US 4,974,372 AGranted

Universal device for sharpening drill bits

OwnerVinit P. Chantalatinventor

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Abstract

A sharpening device for sharpening drill bits on the flat surface of an electric grinding wheel or on a flat surfaced sharpening stone. The device includes a vise type drill bit holder which can accommodate various sizes of drill bits, the vise type holder having a slotted and angled set of jaws for positioning the drill bit at the correct grinding angle to the grinding surface. The holder is supported by handles such that the holder can be manually swivelled during a grinding process. A calibrated gauge for adjusting the protrusion of the drill bit from the holder is provided to obtain the correct lip angles. The sharpening device includes threads on the spindle about which the sharpening device rotates so that the drill bit moves sideways parallel to the grinding surface during grinding to prevent excessive wear in one spot on the grinding surface to thereby redress the grinding surface. Alternate means of supporting the holder are available including manually holding the device.

Claims17

Dependent claims

A drill bit sharpener for sharpening a drill bit against an abrasive sharpening surface, comprising:

drill holder means for holding said drill bit at a lip angle with respect to the sharpening surface so that the cutting lip edge of said drill bit is parallel to said sharpening surface;
swivel means for swiveling the drill holder means about a swivel axis, which swivel axis is parallel to said sharpening surface so that a relief angle is cut by said sharpening surface in said drill bit as said drill holder means swivels about said swivel axis;
means for controlling the protrusion of said drill bit from said means for holding so that a predetermined relief angle is cut in said drill bit by said sharpening surface;
wherein the means for controlling protrusion of said drill bit includes means for setting the protrusion of said drill bit to a precise length (PL) as equivalently determined by the equation ##EQU4## DEFINITIONS:
Where ##EQU5## R.A.=Relief angle;
r=Drill bit radius equal to 1/2 of the diameter of drill;
C=Distance between the drill axis and the swivel axis;
D=Distance between the swivel axis and the grinding plane;
.gamma.=The angle that the drill axis declines from swivel axis which is equal to half of the lip angle or point angle of said drill bit;
S=The lip land angle;
PL=The distance between the drill bit lip and the swivel axis where ##EQU6##

8 more elements

A method of sharpening a drill bit against an abrasive surface, comprising the steps of:

holding said drill bit with a drill bit holder at a lip angle with respect to the sharpening surface so that the cutting lip edge of said drill bit is parallel to said sharpening surface;
using a handle assembly for rotatably supporting said drill bit holder swiveling the drill bit about a swiveling axis, which swiveling axis is parallel to said sharpening surface so that a relief angle is cut by said sharpening surface in said drill bit as said drill holder means swivels about said swiveling axis;
controlling the protrusion of said drill bit from said drill bit holder so that a predetermined relief angle is cut in said drill bit by said sharpening surface as said drill bit is swivelled about said swiveling axis;
wherein the step of controlling the protrusion of said drill bit includes the step of setting the protrusion of said drill bit to a precise length PL as equivalently determined by the equation:
##EQU7## DEFINITIONS:
Where ##EQU8## R.A.=Relief Angle r=drill bit radius equal to 1/2 of the diameter of drill
C=Distance between drill axis and the swivel axis
D=Distance between the swivel axis and the grinding plane, .gamma.=The angle that the drill axis declines from swivel axis which is equal to half of the lip angle, or point angle of said drill bit,
S=The lip land angle,
PL=The distance between the drill bit lip and the swivel axis, where ##EQU9##

7 more elements

Dependencies are inferred from the claim text.