Note: Descriptions are shown in the official language in which they were submitted.
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B~C:~GROUNV O~ IE INV:I'NTION
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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
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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.
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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
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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.
12
13 It is an object of this invention to overcome the
14 disadvantages of the prior art devices.
16 BRIEF DESCRIPTION OF THE INVENTION
17
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.
28
?9 Considered in another aspect the drill locking
31 means is a feed trough or drill carriage having two sides
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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.
28
2 To precisely position the drill, simplified longi-
32 tudinal drill positioning means are provided. These may be
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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.
17
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
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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.
13
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.
19
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.
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2 DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
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;
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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
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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.
21
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.
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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.
14
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.
27
28 The finger 41 is a very important element of this
29 invention. The finger has two parts serving differing sizes
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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.
23
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.
29
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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.
11
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
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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.
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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.
16
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.
234
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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
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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.
1 1
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
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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.
16
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.
24
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.
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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.
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