Most people throw away dull drill bits and buy new ones. That works for the cheap bulk sets, but quality drill bits — cobalt, TiN-coated, brad-point, and specialty bits — are expensive enough to justify sharpening. A dull twist bit that smokes, wanders, and produces rough holes takes 60 seconds to restore on a bench grinder or dedicated sharpening jig. The difference in performance is immediate: the bit bites into the material, spirals out clean chips, and drills a hole in half the time.

Drill Bit Sharpening

How to Tell a Bit Is Dull

A sharp drill bit cuts. A dull one rubs. The symptoms are obvious once you know what to look for:

Heat. The bit gets hot to the touch within seconds of drilling. Sharp bits stay cool because they are removing material efficiently. Dull bits generate friction heat that discolors the bit (turns it blue or straw-colored) and burns the workpiece.

Wandering. The bit skates across the surface instead of biting in at the center point. A sharp bit self-centers because the chisel point (the small edge at the very tip) digs into the material. A dull chisel point cannot penetrate and the bit drifts.

Rough holes. The hole edges are torn, splintered, or oversized. Sharp bits produce clean, round holes with smooth walls.

Smoke or burning smell. Especially in wood. The friction from a dull bit chars the wood fiber instead of cutting it.

Requires excessive pressure. You find yourself leaning on the drill to make progress. A sharp bit in wood requires minimal pressure — the flute geometry pulls the bit into the material.

Twist Bit Anatomy

Understanding the cutting geometry helps you sharpen correctly:

Lip (cutting edge): The two angled edges at the tip that do the actual cutting. They must be equal in length and at equal angles to the bit axis. Unequal lips produce oversized holes because one lip cuts deeper than the other.

Lip angle: The angle between each lip and the bit axis. Standard twist bits have a 118-degree included angle (59 degrees per side). Split-point bits have a 135-degree angle for better self-centering. For general sharpening at home, 118 degrees is the target.

Lip relief (clearance angle): A slight angle behind the cutting lip that allows the lip to bite into the material instead of sliding on a flat surface. Without adequate relief, the bit rubs instead of cutting. The relief angle should be 7 to 12 degrees.

Chisel point: The small flat edge at the center where the two lips meet. It does not cut — it pushes material aside. A sharp bit has a small, centered chisel point.

Method 1: Bench Grinder Freehand

This is the traditional method and takes practice to master. Once you get the feel, you can touch up a bit in 30 seconds.

Set up the bench grinder with a fine (80 to 120 grit) aluminum oxide wheel. Dress the wheel flat if it is grooved or uneven.
Hold the bit between your thumb and index finger with the lip you are grinding facing straight up.
Present the bit to the wheel at approximately 59 degrees to the grinding face (this creates the 118-degree included angle).
Lightly touch the bit to the wheel and simultaneously rotate the bit clockwise about 15 to 20 degrees while pulling the shank slightly downward. This single coordinated motion grinds both the lip angle and the relief angle in one pass.
Check the lip. Then rotate the bit 180 degrees and grind the second lip to match.
Check that both lips are the same length by rolling the bit on a flat surface and eyeballing the tip. If one lip is longer, the bit drills oversized holes.

Practice on junk bits. Buy a bag of cheap twist bits and grind them until the motion feels natural. It takes about 20 bits before the technique clicks.

Method 2: Drill Bit Sharpening Jig

Jigs remove the guesswork by holding the bit at the correct angle and presenting it to the grinder in a controlled motion.

Drill Doctor 750X ($100 to $130): The most popular dedicated drill bit sharpener. It grinds both the lip angle and a split point on bits from 3/32 to 3/4 inch. Setup takes 5 minutes the first time, then each bit sharpens in 30 seconds. The Drill Doctor is not perfect — it can leave a slightly rough finish on the lip — but it produces a functional edge that any homeowner can achieve consistently.

General Tools 825 ($15 to $25): A simple jig that holds the bit at 59 degrees against a bench grinder wheel. You rotate the bit by hand, but the angle is fixed. Less precise than the Drill Doctor but works for basic bits.

Veritas Drill Bit Sharpening Jig ($40): Holds the bit at the correct angle for honing on a diamond plate or sharpening stone. Produces excellent results but takes longer per bit.

For a home workshop with dozens of bits to maintain, the Drill Doctor pays for itself quickly. For occasional sharpening of a few bits, a freehand technique or the General Tools jig is sufficient.

Sharpening Brad-Point Bits

Brad-point (wood) bits have a center spur and two cutting lips with outer spurs. They require careful sharpening that preserves the geometry:

Hone the cutting lips on the flat face only using a fine diamond file or slip stone. Never grind the outside (angled) face — this changes the lip angle and diameter.
Touch up the center spur point with a fine needle file if it is blunted. The center spur must be the highest point for accurate centering.
Sharpen the outer spurs on the inside face only, using a fine triangular file. Maintain the original angle.

Brad-point bits are harder to sharpen than twist bits because of the multiple cutting surfaces. If the geometry is badly damaged, replacement ($3 to $5 per bit for quality brad points) is often faster.

Sharpening Spade Bits

Spade bits are the easiest to sharpen because the cutting geometry is simple:

Clamp the bit in a vise
File the cutting edges on each wing with a flat file, maintaining the original angle (roughly 10 degrees of relief)
File both wings equally to keep the center spur centered
File the center spur to a sharp point if it is blunted

A spade bit touchup takes 2 minutes with a fine mill file. Do this every time the bit starts burning wood instead of cutting it.

Sharpening Forstner Bits

Forstner bits have a center spur, a rim cutter, and inner cutting lips:

Hone the inner cutting lips on the flat face with a diamond paddle
Hone the rim cutter on the inside only with a round slip stone or fine half-round file
Touch up the center spur with a fine file

Forstner bits are precision tools ($8 to $20 each for quality bits). If the rim is badly chipped, send it to a professional sharpening service.

Storage After Sharpening

Store sharpened bits in a drill bit index (the flip-open cases with labeled holes) or a block of drilled hardwood. Loose bits in a drawer bang against each other and dull the cutting edges you just restored. Divide bits by type: twist bits in one index, brad-point in another, spade bits on a ring or in a pouch.

Bottom Line

A 30-second touchup on a bench grinder restores a twist bit to cutting condition. Learn the freehand technique on junk bits, or buy a Drill Doctor for consistent results. Sharpen brad-point and spade bits with hand files. The habit of sharpening instead of discarding saves money, reduces waste, and means every hole you drill is clean, round, and on-center. Keep a small file at the drill press and touch up bits the moment they start burning.