When to Stop Resharpening and Just Retire the Bit

Resharpening exists because most "dull" drill bits aren't actually dead — they're just dull. A WinsloMatic-ground regrind restores the cutting geometry to factory spec. Done correctly, a bit can be resharpened 5 to 8 times before it's genuinely worn out.

But some bits are done. Sending them in wastes money and delays the bits that deserve to be brought back.

THE HARD RULE: BODY LENGTH

Every resharpen removes material from the point. Eventually the drill gets too short to be useful. The practical minimum is roughly 50% of original flute length. Below that, chip clearance suffers and the bit can't reach full depth on most jobs. This is the clearest retirement criterion — when the bit is too short, it's retired.

You can track this by marking original length on a clipboard or simply keeping worn sets sorted by size and measuring once a year.

WORN FLUTES — NOT FIXABLE

The cutting edges are at the tip. The flutes are the helical channels that evacuate chips. Resharpening fixes the tip. It does nothing for worn flute lands — the outer margins where the drill contacts the hole wall.

A bit with worn margins will produce oversized, rough holes even after a perfect regrind. Signs of flute wear: shiny stripes on the outer diameter, scoring inside the hole, holes that run consistently oversize despite correct speeds and feeds.

Once the margins are worn through, the bit is retired.

CORE DAMAGE AND BENT BODIES

A drill bit that has been run into a hard spot, spun in a chuck, or fed too hard can develop a bent body or cracked core. You'll see this as a wobble under rotation (even with a good chuck) or visible deviation from straight when you sight down the flute.

These bits are done. No regrind fixes a bent body.

CHIPPED LANDS AND BROKEN CHISEL EDGES

If the point has been catastrophically chipped — not just dulled — the regrind removes material past the damage. For large chips, this can require removing significant length. If the remaining bit is already short, retirement makes more sense than taking another 1/4" off the tip.

Send the bit anyway if you're unsure. MachinistPost evaluates condition on receipt. If it's not worth grinding, we'll tell you rather than grind a bad result.

WHAT YOU SHOULD ACTUALLY SEND

The vast majority of bits that get thrown away are fine resharpening candidates. A dull bit with a full-length body, clean flutes, and no physical damage is exactly what resharpening is for. If it's dull but structurally intact — send it.

Reserve retirement for: too short, worn flute margins, bent/cracked body, catastrophic tip damage where remaining length won't support a grind.

When in doubt, sort your discard pile and send the ones that pass a visual check. The cost of a regrind is almost always less than a new bit — and the geometry you get back is better than most new imported bits anyway.

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