The basics are pretty basic, but mastering it takes practice:
-1/4 inch drills are a nice size to learn on.
if you have put off learning for a long time, you likely have a box full of these waiting to practice on anyway.
-very small drills are that much more difficult to do.
-a magnifying lens like an Optivisor doesn't hurt one bit.
There are generally three essential requirements in twist drill sharpening:
1. Equal drill-point angles, which are usually 59 degrees each for a total of 118 degrees
2. Cutting lips of equal length
3. Correct clearance behind the cutting lips, which is approximately 8 to 12 degrees
A handyman's adjustable protractor can be used to check both the drill-point angle and the lengths of the cutting edge lips. The appropriate clearance behind the cutting lip can be determined by visual inspection. The resulting clearance angle is not critical as long as it is approximate 8 to 12 degrees.
Clearance must be provided all along the cutting lip. Little or no clearance prevents the cutting edge from producing a chip, and the drill will just not drill. The cutting edge will be held off the work. Too much clearance weakens the cutting edge because too much metal behind the edge is removed.
Grind all twist drills without overheating them. Keep their points cool enough so that you can touch them with your bare fingers. Making very light passes over the wheel can do this.
Freehand Sharpening
Even if you do not sharpen the twist perfectly, it will still cut wood, although the hole may be slightly oversize.
Begin by holding the bit on your forefinger, with its cutting lip horizontal and the axis of the drill at an angle of about 59 degrees.
The actual grinding process actually involves three distinct motions of the shank while the bit is held lightly against the wheel.
Note: The operator moves the shank of the bit left and downward while simultaneously rotating it from the cutting edge back.
The three motions are:
1 .To the left
2. In a clockwise rotation
3. Downward
