How to Sharpen Drill Bits: Restore Your Dull Bits to Like-New Condition

How to Sharpen Drill Bits

A dull drill bit is one of the most frustrating things in any workshop. It burns the wood, skates on metal, overheats, and produces ragged holes. The good news is that sharpening a drill bit takes only a few minutes and can restore a worn bit to near-factory performance. Here’s everything you need to know.

Why Drill Bits Go Dull

Drill bits lose their edge through friction and heat. Each time the cutting lips (the two angled edges at the tip) bite into material, they wear down slightly. Hard materials like steel, masonry, and hardwood accelerate this process. Signs of a dull bit include: needing to apply excessive pressure, the bit wandering on the surface, squealing or burning smells, and holes with rough, torn edges.

What You’ll Need

Before you start, gather the right tools:

• Bench grinder (the most common method) or a drill bit sharpening jig
• Angle grinder or rotary tool (Dremel) as alternatives
• Safety glasses — always
• A cup of water for cooling the bit
• A marker or paint pen (optional, but helpful for beginners)

Understanding Drill Bit Geometry

The standard twist drill bit has two main angles you need to preserve when sharpening:

Point angle: Most general-purpose bits have a 118° included angle at the tip (59° on each side). Bits for harder materials like stainless steel may use 135°. This angle is what you’re recreating when you grind.

Relief angle (clearance angle): Behind each cutting lip, the metal slopes away (typically 8–12°). This relief is critical — without it, only the very edge cuts; the rest of the bit drags and burns. Many beginner sharpening mistakes destroy this clearance.

Chisel edge: The very center of the bit where the two lips meet. It doesn’t actually cut — it scrapes. A sharp chisel edge is narrow and centered.

Method 1: Bench Grinder (Most Common)

This is the preferred method for most home workshops. It takes practice, but once you get the feel, it’s fast and reliable.

Step 1 — Inspect the bit. Hold it under a bright light and look at the tip. The two cutting lips should be equal in length and meet at the center. If one lip is longer, the bit will drill an oversized, off-center hole.

Step 2 — Mark the cutting lips. Use a marker to color both cutting lips. This lets you see exactly where the grinder is removing metal after each pass.

Step 3 — Set your angle. Rest the bit on the grinder’s tool rest at roughly 59° to the wheel face (for a standard 118° bit). Your grip matters here: hold the bit near the tip with your dominant hand’s index finger and thumb, and support the shank with your other hand.

Step 4 — Grind the first cutting lip. Bring the cutting lip flat against the wheel. As you grind, simultaneously rotate the shank downward while applying light pressure. This rotation is what creates the relief angle behind the lip. Grind for 2–3 seconds, then dip the bit in water to cool it.

Step 5 — Check your work. Look at the cutting lip — the marker should be worn away evenly. The face behind the lip should slope away noticeably (that’s your relief angle). If the face is flat, you haven’t rotated enough.

Step 6 — Grind the second lip. Rotate the bit 180° and repeat, trying to match the first side exactly in length and angle.

Step 7 — Check symmetry. Both cutting lips must be the same length and meet at the center of the bit. A drill bit gauge or angle gauge makes this easy, but you can also eyeball it under magnification. Even a slight difference causes the bit to drill oversize holes and wobble.

Step 8 — Test it. Drill into a piece of scrap wood or metal. A properly sharpened bit will cut smoothly with light pressure, producing clean, uniform chips and no burning.

Method 2: Drill Bit Sharpening Jigs

If the freehand bench grinder technique feels intimidating, a sharpening jig (such as the Drill Doctor or similar) takes the guesswork out of the angles. You simply insert the bit, set the size, and follow the device’s guided motion. Jigs are excellent for beginners and for sharpening small bits (under 3mm), which are nearly impossible to sharpen freehand.

Method 3: Rotary Tool or Angle Grinder

For field repairs or when a bench grinder isn’t available, a Dremel with a grinding stone or a small angle grinder can work. This method demands a very steady hand and good lighting. Use the same principle: grind the cutting lip at 59°, rotate slightly to create relief, and work both sides evenly.

Tips for Success

Cool frequently. Heat is the enemy. If the bit tip turns blue or brown, you’ve overheated the steel and softened it. Dip in water every few seconds.

Little by little. Remove only as much metal as necessary. Aggressive grinding removes material quickly but makes it harder to keep the geometry correct.

Sharpen often. Bits are much easier to sharpen before they’re completely ruined. A slightly worn bit needs only a touch-up; a badly damaged one may be beyond saving.

Don’t neglect small bits. Tiny bits (1–3mm) are cheap enough to replace, but if you want to sharpen them, a jig or a small diamond file is the practical approach — freehand grinding at that scale is extremely difficult.

Masonry bits are different. Carbide-tipped masonry bits require a diamond grinding wheel or a specialized carbide grinder. The technique is similar, but standard abrasive wheels won’t touch carbide effectively.

When to Replace Instead of Sharpen

Some bits are beyond saving. If the tip has broken off, if the flutes (the spiral grooves) are packed or damaged, or if the bit has been overheated so many times that the steel has lost its temper, buy a new one. Good quality HSS (high-speed steel) bits are inexpensive, and no amount of sharpening will restore a fundamentally compromised bit.

Final Word

Sharpening drill bits is a skill that pays for itself quickly. A sharp bit cuts faster, produces cleaner holes, puts less strain on your drill motor, and is safer to use. With a bench grinder and 10 minutes of practice, you’ll be able to keep your entire drill bit set in top condition — and you’ll never have to fight a dull bit through a piece of hardwood again.