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A worn drill bit is not just slower. It can wander across a surface, make an oversized hole, overheat, or snap under pressure. The right time to replace one depends on the bit type, the material, and whether the job needs a clean, accurate hole. A quick inspection and a short test hole can usually tell you whether a bit is still usable.
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Signs a drill bit is worn
Look at the cutting edges under good light. On a standard twist bit, the two lips at the tip should meet cleanly at the center and look reasonably even. Rounded, chipped, or uneven edges are signs that the bit has lost its bite. A shiny flat spot on a cutting edge can mean it has rubbed against the material instead of cutting it.
Other clues show up during drilling. A sharp bit makes a steady stream of chips and advances with moderate pressure. A dull one squeals, polishes the hole wall, produces fine dust instead of chips in wood or metal, or takes noticeably longer to cut. If you need to push hard, stop and inspect the bit rather than leaning harder on the drill. Extra force can overheat the bit, damage the workpiece, or twist the bit in the chuck.
Check the shank too. Replace a bit with a bent shank, deep gouges, cracks, or a badly rounded drive end. A bit that wobbles in the chuck can make an oversized hole even if its cutting edges are sharp. First reseat it in the chuck and tighten securely; if it still runs out of true, retire it.
Test the bit before discarding it
Clean off packed dust or metal chips, then drill a small test hole in scrap of the same material. Use the correct speed and mode: ordinary drilling for wood or metal, and hammer mode only for a masonry bit in masonry. Start slowly enough to keep the tip from wandering, then let the bit cut without excessive pressure.
Compare the test hole with one made by a known-good bit. If the worn bit takes roughly twice as long, needs much more force, leaves a ragged opening, or heats quickly, replacement or sharpening is sensible. Do not touch a hot bit with bare fingers. Let it cool before inspection, and stop immediately if you see smoke, discoloration, or a burning smell.
Before blaming the bit, check the setup. A low battery, wrong drill speed, slipping chuck, or unsuitable bit can mimic wear. For example, using a wood bit on concrete will not become effective by pressing harder. Match the bit to the material and consult the drill and bit instructions when in doubt.
What wear looks like by bit type
| Bit type | Wear or failure signs | Replace when |
|---|---|---|
| Twist bit for wood or metal | Rounded lips, chipped tip, bent shank, or frequent wandering | It struggles in a test hole after cleaning and correct setup |
| Masonry bit | Blunt or chipped carbide tip; slow progress and excess heat | The tip is damaged or it no longer cuts masonry at a reasonable pace |
| Spade or hole-saw bit | Blunt outer spurs, chipped teeth, or a bent pilot bit | The cut tears out badly or stalls despite a clear cutting path |
| Driver bit | Rounded, chipped, or twisted tip that slips from the fastener | It cams out repeatedly in a matching, undamaged screw head |
Masonry bits deserve particular attention when drilling for wall anchors. A blunt carbide tip can leave a hole that is too wide or irregular, so the plug spins instead of gripping. A hole that is too shallow can also prevent the anchor from seating. Follow the anchor’s stated hole diameter and depth; do not compensate for a loose hole by forcing in a larger anchor unless its instructions allow it.
Sharpen or replace?
Sharpening can extend the life of suitable twist bits, but the two cutting lips need to remain balanced and meet at the right point angle. An uneven hand-sharpened bit may cut off-center and make an oversized hole. If you drill often and have a sharpening guide or a service that can restore the geometry, sharpening quality high-speed-steel bits can be worthwhile.
For occasional home use, replacing a small, inexpensive bit is often the simpler choice. Carbide-tipped masonry bits and specialty bits are harder to restore accurately with basic tools. Replace them if the carbide is cracked, missing, or badly chipped. A cheap bit is fine for a few holes in softwood, but a better-quality bit is a sensible purchase for repeated work in steel, hardwood, or masonry.
When replacing a general-purpose set, compare the materials and sizes you actually use rather than buying the largest assortment. A high-speed-steel drill bit set covers many basic wood and metal jobs; coated versions can help with heat and wear, but a coating does not make a dull or unsuitable bit cut well. For wall holes, choose a carbide-tipped masonry bit sized to the anchor manufacturer’s specification.
Make replacement bits last longer
Use a steady speed and let the cutting edges do the work. For larger holes in metal, reduce speed; if the bit maker allows it, use cutting fluid to limit heat. In wood, withdraw the bit occasionally to clear chips, especially in deep holes. With a hammer drill, use an appropriate masonry bit and switch off hammer action for materials that can crack or splinter. An impact driver is for driving compatible fasteners, not for drilling ordinary round-shank bits unless the accessory is explicitly rated for impact use.
Store bits dry and separated so cutting edges do not knock against one another. Mark damaged bits for disposal rather than putting them back in the case. If a hole must be accurate—such as for a close-fitting dowel or a wall anchor—use a sharp bit even if an older one still manages rough work. Keep a worn bit only for low-risk tasks such as opening a rough clearance hole, where accuracy and finish do not matter.