Feed & Speed Calculator for Inconel
The hardest common material on this site to machine well — low speed, rigid everything, and tools you replace on a schedule, not when they look dull.
Read this before cutting anything. Inconel and other nickel superalloys generate extreme heat, work-harden aggressively, and destroy tools fast when the numbers are even slightly wrong. These are conservative starting points for general-purpose coated carbide, not production numbers — if you have access to your insert manufacturer's actual Inconel data (many publish alloy-specific charts), use that instead. This is expensive material to learn on by trial and error.
Inconel starting ranges (coated carbide)
| Tool | Cutting speed (SFM) | Chip load, 3/8" 4-flute (in) |
|---|---|---|
| Coated carbide, rigid setup | 30–80 | 0.002–0.004 |
| HSS/Cobalt | 10–20 | 0.001–0.002 |
Production shops with ceramic or CBN inserts and very rigid, high-power machines can run faster than this — these ranges assume general-purpose coated carbide on a typical VMC.
Why Inconel is in a different category from stainless
Nickel superalloys retain their strength at temperatures that would soften steel, which is exactly why they're used for turbine and high-temperature aerospace parts — and exactly why they don't get easier to cut as the tool heats up the way steel does. Heat that would help a steel cut instead keeps the workpiece just as tough right at the cutting edge, so speeds have to stay low to keep heat generation manageable at all.
Work hardening here is worse than in any stainless
The same rule as stainless applies with much less margin for error: any rubbing, dwelling, or light finishing pass hardens the surface, and Inconel's work-hardened layer is dramatically tougher than the base material already is. A tool that hesitates for even a moment can turn the next pass into a much harder cut than the first one was.
Tool life is a schedule, not a judgment call
Because a rapidly dulling edge accelerates heat and work hardening in a feedback loop, production shops replace inserts on a fixed cycle count or time interval rather than waiting for visible wear — by the time an edge looks dull in Inconel, it's already been generating excess heat and hardening the surface for a while. Budget for more tool changes than any other material on this site, and don't try to stretch a tool's life here the way you might in steel or aluminum.