US3553898A

US3553898A - Drill sharpening apparatus or the like

Info

Publication number: US3553898A
Application number: US717242A
Authority: US
Inventors: Alfred Nobile
Original assignee: Alfred Nobile
Current assignee: SERVICE PRECISION GRINDING COMPANY Inc A CORP OF NJ
Priority date: 1968-03-29
Filing date: 1968-03-29
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12

Abstract

IMPROVED DRILL SHARPENING APPARATUS IF DISCLOSED COMPRISING (1) A MOTOR HAVING A SHAFT, (2) A THIN WALLED TUBULAR GRINDSTONE MOUNTED BY ONE OF ITS ENDS TO THE SHAFT, (3) AND DRILL HOLDING APPARATUS FOR MOVING A DRILL ACROSS THE END WALL OF THE GRINDSTONE AND INTO ITS HOLLOW PORTION DURING A SHARPENING OPERATION.

Description

Jan. 12, 1971 A. NOBILE DRILL SHARPENING APPARATUS OR THELIKE Filed March 29, 1968 2 SheetsShee t 1 /N|/ENTOR By AL RED NOB/LE LU flbfi ATTORNEY Jan. 12, 1971 A. NOBILE 3,553,898

DRILL SHARPENING APPARATUS OR THE LIKE 2 Sheets-Sheet 2 Filed March 29, 1968 25 /22C/22A /22B F/G- 3 I g FIG. 46

' lNl/ENTOR By ell/M;

ATTORNEY AL FRED NOB/ LE United States Patent 3,553,898 DRILL SHARPENING APPARATUS OR THE LIKE Alfred Nobile, 3 Ledgewood Trail, Sparta, NJ. 07871 Filed Mar. 29, 1968, Ser. No. 717,242 Int. Cl. B24b 3/26, 9/00 US. CI. 51-73 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to drill sharpening apparatus and in particular to apparatus which permits drills of varying sizes to be sharpened with ease and precision.

With the present cost of drills, especially those of the larger sizes, it has become a commercial necessity that drills be resharpened, rather than replaced, as they become dull so that maximum service may be obtained therefrom for each dollar of investment. The present methods and equipment for sharpening drills on the job in machine shops and the like, is either unsatisfactory and unreliable, or bulky, complicated and expensive.

It is common practice to sharpen drills by hand with the aid of a grindstone. This method is most unsatisfactory since, due to the complicated considerations involved, it normally requires considerable skill and many years of experience for the art of sharpening drills by hand to be mastered. A novice or an apprentice is more likely to ruin a drill than he is to be able to sharpen it successfully.

Drill sharpening devices have been commercially available for many years. All such devices hold a drill against the side or periphery of a grindstone at a preset angle during the sharpening operation. These devices work reasonably well for the first few drills to be sharpened on a new stone. However, after a brief period of use, the stone takes a set (a groove is worn in its surface) and further sharpening operations cannot be satisfactorily accomplished until the stone is replaced or resurfaced.

BRIEF SUMMARY OF THE INVENTION It is therefore an object of the invention to provide improved drill sharpening apparatus.

It is a further object to provide improved drill sharpening apparatus in which the abrasive medium (the grinding wheel) is longer lived and need not be replaced or resurfaced as frequently as has been heretofore required.

In accordance with my invention, I provide a new and improved drill sharpening apparatus comprising (1) a motor, (2) a tubular configured, thin, walled, open ended, grindstone affixed to the motor shaft and rotated thereby, and (3) apparatus for holding a drill and moving it across the open end of the hollow stone. The drill is sharpened by the end area of the stone defined by the thickness between its outer and inner walls. The drill holding apparatus holds the drill at the required angle with respect to the end surface of the stone to maintain the desired cutting angle and clearance at the tip of the drill. After being mounted in the holding apparatus and prior to engaging the stone, the drill is adjacent the end portion of the outer wall of the stone.

During the sharpening operation, the drill is moved inwardly across the outer end of the stone, against and past the outer portion of the stone, and finally past the ice inner wall and into the hollowed center portion of the stone. The orientation of the drill with respect to the end portion of the stone imparts the desired cutting angle to the end of the drill. The engagement of the drill with the inner wall of the stone imparts the desired clearance to cutting surfaces of the drill. This latter clearance is provided by the curvature of the inner wall of the stone. Since the drill has two cutting edges, each drill to be sharpened is first moved past the stone to sharpen one edge; and is then rotated and moved past the stone again to sharpen the other edge.

My invention is an improvement over the prior art arrangements in that the entire surface defined by the wall thickness at the end portion of the stone is used in the sharpening of each drill, regardless of its size. This feature prevents the stone from being grooved and greatly extends its useful life.

These and other objects and features of my invention may be better understood from a reading of the following description taken in conjunction with the drawing in which:

FIG. 1 comprises a top overall view of apparatus embodying the invention.

FIG. 2 shows a leading end view of the drill holding apparatus taken along line 22 of FIG. 1.

FIG. 3 shows a top view of the apparatus of FIG. 3.

FIGS. 4A, 4B, and 4C illustrate the manner in which drills should be ground.

FIG. 5 shows an end view of the grinding wheel oriented with respect to a drill to be sharpened.

FIG. 6 illustrates a top view of a drill to be sharpened oriented with respect to a lower horizontal half section of the grinding stone.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a base 10, and a motor 11 having a shaft 12 upon which is fixably mounted] a tubular like hollow grindstone 13, whose open right end is adjacent a drill 14. Mounted upon base 10 is a pair of end members 16, and a pair of rails 17. Slidably afiixed to rails 17 is a motor base 18 for motor 11. The lower portion of motor base 18 is threaded to receive a threaded screw 19 having an end portion 20 which is rotatably mounted in left end member 16. A knob 21 is fixably attached to the end portion 20 of screw 19. The rotation of screw 19 and knob 21 causes the motor and its base 18 to slide to the left or right on rails 17. The slideable adjustment provided by screw 19 permits the end of stone 13 to be positioned to engage drill 14 with the correct pressure. As subsequently described in greater detail, drill 14 is held by apparatus 22 (comprising

elements

22A, 22B and 22C) which is mounted atop a base block 24. Rails 26 are fixably mounted to base 10 and permit base block 24 to slide atop base 1.0 in the manner show in FIGS. 1 and 6 thereby move the cutting end of drill 14 across the end of stone 13 and into the hollow portion during the drill sharpening operation. FIGS. 2 and 3 illustrate the drill holding apparatus in greater detail. Base block 24 has a hole drilled in upper surface to receive a vertical shaft 23 which is fixably held to base block 24 by set screw 25 (FIG. 2). Drill holder element 22C is drilled and tapped to receive a threaded screw 27 to whose right end is fixably attached an adjustment knob 28. Drill holder 22 further includes

members

22A and 22B which are separate from but which cooperate with member 22C to hold drill 14. Element 22A is triangular shaped as shown in FIG. 2 and is fixably attached to element 22B by screws 29 (FIG. 1). Element 22B is drilled to rotatably receive screw 27 which extends into the tapped portion of holder element 22C. A collar 30 is fixably attached to screw 27 and bears upon the left edge of member 22B (FIG. 2) so that the counterclockwise rotation of screw 27 by knob 28 causes

elements

22A and 22B to move to the right and further separate from holder 22C. Member 22B has drilled holes to fixably receive guide pins 31 (FIG. 3). Pins 31 slideably extend into cooperating holes in element 22C. Pins 31 maintain the proper orientation of element 22A with element 22C as knob 28 and screw 27 are rotated.

Holder element 22C is drilled to slideably receive shaft 23. Element 22C is initially adjustable about shaft 23 but may be fixably attached thereto by means of a set screw 33, (FIG. 3) in the left edge of element 22C. Element 22C is drilled to receive shaft 23 in such a manner that the upper surface and the right and left sides (FIG. 2) of holder 22 are offset from horizontal and vertical, respectively, by a predetermined angle in the manner shown on FIG. 2. Element 22C is further drilled and tapped to rotatably receive an adjusting screw 32 whose lower end bears against indexing holes (not shown) in the upper surface of base block 24. When initially adjusting the position of element 22C, screw 32 is rotated to fix the vertical separation of element 22C above block 24 while screw 33 is rotated and tightened after element 22 is rotated about shaft 23 so that the lower end of screw 32 engages the desired indexing hole in the upper surface of block 24.

A drill to be sharpened is inserted in the space between the wedged opening in the right side of holder 22C and the left edge of member 22A. The drill is rotated so that one of its cutting edges is parallel to the horizontal (FIG. 2), knob 28 is then rotated to move member 22A to the left to bear against the drill and fix its position and prevent its movement in the holder during the sharpening operation. Lower clamp 34A is drilled to rotatably receive screws 35. Upper clamp is drilled and tapped to receive screws 35. After the drill is rigidly clamped between

elements

22C and 22A, clamps 34A and 34B are positioned over and under the drill as shown in FIGS. 2 and 3. Screws 35 are then tightened so that clamps 34A and 34B rigidly press against the drill. The index stub 36 of clamp 34B bears against shelf 37 formed in member 22B,

After the drill is positioned in the holder 22 as described, base block is slid back and forth between rails 36 so that the cutting end of drill rubs against the end of stone 13 after the position of it and the motor are adjusted by knob 21. The back and forth travel of the drill with respect to the stone (along the path represented by the dotted line on FIG. 6) causes the end of the stone to sharpen the left cutting edge of the drill with proper clearance and cutting angle as subsequently described After the left cutting edge is sharpened, knob 28 is loosened to free drill 14 and permit it and clamps 34A and 34B to be rotated counterclockwise 180 (FIG. 2) so that the index stub bears against shelf 37 of member 22C. Knob 28 is then tightened to rigidly clamp the drill. Block 24 is once again moved back and forth between rails 26 to sharpen the other cutting surface of the drill. After the initial sharpening operation of each side, the operations may be repeated to obtain a finished cut.

As may be seen best from FIG. 6, the axis of the drill is offset from the radial axis of the stone. This angle of offset determines the cutting edge angle, which ideally may be 59 as shown on FIG. 4A. This angle may be adjusted as desired by loosening set screw 33, rotating holder about shaft 32 (FIG. 3) to a different position and then retightening the set screw.

The adjustment provided by screw 32 determines the vertical position of holder 22 (FIG. 2) and in turn determines the vertical position of the drill with respect to the axis of the stone as shown on FIG. 5. The vertical position of holder 22 in turn determines what is known as the clearance of each cutting surface of the drill. One cutting edge C and a trailing edge D of the drill is shown on FIGS. 4. For proper sharpening it is necessary that point A (lower end of the cutting edge) be above point B (lower end of trailing edge). The clearance angle is shown on FIG. 4A and is defined by the angle between the horizontal and a line drawn through points A and B.

The fact that point A is above point B provides clearance and prevents binding of the drill during a cutting operation. Clearance is also provided by virtue of the fact that the point A is further from the lengthwise axis of the drill than is point B. This provides a cutting surface that has a decreasing radial distance from the axis of the drill as a path on the surface extending from cutting edge C to trailing edge D is traversed.

As shown on FIG. 5, the higher the drill is with respect to the horizontal center plane of the stone, the smaller will be the clearance. If the drills center coincided with the center of the stone, points A and B would engage the stone in such a manner that an improper cut as shown on FIG. 4B would result, i.e. there would be no clearance at all.

When the drill is properly positioned below the center of the stone, points A and B engage the stone in such a manner that the distance between lines A and B (projections of the contact of points A and B with the stone) equals the amount that point B is below A on FIG. 4A.

If the drill were lowered an excessive amount below the center of the stone, the surface adjacent point B would be ground to excess and an excessive clearance would result as shown in FIG. 4C.

The angle that the top of holder 22 is canted above horizontal insures that all drills, regardless of their size, clamped between

members

22C and 22A will be so oriented with respect to the stone to provide the proper clearance angle.

The end of the stone in FIG. 6 is shown beveled in the manner that it would be after considerable use. However, initially the end of the stone may be entirely fiat and with respect to the axis of the stone. The drills will still be properly sharpened since the bevel is not a necessary part of the stone.

While the invention has been described with reference to drills, taps, reamers, and endmills, other such devices may also be ideally sharpened in a similar manner.

It is to be understood that the above described arrangements are but illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. Drill sharpening apparatus comprising a shaft, motor means for rotating said shaft, an open ended tubular grindstone one end of which is mounted to an end of said shaft and rotated thereby, a drill, and means for guiding the path of travel of the cutting end of said drill across and against the end portion of a wall of said stone and into the open ended hollow portion of said stone during a drill sharpening operation, said guiding means comprising means for adjusting the position of the cutting end of said drill with respect to the end of said stone for controlling the abrasive force exerted on said drill by said stone during said sharpening operation, said guiding means further comprising adjustable means for controlling the angle between the longitudinal axis of said drill and said shaft for determining the cutting angle on said drill during said sharpening operation.

2. The apparatus of claim 1 in which said guiding means further comprising adjustable means for controlling the distance between a line defined by the path of travel of the center of the cutting end of said drill and a plane parallel to said line and containing the longitudinal axis of said stone for determining the clearance angle formed on said drill during said sharpening operation.

3. Drill sharpening apparatus comprising a motor having a shaft, an open ended tubular grindstone, means for mounting one end of said stone to an end of said shaft whereby said stone is rotated about its longitudinal axis upon the operation of said motor, and means for urging a cutting end of said drill against and across a wall of said stone at its open end during a sharpening o eration, said means for urging comprises a pair of parallel coplanar spaced apart guide rails, and mounting means for said drill, said rails, being effective to control the path traversed by said drill across an end wall of said stone during said sharpening operation, said mounting means comprises a base block slideably positioned between said rails, a first shaft normal to a top surface of said block and a drill holder attached to an upper end of said shaft, said drill holder being effective to hold said drill at a predetermined height and angle with respect to said stone during (a) said sharpening operation as said block is moved in a path determined by said rails.

4. The apparatus of claim 3 in which said holder comprises a first member having a V shaped slot on one of its sides for receiving a drill to be sharpened, a matching V shaped member spaced apart from and parallel to said V slot and being adjustable adapted to enter said slot and bear against a drill therein, and means for controllably adjusting the distance between said V slot and said V member to fixably hold a drill during a sharpening operation.

5. The apparatus of claim 4 in combination with means for adjustably afiixing said holder with respect to said shaft to define the cutting angle formed on said drill during a sharpening operation.

6. The apparatus of claim 5 in combination with means for adjustably afiixing said holder with respect to said shaft to define the clearance angle formed on said drill during a sharpening operation.

7. The apparatus of claim 6 in combination with 'means for holding said drill in a first position while one cuting surface of said drill is sharpened, means for rotating said drill about its longitudinal axis, and means for holding said drill in said rotated position while a second cutting edge of said drill is sharpened.

8. The apparatus of claim 7 in combination with means for controlling the abrasive force exerted on said drill by said stone during said sharpening: operation.

References Cited UNITED STATES PATENTS 876,428 1/1908 Blessing 5173 2,305,230 12/1942 Allen 51-2l9 2,334,089 11/1943 Hallden 51-219X 2,512,888 6/1950 Douglas 51-73 OTHELL M. SIMPSON, Primary Examiner US. Cl. X.R. 51--219