Stainless steel precision turning
Pins, shafts, bushings, fasteners — small-diameter, long and precise stainless parts are what a sliding headstock lathe exists for. Stainless is not a difficult material; it is a material that becomes difficult when it is cut wrongly. The difference lies in never letting the edge rub, not even for a moment.
The real problem: work hardening
Austenitic stainless grades (303, 304, 316) strain-harden at the surface roughly twice as fast as ferritic or martensitic grades. If the tool dwells on a freshly cut surface, that surface hardens within a fraction of a second, and the next pass meets a layer harder than the cutting edge itself.
Hence the old rule for stainless: twice the feed, half the speed. Stainless wants a lower cutting speed but a firm, steady feed. Backing the feed off does not save the cut — it forces the tool to rub and hardens the surface.
Which grade for which job
| Grade | What sets it apart | Where it is used |
|---|---|---|
| 303 | Sulphur added; chips break cleanly and it machines roughly twice as fast as 304 | Pins, shafts, bushings, fasteners, high-volume turned parts |
| 304 / 304L | Standard austenitic with no additive; balanced corrosion resistance | Bodies, brackets, food equipment, general industry |
| 316 / 316L | 2–3% molybdenum for superior seawater and chemical resistance; in return about 10–20% harder to machine than 304 | Marine hardware, chemical valves, surgical instruments, medical parts |
A practical warning: the corrosion resistance of 303 is slightly below 304 and it is not recommended for food, medical or marine use. Conversely, if your application does not genuinely need the corrosion resistance of 316, specify 304 — the material is cheaper and it machines faster, and both show up in the price.
Starting cutting speeds
The ranges below are a starting point for carbide tooling; they shift with the tool, the coating, the coolant and the rigidity of the setup.
| Grade | Turning (m/min) | Milling (m/min) |
|---|---|---|
| 303 | 75 – 120 | 45 – 90 |
| 304 / 304L | 45 – 90 | 30 – 75 |
| 316 / 316L | 35 – 75 | 25 – 60 |
How we do it
Small-diameter, long stainless parts run on our Star sliding headstock lathes. The advantage here is that the tool cuts immediately beside the point where the bar leaves the guide bushing: because the support sits close to the cut, deflection on a long slender part is reduced, which improves both dimensional consistency and surface finish. Prismatic and multi-face stainless parts go to our DMG Mori five-axis machining centres.
Inspection is in-house: a COORD3 ARES CMM with a Renishaw PH20 probe. On repeat batch work, measurement is built into the process rather than left to the end.
- A sharp edgeIn stainless a dull tool does not merely slow things down; it hardens the surface and ruins the next pass as well. Tool changes are planned.
- Uninterrupted cuttingDwelling, spinning idle and hanging in the air are where work hardening starts. The pass strategy is built around that.
- Chip evacuationLong stringy chips scratch the surface in stainless; chip breaking and evacuation matter as much as the cutting parameters.
- TraceabilityMaterial certificate, inspection record and declaration of conformity travel with the part.
What a quote needs
- A drawing or 3D model — STEP preferred, with a 2D drawing for tolerances.
- The stainless grade — 303, 304/304L, 316/316L or another; if you are unsure, tell us where the part will work and we will choose together.
- Quantity and lead time — Swiss-type turning rewards volume, so quantity directly sets the price.
- Surface treatment and documentation — passivation, electropolishing, inspection report, material certificate.
- stainless steel turning
- Swiss-type turning
- 303 stainless
- 304 stainless
- 316 stainless
- pins shafts bushings
- Ankara Ostim
Frequently asked questions
Should I specify 304 or 316?
If the application involves no seawater, salt or chemical exposure, 304 is enough. What 316 adds is the corrosion resistance of 2–3% molybdenum; specifying it on a part that does not need it raises both material cost and machining time, because 316 is markedly harder to cut than 304.
Why is 303 cheaper to machine?
Sulphur is added to 303 to make chips break cleanly. Because the chip breaks, cutting speed can rise and tool life extends; it machines roughly twice as fast as 304. In return its corrosion resistance is slightly below 304 and it is not recommended for food, medical or marine applications.
What is work hardening in stainless and how is it avoided?
When the tool begins rubbing instead of shearing, austenitic stainless hardens rapidly at the surface and the next pass meets a harder layer. Three things prevent it: a sharp edge, an adequate and steady feed, and never letting the tool dwell on the part. The fix is holding the feed, not raising the speed.
Can you make long, slender stainless parts?
That is exactly what a sliding headstock lathe is for. Because the part is cut right beside the guide bushing, deflection on long slender work is reduced; jobs that would need a tailstock and steady rest on a conventional lathe finish here in one operation.
Do you provide inspection reports?
Yes. Inspection is in-house on a COORD3 ARES CMM with a Renishaw PH20 probe. On request the inspection report, material certificate and declaration of conformity are sent with the part.
Send us your technical drawing and quantity; we will prepare your quote with a manufacturability review.
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