Built-up edge (BUE): what it looks like, why it happens, how to fix it
Work material stuck to the cutting edge or rake face; the surface finish turns rough and the part size drifts as the deposit grows and breaks away. Adhesion and seizure at the tool-chip interface under high contact pressure. It is not welding: there is no fusion. It forms at low cutting speed and low edge temperature on ductile, "gummy" materials such as low-carbon steel, stainless and aluminium.
| What you see | Mechanism | First fix | Most affected |
|---|---|---|---|
| Work material stuck to the cutting edge or rake face; the surface finish turns rough and the part size drifts as the deposit grows and breaks away. | Adhesion and seizure at the tool-chip interface under high contact pressure. | Raise Vc so the edge runs hotter, and use a sharp, positive PVD geometry. | ISO P (steel), ISO M (stainless steel), ISO N (non-ferrous) |
Why it happens
- Cutting speed too low: below a material-dependent range the interface is cool enough for the deposit to stay stable.
- Negative or blunt geometry raises contact pressure and gives the material somewhere to sit.
- Coating and lubricity: a coating with high affinity for the work material, or poor lubrication, promotes adhesion.
How to measure and judge it
There is no wear land to measure. The signs are a deposit visible under magnification, a torn surface finish, and size that jumps when the deposit breaks off. When it breaks off it can take carbide with it, which is why BUE is a common cause of edge chipping.
Fixes, in the order to try them
- Raise Vc. Slowing down makes BUE worse, which is the opposite of the usual instinct.
- Use a sharp, positive-rake geometry with a PVD coating suited to the material.
- Improve lubricity: coolant concentration and type matter here.
- On aluminium, inspect the corner first: a dulled corner plows instead of shearing and builds up material.
Do not confuse it with
A deposit sitting in a hollow on the rake face can hide crater wear underneath. Remove it and look. See crater wear.
Other wear modes
Flank wear · Crater wear · Notch wear · Plastic deformation · Thermal cracking · Edge chipping and fracture · All eight failure modes in one table · Mechanisms in depth
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Frequently asked questions
What causes built-up edge on a cutting tool?
Built-up edge is caused by adhesion and seizure of work material on the edge at low cutting speed and low edge temperature, mostly on ductile materials such as low-carbon steel, stainless steel and aluminium.
Should I slow down to stop built-up edge?
No. Slowing down usually makes it worse. Raise the cutting speed so the edge runs hotter, and use a sharper, more positive geometry and better lubrication.