Most cutting problems announce themselves before the tool fails — in the chip, the sound or the surface. This page is the short version of what we tell customers who send us a photograph of a failed tool and ask what went wrong.
Chip color — reading the heat
| Chip appearance | What it means | What to change |
|---|---|---|
| Silver / straw colored | Cutting temperature is in range | Nothing — this is where you want to be |
| Blue or dark blue | Running too hot; heat is going into the tool as well as the chip | Reduce cutting speed, or improve coolant delivery / increase pressure |
| Black, or chips welded together | Well past the coating working temperature | Cut speed substantially; check whether the coating suits the material |
| Thin, stringy, no color | Chip load too light; the edge is rubbing rather than cutting | Increase feed per tooth; a rubbing edge wears faster than a cutting one |
Symptoms and causes
Chatter or a ringing sound
Usually a rigidity problem before a tool problem. Check the holder and the overhang first. If the setup is as rigid as it can be, a variable helix geometry is the answer — it changes the frequency at which the tool and workpiece vibrate.
Built-up edge on aluminium
The chip is welding to the edge. Raise the cutting speed, increase the feed to get under the built-up edge, and use polished flutes or a DLC coating. A hard coating makes this worse, not better.
Corner chipping
The sharp corner is taking all the load. Add a corner radius — even R0.2 mm changes the failure mode. Also check the tool entry: ramping in rather than plunging straight down removes a shock load.
Notch wear at the depth-of-cut line
A classic superalloy and titanium problem. Vary the depth of cut between passes so the notch does not form in the same place, and use a geometry with a reinforced edge at that zone.
Poor surface finish
Check runout first — it is the most common cause and the cheapest to fix. Then look at chip evacuation: recutting a chip will ruin the finish regardless of the tool.
Short, unpredictable tool life
If life varies widely between identical tools, the problem is usually in the setup rather than the tool: holder runout, coolant delivery, or a workpiece material that is not consistent batch to batch.
When to ask us
Send a photograph of the failed tool, the material and the cutting data you were running. The wear pattern on a failed edge usually says what went wrong, and it is quicker to read than to reproduce.