Wexmar provides CNC machining of 316 stainless steel and its low-carbon version, 316L, for pump, valve, fluid handling, medical hardware and marine components. The molybdenum addition that gives 316 its resistance to chlorides and pitting also makes it one of the more demanding austenitic grades to cut. Our Canastota, NY shop turns, mills and Swiss-machines 316 every week, from single prototypes to repeat production lots, with material certs and heat-lot traceability available on request.
316 stainless machinability
316 carries an approximate machinability rating of 36 against AISI 1212 steel at 100. That puts it below 304 (approximately 45) and well below free-machining 303 (approximately 78). In practical terms, cutting speeds run roughly a third of what free-machining steel allows, and tool life is shorter at any given speed. 316L behaves almost identically at the spindle; the lower carbon matters for welded assemblies, not for machining time. Where a design allows it, some customers specify 303 for non-wetted parts and reserve 316 for surfaces that see seawater, cleaning chemicals or process fluids.
Typical tolerances and surface finish
On our lathes and horizontal machining centers, typical 316 work holds plus or minus 0.001 in. on diameters and bores, with plus or minus 0.0005 in. achievable on selected features when the drawing calls for it. Turned surfaces commonly finish at 32 Ra to 63 Ra, and milled faces at 63 Ra. Sealing faces and bearing journals can reach finer finishes with a light finishing pass or centerless and surface grinding in-house. These are typical results, not guarantees, and depend on wall thickness and part length.
Work hardening, tooling and chip control
316 work hardens quickly. A tool that rubs instead of cutting leaves a glazed, hardened skin that the next pass struggles to penetrate. The shop rules we follow are simple:
- Keep the feed up and never dwell. Light, tentative cuts do more harm than a confident depth of cut.
- Use sharp, positive-rake carbide inserts with honed edges and coatings suited to austenitic stainless.
- Run high-pressure flood coolant to control heat at the edge and to break the long, stringy chips 316 produces.
- Choose chipbreaker geometry for the actual depth of cut, and program peck or chip-break cycles on drilled holes.
- Replace tools on a schedule rather than running them to failure, since a worn edge quickly work hardens the surface.
Burrs on 316 are tough and ductile, so we plan deburring into the process rather than leaving it to hand work. Thin walls can move after roughing, and we leave finish stock on critical bores for that reason. Galling is another concern: 316 threads and sliding fits can seize against other stainless parts, so we recommend thread relief, anti-seize or a dissimilar mating material where the design permits.
Finishing and heat treat options
316 cannot be hardened by heat treatment. Stress relief or solution annealing, when specified, is arranged through qualified outside processors. The most common finish is passivation to ASTM A967 or AMS 2700, also handled through qualified outside processors, which removes free iron and restores the passive layer after machining. Electropolishing and laser marking can be coordinated the same way.
Common 316 parts and the right process
- Pump shafts, impeller hubs and sleeves on our CNC lathes with live tooling
- Valve bodies, manifolds and flanges on horizontal machining centers with pallet changers
- Small pins, fittings and instrument hardware on Maier Swiss machines to 32 mm diameter
- Marine hardware, sanitary fittings and sensor housings
Cost index: 316 compared with other materials
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Baseline |
| 303 stainless | ~78 | 1.8 | Free-machining, lower corrosion resistance |
| 304 stainless | ~45 | 2.2 | General-purpose austenitic |
| 316 / 316L stainless | ~36 | 2.5 | Chloride and pitting resistance |
| 17-4 PH stainless | ~40 | 2.8 | Hardenable, higher strength |
| Nitronic 50 | ~22 | 4.5 | Higher strength and corrosion resistance |
These values are typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing.
Applications and industries
316 stainless machining services at Wexmar support industrial OEMs building pumps and fluid power equipment, instrumentation makers, medical hardware suppliers and marine and chemical processing customers. Government build-to-print work is supported with DFARS-compliant specialty-metals sourcing. For comparison with a harder, heat-treatable option, see our 17-4 PH stainless page.
Getting a quote
Send your 316 or 316L drawing and quantity, and note any passivation or cert requirements. You can upload a drawing for an instant estimate or call (315) 400-2654. A human estimator confirms every quote before it goes out.