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.
Brand-neutral: no manufacturer pays for placement here. These ranges come from indexed catalogue data, not sponsorship.
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 · sfm) | Feed fn (mm/rev · ipr) | Notes |
|---|---|---|---|
| P Steel | 150–350 490–1150 sfm | 0.1–0.5 .004–.020 ipr | Lower for hard alloy steel and roughing, higher for finishing with a coated grade |
| M Stainless | 120–220 395–720 sfm | 0.15–0.4 .006–.016 ipr | Austenitic work-hardens; keep the tool moving, sharp positive geometry, flood |
| K Cast iron | 100–250 330–820 sfm | 0.2–0.5 .008–.020 ipr | Grey iron higher than ductile; usually dry |
| N Aluminium | 300–1200+ 985–3940+ sfm | 0.05–0.3 .002–.012 ipr | Sharp polished high-rake tools; very high speed is fine, keep chips clearing |
| S Titanium | 30–70 100–230 sfm | 0.1–0.25 .004–.010 ipr | Heat-limited; copious coolant, rigid setup, do not let it dwell |
| S Nickel superalloy | 15–50 50–165 sfm | 0.1–0.25 .004–.010 ipr | Inconel and similar; very heat-limited, rigidity is everything |
| H Hardened steel | 100–250 (CBN/ceramic) 330–820 sfm | 0.05–0.2 .002–.008 ipr | Hard turning with CBN or ceramic; carbide runs far slower here |
Starting ranges for coated carbide turning unless noted. SFM and ipr values are direct conversions of the metric ranges (1 m/min ≈ 3.28 sfm), rounded. 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 — or let the speeds & feeds calculator do it, metric or inch.
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.
For general carbide turning of ISO P steel, a common starting cutting speed (Vc) is roughly 150 to 350 m/min, lower for harder alloy steels and roughing, higher for finishing with a coated grade. Treat it as a starting range only and confirm the exact number against your specific insert and grade catalog, because the right speed depends on the grade, coating, operation and rigidity.
Titanium and nickel superalloys (ISO S) have very low thermal conductivity, so the heat generated in the cut stays concentrated at the cutting edge instead of flowing into the chip and workpiece. High speed would overheat and quickly destroy the edge, so starting speeds are low, often around 30 to 70 m/min for titanium and lower for nickel superalloys, with copious coolant and a rigid setup.
Cutting speed (Vc, in m/min or sfm) is the surface speed where the edge meets the work, and it mainly drives heat and tool life. Feed (fn, in mm/rev for turning) is how far the tool advances per revolution, and it drives chip load, cutting force and surface finish. You set the speed for the material and grade, then set the feed for the operation, roughing high, finishing low.
Spindle speed n in rpm equals 1000 times the cutting speed Vc in m/min, divided by pi times the diameter D in mm: n = (1000 x Vc) / (3.1416 x D). For example, Vc 200 m/min on a 50 mm diameter gives about 1273 rpm. In inch units, n = (12 x sfm) / (pi x D in inches).
Free, no strings: 8-brand grade cross-reference (PDF) · ISO material-group cheat-sheet (PDF) · US ANSI/ISO reference pack ($9, printable) · Speeds & feeds wall chart ($5) · Shop-floor field guide ($12, 16 pages) · All four PDFs bundled ($19, saves $12)
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