How to Sharpen a Drill Bit: Angles and Methods

Sharpen a twist drill bit by regrinding both cutting lips to the same angle, 118° for general use or 135° for hard metals, with a small clearance angle behind each lip so the edge can bite. Use a bench grinder with a steady hand, or a drill bit sharpener for repeatable results. Coated, carbide and masonry bits are not worth sharpening by hand, and a bit that is chipped or bent is better replaced.

Signs a bit is dull

• It needs heavy pressure to cut.
• It squeals, smokes or burns the hole.
• It makes dust or powder in place of curled shavings.
• The tip is rounded, chipped or has turned blue from heat.

The angles that matter

Angle	Typical value	What it does
Point angle	118° for general use, 135° for hard metals	The angle between the two cutting lips
Lip clearance (relief)	About 10° to 15°	The edge sits slightly higher than the surface behind it, so the lip can cut
Chisel edge	Centered, short	The point at the tip; a split point shortens it and stops the bit from wandering

A 135° point with a split tip starts without walking and suits stainless and other hard metals, which is why bits for those jobs use it; see best drill bits for stainless steel. A 118° point is the standard for wood, plastic and mild steel.

How to sharpen a bit on a bench grinder

1. Wear safety glasses and keep a cup of water near. Never grind the bit until it turns blue; heat softens the steel.
2. Hold the bit near the tip with one hand and near the shank with the other, with a lip lying flat against the wheel.
3. Set the angle by eye against the face of the wheel (59° from the bit’s axis gives a 118° point).
4. Touch the lip to the wheel and lower the shank slightly as you grind, so the relief falls away behind the lip. Take light passes.
5. Rotate the bit half a turn and grind the other lip the same amount.
6. Check that the two lips are the same length and angle by looking down the bit from the tip. Uneven lips make an oversized, off-center hole.
7. Cool the bit in water between passes.

A drill bit sharpener or a sharpening jig holds the angle for you and is the easier route if you sharpen often. A cheaper option for light touch-up is a fine diamond file along each lip.

When to replace instead

Replace the bit when:

• the flutes are cracked or the tip is chipped;
• it is bent or the shank is worn;
• it is a small bit, where a new bit costs less than the time spent;
• it is a carbide-tipped or masonry bit, which needs a diamond wheel.

Match bit and material to avoid dulling in the first place. Best drill bits for metal covers coatings and cobalt, and hardened steel drill bits covers when you need carbide or cobalt. Use cutting oil on steel and a slow speed from the drill speed calculator.