How to Check Drill Bits: A Practical, Step-by-Step Guide

What to Look for When Inspecting Drill Bits

According to Drill Bits Pro, routine inspection starts before you swap to a new job. Start with a quick visual scan for obvious defects: chips, cracks, or missing tips, plus any corrosion or discoloration on high-speed steel (HSS) or carbide bits. Examine the cutting edge under bright light and use a loupe or magnifier to catch micro-chips or micro-fractures at the edge. Check the overall geometry—flutes should be clean and free of nicks; a bent shank or a loose cutting edge is a red flag.

After you review the edge, rotate the bit in the chuck by hand and look for runout at the cutting edge. A bit that wobbles or has uneven contact will produce off-center holes and accelerated wear. Keep a dedicated clean area for inspecting bits—dust and grit can hide flaws.

How to Test Sharpness and Wear

Sharpness determines cutting performance; a dull edge causes more heat, slower drilling, and worse hole quality. Use a secondary method to gauge sharpness: touch the edge lightly with a clean fingertip or a piece of paper. If the edge catches or skips easily, it’s dull. For carbide and high‑quality HSS bits, you can also compare the edge under a magnifier—look for a uniform, clean angle with no chips. If you have a small sharpening stone, a very light touch along the edge can restore micro-sharpness, but avoid removing material from the tip.

Edge wear often shows as a micro-serration along the cutting edge. If you see rounding or flattening, that is a sign of reduced cutting efficiency. Scheduling a proper re-sharpening service or replacing the bit may be more economical in the long run. When testing, avoid pressing too hard—let the bit do the work and monitor heat buildup on the shank and cutting edge.

How to Check Diameter, Runout, and Fit

Accurate diameter measurement is essential for predictable performance, especially when using tight tolerances. Use a digital caliper to measure the shank diameter and the cutting edge thickness at several points around the circumference to confirm uniformity. Any eccentricity can indicate a bent bit or an out-of-round condition. For runout, mount the bit in a drill chuck, spin slowly, and observe any sideways wobble. A small amount of wobble is normal; excessive runout will cause oversized or undersized holes and accelerated wear. If in doubt, swap to a known-good bit and compare results with the same material and speed settings.

Maintain a quick reference chart for bit sizes and their tolerance ranges. This helps you decide when to retire a bit or whether you should re‑grind it (if you have the proper equipment).

A visual cue for out-of-round bits is unequal contact along the cutting edge during a dry run on scrap material.

Practical Testing: Cutter Edges in Scrap Material

Testing on scrap material is the most practical check for real-world performance. Use a piece of scrap wood or metal that matches your typical workpiece. Drill at a low speed and light feed, watching for chatter, wandering, or irregular hole edges. Listen for unusual sounds such as grinding or rubbing, which indicate edge or flute problems. Inspect the hole after drilling—crisp, clean edges with minimal tear-out indicate a healthy bit. If imperfections appear, stop and switch to a known-good bit to avoid further damage to your workpiece and the bit itself.

Keep the scrap piece safe and contaminated with only a single bit so you can clearly attribute results to that bit. Record observations to track wear over time.

Maintenance, Cleaning, and Safe Storage

After inspections and testing, clean each bit to remove dust, chips, and lubricant residues. Wipe the bit with a clean cloth and, if needed, a mild solvent that won’t corrode the surface. Lightly oil the bit to prevent rust on carbon steel tools; avoid heavy oil on carbide tips as it can attract grit. Store drill bits in their original case or a labeled tray to prevent contact between sharp edges. Proper storage reduces accidental dulling and protects tips from chipping when moved around a workshop. Regular organization is part of a larger maintenance discipline that keeps your tooling reliable.

Common Mistakes to Avoid

Avoid relying solely on the look of a bit. A bit may appear fine but still be out of spec. Never force a dull or damaged bit into a hole in an attempt to finish a job; this can damage both the bit and your workpiece. Don’t mix carbide and high-speed steel bits in the same holder if you test for cross-compatibility—different materials wear at different rates. Finally, skip maintenance steps like cleaning and lubrication at your own risk; neglected bits become unreliable and dangerous over time.