Wexmar provides Nitronic 50 CNC machining for marine propeller shafts, pump shafts, valve stems and fasteners that need more strength and corrosion resistance than 316 can offer. Nitronic 50 (UNS S20910, XM-19) is a nitrogen-strengthened austenitic stainless with roughly twice the yield strength of 316 in the annealed condition and better resistance to pitting and crevice corrosion in seawater. It is also one of the toughest stainless grades to cut, and pricing and scheduling should reflect that.
Nitronic 50 machinability
Nitronic 50 has an approximate machinability rating of 22 against AISI 1212 steel at 100, lower than any other stainless grade we routinely run. High-strength (HS) bar, which is strain hardened at the mill, is harder still. Cutting speeds are low, heat concentrates at the tool tip, and the material work hardens fast if the cut is interrupted or the edge dulls. Machine rigidity and stable workholding matter more here than with nearly any other stainless.
Because Nitronic 50 remains nonmagnetic even after heavy machining, it is also specified for instrument and sensor hardware where magnetic permeability must stay low. That property is worth protecting during processing: parts are kept away from carbon steel chips and tooling contamination, and cleaning before passivation removes embedded iron. Bar is usually bought annealed to ASTM A276 or A479, or as HS bar to a stated minimum yield, and the purchase spec affects both cycle time and material cost.
Tolerances and surface finish
With the right setup, typical Nitronic 50 work holds plus or minus 0.001 in. on turned diameters and bores, with tighter tolerances on selected features by agreement. Turned surfaces typically finish at 32 Ra to 63 Ra. Long shafts are supported with tailstock or steady rest, and journals needing finer finish can be finished on our centerless grinder. These results are typical and depend on length to diameter ratio.
Cutting practice: what works on Nitronic 50
- Rigid setups. Any chatter work hardens the surface and ruins the next pass. Short tool overhang and heavy workholding are required.
- Constant engagement. Keep feed and depth of cut steady and below the hardened layer from the previous pass. Never let the tool rub.
- Tool grades. Tough, sharp carbide with PVD coatings suited to heat-resistant alloys, often borrowed from nickel-alloy practice.
- Coolant. High-pressure coolant aimed at the tool tip controls heat and breaks the tough, stringy chips.
- Drilling and tapping. Use short, rigid carbide drills and thread milling instead of tapping where possible, since broken taps in Nitronic 50 are hard to remove.
- Tool change intervals. Set by count, not by visible wear, to protect finish and size.
Heat treat and finishing
Nitronic 50 is not hardenable by heat treatment; strength comes from nitrogen alloying and, in HS bar, mill cold work. Solution annealing or stress relief, when specified, is arranged through qualified outside processors. Passivation to ASTM A967 is also completed through qualified outside processors. Material certs and heat-lot traceability accompany every order when requested.
Common Nitronic 50 parts
- Marine propeller shafts and rudder stocks
- Pump shafts and valve stems for seawater and chemical service
- Fasteners, studs and bolting in corrosive environments
- Cable fittings and rigging hardware
Shafts run on our larger Mazak lathes, including the Nexus 450-II, where the spindle has the torque to hold a steady feed at low surface speed, while fittings and flanged parts can go to horizontal machining centers. Visit CNC turning for lathe capacity details.
Cost index comparison
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Baseline |
| 316 stainless | ~36 | 2.5 | Lower strength |
| 17-4 PH (Cond A) | ~40 | 2.8 | Hardenable, less seawater resistant |
| Nitronic 50 | ~22 | 4.5 | High strength, seawater service |
| Monel 400 | ~20 | 5.0 | Nickel-copper alternative |
| Inconel 625 | ~15 | 7.0 | Higher cost nickel alloy |
These values are typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing.
Industries and applications
Nitronic 50 machining at Wexmar supports marine and boat builders, pump and valve OEMs, chemical processing equipment makers and government build-to-print programs, with DFARS-compliant specialty-metals sourcing available. For a nickel-based alternative, see Monel 400 and K500.
Getting a quote
Specify annealed or HS bar and any passivation requirement. You can upload a drawing for an instant estimate or call (315) 400-2654. A human estimator confirms every quote.