How to Sharpen Drill Bits: Extend Their Life

Blunt drill bits don't just work poorly - they damage material, overheat, and make you work harder. Learning to sharpen them saves money and improves your work. Here's how.

When to Sharpen

Signs your bit needs attention:

• Takes more pressure to cut
• Creates more heat than usual
• Produces fine powder instead of curled chips
• Wanders or squeals when starting
• Visible wear on the cutting edges

Don't wait until bits are useless. Regular light sharpening maintains performance.

Understanding Drill Bit Geometry

Before sharpening, understand what you're maintaining:

Point Angle

The angle at the tip. Standard is 118° for general purpose, 135° for harder materials. You need to maintain this angle.

Lip Clearance Angle

The angle behind the cutting edge. Typically 8-12°. Too little and the bit won't cut; too much and the edge is weak.

Chisel Edge

The flat point at the very tip. Should be centered. An off-center chisel makes the bit wander.

Sharpening by Hand

Equipment

• Bench grinder with fine wheel (60-80 grit)
• Safety glasses
• Container of water for cooling
• Good lighting

Process

1. Hold the bit at the correct point angle against the wheel (roughly 59° from horizontal for a 118° point)
2. Position one cutting lip horizontal
3. Touch the lip to the wheel and rotate the bit clockwise while pushing slightly in
4. This creates the lip clearance angle
5. Dip in water frequently to prevent overheating
6. Rotate 180° and repeat for the other lip
7. Compare both lips - they should be identical length and angle

The Key Points

• Keep both lips equal length
• Maintain consistent point angle
• Create adequate clearance behind the cutting edge
• Keep the bit cool (blue colour means overheated and softened)

Using a Drill Bit Sharpener

Dedicated sharpeners take the guesswork out. They hold the bit at correct angles automatically.

Types

• Electric sharpeners - Motor-driven, consistent results, easy to use
• Grinding jigs - Attachments for bench grinders that hold bits at correct angles

For anyone doing regular sharpening, a dedicated sharpener is worth the investment. It produces consistent results faster than hand sharpening.

Which Bits to Sharpen

Worth Sharpening

• HSS (high-speed steel) bits - standard twist drills
• Quality bits that cost more to replace
• Larger diameter bits (more material to work with)

Not Worth Sharpening

• Very small bits (too fiddly, cheap to replace)
• Carbide-tipped masonry bits (need diamond wheel)
• Extremely worn or damaged bits
• Cheap bits that cost less than your time

Testing Your Work

After sharpening:

• Visual check - both lips should look identical
• Roll on flat surface - should spin evenly if lips are equal
• Test cut in scrap - should start easily and cut smoothly
• Check swarf - should produce curled chips, not dust

Common Mistakes

Overheating

Blue discolouration means you've drawn the temper. The steel is now soft and won't hold an edge. Light touches and frequent cooling prevent this.

Unequal Lips

One lip longer than the other makes the bit cut oversize and wander. Take your time and check often.

Wrong Clearance

No clearance = bit won't cut. Too much clearance = weak edge that chips. Aim for 8-12°.

Changing the Point Angle

Steeper angles (more pointed) are weaker. Flatter angles need more pressure. Maintain the original geometry.

Prevention

Bits last longer if you:

• Use correct speed for material
• Let the bit do the work (don't force)
• Clear chips regularly (especially in deep holes)
• Use cutting fluid on metal
• Store bits properly (not loose in a drawer)

Browse our drilling accessories for bits and sharpening tools.