When to Retire a Drill Bit vs. When to Resharpen It

Resharpening makes economic sense on most HSS drill bits — but not all of them. Sending a bit that can't be salvaged to a regrind service wastes your money and the grinder's time. Throwing away a bit that has multiple useful regrinds left in it wastes the steel you already paid for.

The decision isn't complicated once you know what to look for. Here are the criteria, in the order you should evaluate them.

Step 1 — Check for Heat Damage (Steel Integrity)

This is the most important check and it's quick. Look at the shank of the drill and the body above the flutes. If you see blue, purple, or black discoloration running up the shank or body — not just at the cutting point where all drills show some color, but up the shaft — the drill has been overheated past its tempering temperature.

HSS loses its hardness irreversibly when it reaches temperatures that cause visible oxidation of the steel. A bit with heat discoloration up the shaft has soft steel. It will feel like it drills fine for the first few holes, then dull very quickly — because it is dulling very quickly. A regrind won't restore the steel hardness. That bit is done.

Blue/black up the shank = retire, do not regrind.

Discoloration at the very tip of the cutting point is normal and doesn't necessarily indicate a retired bit — the tip always sees the most heat. It's the discoloration traveling up toward the shank that matters.

Step 2 — Check for Physical Damage

Inspect the cutting lips and the flute body under good light. Look for:

• Chipping or chunking on the cutting lips — small chips are repairable if they're near the edge, because the regrind removes a small amount of material anyway. Large chips or multiple chips mean more metal has to be removed to get back to solid steel, shortening the bit more than a normal regrind would.
• Cracks in the body or flutes — a crack is a retire condition, full stop. There's no safe way to continue using a cracked bit, and grinding into a crack doesn't remove the failure mode.
• Bent or kinked flute — from a crash or overtorque event. Retire.
• Shank damage — gouges from chuck jaws, distortion from overtightening. Retire; the shank concentricity is gone.

Step 3 — Check Remaining Flute Length

Each regrind removes a small amount of steel from the point — typically 1/32" to 1/16" depending on how worn the bit was. A bit that has been reground many times is shorter than it started, and the point is now in thicker web territory, which means wider chisel edge and more thrust.

The functional limit is when the usable flute depth — the distance from the cutting point to where the flutes end — is no longer adequate to clear chips from the depth of hole you're drilling. As a rule of thumb: if the remaining flute depth is less than 1.5× the diameter, the bit should only be used for very shallow holes and is approaching the end of its useful life.

A bit that is clearly very short but still has usable flute depth can still be regrinded — it's just near the end of its cycle count. Worth a regrind for the remaining life it can provide.

The Verdict Matrix

What "Too Short" Actually Looks Like

For a standard jobber drill, the original flute length runs roughly 9 to 12 times the diameter. A 1/4" jobber starts at about 2.5" to 3" of flute. At the end of its regrind life, it might be at 2" of flute — still adequate for holes up to 3/4" deep (3× diameter), but not useful for deeper work.

Stubs like this often get kept around for through-holes in thin stock or very shallow spotting operations. That's legitimate — they're not general-purpose anymore but they have specific uses. It's worth knowing what you have.

The Regrind Economics at Each Stage

A quality 3/8" HSS drill costs roughly $5 to $8 new. A regrind costs less. Even at the third or fourth regrind cycle — when the bit is shorter and the chisel edge has grown from moving into thicker web — a regrind still makes sense if the steel is good, because you're buying another batch of holes at below-replacement cost.

The math tips toward retirement only when the bit is so short that its usability is limited, or when the cost of evaluating and shipping a marginal bit approaches the cost of just buying a new one. For most shop sizes, the threshold for replacement over regrind is pretty clear: broken, heat-damaged, or flute-depleted bits go in the scrap metal bin, everything else goes in the regrind pile.