AISI 316 Stainless Steel Rollers: Casting or CNC Machining?

A plain cylindrical roller with a bore is usually cheapest turned from 316 bar; a roller with flanges, spokes, pockets or a shaped hub is usually cheaper as an investment casting with only the bore and running surface machined. The deciding factor is how much metal would be cut away.

If turning from bar would remove roughly 60% or more of the material, a near-net-shape casting saves stainless steel and machining time. At several thousand pieces a year, the one-off cost of the aluminium wax-injection mould is spread over a large volume, so it adds little per piece. Many rollers end up as a hybrid: cast blank, then CNC-finished bore, faces and running diameter.

Yes, 316 (cast equivalent CF8M) is the usual choice, because its 2–3% molybdenum gives better resistance to chlorides than 304. It is not immune: tight crevices, trapped salt water and poor surface condition can still cause pitting or crevice corrosion.

Specify passivation after machining, keep the surface free of embedded iron (no carbon-steel tools or blasting media on finished parts), and design out narrow gaps where water can stand. Where the roller is in continuous seawater contact, ask us to review duplex 2205 as an alternative.

As-cast features follow CT4–CT6 (ISO 8062), about ±0.1 mm on small sizes; machined features such as the bore and running diameter can be held to about ±0.01 mm. As-cast surfaces are typically Ra 1.6–3.2 µm.

Mark on the drawing which diameters run on a shaft or bearing and which are cosmetic. Only the functional ones need machining; leaving the rest as-cast keeps the unit price down. If the roller must look polished, state the target finish (for example satin or mirror) because polishing is a separate cost.

Unit price, tooling cost if a mould is needed, MOQ, sample lead time and mass-production lead time, on the trade term you ask for (for example FOB or EXW). These are the five items we confirm before quoting a roller.

Our MOQ is 50 kg per order rather than a piece count, so a light roller can be ordered in a few hundred pieces, while the price is based on your annual volume. If the part can be made by more than one route, we explain the alternatives and their effect on price.

Typically 5–7 business days for the wax mould, 7–10 business days for samples after drawing approval, and 3–5 weeks for a standard production order. Shipping time comes on top.

For an annual part, the first order includes tooling and sample approval; repeat orders reuse the approved mould and start directly in production. Telling us the expected call-off dates for the year helps us plan melts and keep repeat lead times short.

A 2D drawing with tolerances plus a 3D file (STEP) is best; a photo alone is not enough to price a roller accurately. In the inquiry above, the drawing and 3D model were what allowed the process review to start.

Include: overall and detailed dimensions, tolerances, critical machining features (bore, keyway, running surface), surface finish or roughness, the grade (316/316L/CF8M), annual quantity and order frequency, and the trade term. If you only have a physical sample, we can evaluate from the sample, but say whether the part must copy it exactly.

An EN 10204 3.1 material certificate per heat is standard; CMM or dimensional reports are available on request. Chemical composition is checked by OES spectrometer for every heat.

If you need salt-spray results or a specific inspection plan for the running diameter, include it in the RFQ so it is priced from the start.