A starting cutting speed gets you safely into the material. The right number comes from your specific insert's catalog, or from the chip and the wear in front of you. Here are brand-neutral starting ranges by ISO group for carbide turning, plus the math and the method to dial them in. Always confirm against your tool maker's data, or ask the advisor for the verified number for your exact insert.
Every speeds-and-feeds decision is these three. Know what each one buys and what it costs before you touch a number.
| Lever | Controls | Raise it for | Watch |
|---|---|---|---|
| Cutting speed (Vc) | Edge temperature and tool life | Productivity, and to get hot enough to beat built-up edge | Crater wear and plastic deformation when too high |
| Feed (fn) | Chip load, cutting force, surface finish | Productivity and reliable chip breaking | Rough finish and edge chipping when too high or too low |
| Depth of cut (ap) | Metal removed and which part of the edge is loaded | Fewer passes, faster roughing | Power limit, and notch wear at the depth-of-cut line |
Set the speed for the material and grade first. Set the feed and depth for the operation: roughing wants depth and feed, finishing wants a light depth, a controlled feed and the nose radius doing the work.
These are starting ranges from common practice for coated carbide turning, not gospel and not from any one catalog. The verified number for your exact insert, grade and operation lives in the maker's data. Start mid-range, then let the chip and the wear move you. For the grounded per-insert number, ask the advisor.
| Group | Starting Vc (m/min) | Feed fn (mm/rev) | Notes |
|---|---|---|---|
| P Steel | 150–350 | 0.1–0.5 | Lower for hard alloy steel and roughing, higher for finishing with a coated grade |
| M Stainless | 120–220 | 0.15–0.4 | Austenitic work-hardens; keep the tool moving, sharp positive geometry, flood |
| K Cast iron | 100–250 | 0.2–0.5 | Grey iron higher than ductile; usually dry |
| N Aluminium | 300–1200+ | 0.05–0.3 | Sharp polished high-rake tools; very high speed is fine, keep chips clearing |
| S Titanium | 30–70 | 0.1–0.25 | Heat-limited; copious coolant, rigid setup, do not let it dwell |
| S Nickel superalloy | 15–50 | 0.1–0.25 | Inconel and similar; very heat-limited, rigidity is everything |
| H Hardened steel | 100–250 (CBN/ceramic) | 0.05–0.2 | Hard turning with CBN or ceramic; carbide runs far slower here |
Starting ranges for coated carbide turning unless noted. Subgroup, grade, coating, operation, coolant and rigidity all shift the number. Confirm per insert.
The machine wants RPM, the catalog gives you a cutting speed. This is the one conversion every operator needs.
Example: Vc 200 m/min on a 50 mm diameter is (1000 × 200) / (3.1416 × 50), about 1273 rpm. In inch units, n = (12 × sfm) / (π × D in inches).
For a turned finish, theoretical roughness rises with the square of the feed and falls with the nose radius. In practice that means: to halve your roughness, you do not need to crawl, you can drop the feed a little or step up the nose radius. A bigger nose radius finishes better at the same feed, at the cost of higher radial force and chatter risk on slender parts.
Change one variable, re-cut, re-read. The chip and the wear are better data than any starting table.
Starting ranges are deliberately wide because the real answer depends on your exact grade and operation. That is the brand-neutral problem this tool solves: it grounds the recommendation in real catalog data and tells you when there is no verified match, instead of inventing one.
Free, no strings: 8-brand grade cross-reference (PDF) · ISO material-group cheat-sheet (PDF)