Feed & Speed Calculator for Copper
Soft and gummy rather than genuinely hard to cut — copper's main challenge is built-up edge, not force or heat.
Copper starting ranges
| Tool | Cutting speed (SFM) | Chip load, 1/2" 2-flute (in) |
|---|---|---|
| Carbide, polished flute | 300–600 | 0.004–0.007 |
| HSS | 100–200 | 0.003–0.005 |
Run at the lower end of these ranges if you're seeing built-up edge or a smeared finish, and raise chip load before raising speed.
Why copper fights the tool differently than steel does
Copper is soft and extremely ductile, so instead of shearing cleanly it tends to smear and stick to the cutting edge — built-up edge (BUE) forms when copper welds onto the tool tip, changing the effective geometry and producing a rough, tearing finish rather than a clean cut. This is a different failure mode than tool wear from a hard material, and it doesn't respond to the same fixes.
Sharp, polished, positive-rake tools matter more than speed
A sharp edge with a polished flute face and positive rake cuts copper cleanly with less tendency to build up material on the edge — a dull or coated tool meant for steel tends to make BUE worse, not better, since any roughness on the tool face gives copper something to stick to.
When you see smearing, raise feed before speed
A chip load too light lets the edge rub instead of shear, which is exactly the condition that encourages built-up edge — if the finish looks torn or smeared, try increasing chip load first. Slowing down (lower SFM) can help with heat-related issues in other materials, but in copper it's more often the wrong fix for a BUE problem.