Craftsman refers to its drill bit sharpening jig as a drill grinding attachment. The jig is used in conjunction with a bench grinder to grind the correct angles on drill bits to be sharpened. The drill grinding attachment can be used to sharpen drill bits up to 3/4-inch in diameter or grind a new tip on a broken bit. The sharpening attachment can be used against the normal grinding edge of a grinder wheel. If you want to grind on the side of the wheel, a grinder wheel specifically designed for side grinding must be used.
Things You'll Need
- Bench-mounted shop grinder
- Wing nut
Install the drill grinding attachment onto your grinder bench. Attach the jig to the bench with a single bolt inserted 2-1/4 inches in front of the grinder wheel's grinding surface and through the bench. Thread a wing nut onto the bolt so the nut can be loosened. The bolt goes through the slot in the bottom of the jig so it can be adjusted toward or away from the grinder. Once the jig is in position, tighten the wing nut to hold the sharpening jig securely to the bench.
Set the grind angle on the jig and tighten the adjusting nut. A 59-degree angle can be used for general purposes. A steeper angle, up to 88 degrees, is better for drilling hard substances. A lesser angle of 49 degrees can be used for softer materials, such as copper and plastic.
Place the drill bit to be sharpened into the bit trough, with the end equal to the bit's diameter sticking out of the front of the trough. Adjust the rear slide bracket snug against the back end of the bit.
Adjust the lip rest of the jig up or down until it catches the cutting edge of the drill bit. The lip rest is a piece of metal on the front of the sharpening jig held in place by two small screws. Rotate the drill bit until the drill lip is against the lip rest to hold the bit in the proper position to grind. Finger-tighten the clip at the top of the jig to hold the bit in position.
Adjust the entire jig by loosening the wing nut and bolt that hold the jig to the bench and sliding the entire assembly until the drill bit almost touches the grinder wheel then snugly tighten the wing nut. The jig pivots side to side and sharpens the bit as it passes across the wheel. The screws on the nameplate adjust the friction of the pivot.
Turn on the grinder and sharpen one side of the bit with the side-to-side pivot motion. The knurled feed nut at the back of the jig will push the bit forward in small increments so you can grind a smooth surface on the bit point. A 1/8-turn of the feed nut will move the bit six-thousandths -- 0.006 -- of an inch forward.
Repeat the grinding process for the other half of the drill bit point by loosening the bit clamp and feed nut then rotating it 1/2-turn so the other lip of the bit is against the lip rest. Grind off the same amount of material on the other side.
Tips & Warnings
- After grinding, visually inspect the drill bit tip for an even grind with the two sides proportional.
- These steps are for the most typical bit shape. You may need to adjust your technique for bits with different cutting end profiles.
- Use a couple of older, less important bits for your first attempts at sharpening. Use those bits to develop your technique for using the jig.
- Always used safety goggles or a face shield, along with the grinder shield, when using the drill grinding attachment.