rear end 105 of the support trough 15, 29 it will be impossible to remove additional metal from ~he ~2 . .

1 drill point. At this point grinding action stops and the drill 2 is thus sharpened with exact balance as to point angulation, 3 centering of the chisel line angle or point, and identical 4 heel relief bevels. In summary, it will possess ideal drill geometry.

In freeing the drill for rotation to sharpen the 8 second face the drill is twisted in the opposite direction 9 or away from the device itself and it will release and rotate freely. However, it is not necessary to rotate the drill 11 exactly 180 because the grinding wheel action will automa-12 tically twist the drill into the drill lock in a position 13 180 from the first position automatically. This feature 14 reduces positioning error$,accelerates the drill sharpening process and renders the machine nearly fool proof.

17 By experiment I have demonstrated that drills 18 sharpened on numerous prior art machines and used on hard 19 steel have a tendency to burn up under pressure, but the same type drills dressed and sharpened by my invention des-22 cribed herein goes through the same steel at a markedly accelerated pace yielding a very marked decrease in heat 23 build up.

For example I have sharpened a 1/16 inch diameter . 26 drill and then repeatedly tested it by drilling through a 1/4 inch plate of hard steel. The thread which resulted from such 28 drillings came out in a continuous spiral indicating that the drill was accurately and precisely center ground, and with 31 equal and well balanced cutting lips.

: -18-1~ This invention is a low cost device that will 2i easily and accurately sharpen drills from l/16 inch diameter 3 to over three inches in diameter with ideal geometry. I
4 know of no ordinary commercial or home shop machine which will accomplish this as satisfactorily, considering cost, 6 simplicity, precision attained, versatility in drill size 7 accommodation and portability as a group of factors.
9 A person skilled in the art having the benefit of the teachings of this disclosure will perceive that various 11 equivalent embodiments may be employed. It will be appreciated 12 that the preferred embodiment of my invention herein shown 13 and described can be subjected to numerous variations and 14 modifications which do not depart from the underlying prin-ciples of the invention. I therefore desire to include within 16 the scope of this invention all such variations and modifica-17 tions by which substantially the results of my invention may 18 be obtained through the use of substantially the same or 19 equivalent means. The invention is therefore to be limited Z only by the a ~omDanying claims.

24~

~2 . , . ...
. ' . . - ' . ~ . ~
.

Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for grinding twist drills and the like for use in cooperation with a grinding wheel apparatus comprising:
Drill locking means comprising a fence, a bed adjacent said fence, a finger, carried by said bed, which has an inclined plane coming to a point close to but not touching said fence, said inclined plane adapted to engage the trailing edge of the flute of a drill to be sharpened, and Longitudinal drill positioning means.

2. The device of Claim 1 wherein said finger approaches to from 1/64 inch to 3/64 inch clearance of said stop member.

3. The device of Claim 1 wherein said fence and said bed join at an angle and said finger approaches the apex of the angle.

4. The device of Claim 3 wherein said finger is integral with said bed.

5. The device of Claim 4 wherein said finger is bevelled at its point between the finger and said bed to form an auxiliary inclined plane.

6. The device of Claim 1 wherein said fence and bed comprise in combination an angular trough.

7. The device of Claim 6 wherein said angular trough has a bed and fence comprising sides meeting at about 90°.

8. The device of Claim 1 wherein said drill positioning means comprises a block slideably disposed in said trough, a bridge slideably disposed on the sides of said trough, and a set screw disposed in said bridge and bearing on said block.

9. The device of Claim 1 wherein the clearance between said point and said fence is about 1/32 inch.

10. The device of Claim 6 wherein the clearance between said point and the inner apex of said angular trough is about l/32 inch.

11. The device of Claim 1 wherein said finger has a slight separation at its point from said support bed.

12. The device of Claim 1 wherein said finger is disposed on said support to engage the trailing edge of the flute of the drill near its point.

13. The device of Claim 1 with the addition of support means upon which said drill locking means removeably rests.

14. The device of Claim 1 wherein said finger is a separate piece attached to said bed and comprises an elongate body disposed normal to the axis of the drill as carried by said bed.

15. The device of Claim 13 wherein the support means is a trough shaped to receive said drill locking means.

16. The device of Claim 1 with the addition of a motor, a grinding wheel operatively attached to said motor, and means for supporting said drill locking means in operative relationship to said grinding wheel.

17. The device of Claim 1 with the addition of drill vibration damping means.

18. The device of Claim 15 with the addition of feed adjustment means for limiting the forward excursion of the feed trough to the wheel.

19. The device of Claim 18 wherein the feed adjustment means for limiting the forward excursion of the feed trough relative the support trough comprises a mounting block attached to one of said troughs, a set screw disposed in said block and bearing on said other trough, a tension bar tapped to receive said threaded bolt and disposed on the shank of said bolt adjacent to said block such that the tension bar may be rotated to bear against the block.

20. The device of Claim 1 wherein said inclined plane has a convex radius.