Wexmar performs CNC machining of 17-4 PH stainless steel (UNS S17400, Type 630) for shafts, valve trim, fasteners, actuator parts and defense hardware. 17-4 PH combines corrosion resistance close to 304 with strength that can be raised well above any 300-series grade through a single low-temperature aging treatment. That flexibility makes it a common choice for parts that need both stiffness and resistance to wet environments, and it is a regular material at our shop in Central New York.
17-4 PH machinability by condition
In Condition A (solution annealed), 17-4 PH has an approximate machinability rating of 40 against AISI 1212 steel at 100. The practical difference is that 17-4 PH is usually supplied or machined in a specific condition, and each condition behaves differently:
- Condition A: roughly 30 to 36 HRC, approximately 40 on the 1212 scale, the usual starting point when parts will be aged after machining.
- H1025 and H1150: overaged, somewhat softer and tougher, machine at similar or slightly better rates than Condition A.
- H900: around 40 to 44 HRC, slower speeds and more frequent tool changes, but no post-machining distortion from aging.
Tolerances and surface finish
Typical 17-4 PH work holds plus or minus 0.001 in. on turned and bored features, with plus or minus 0.0005 in. possible on selected diameters. Turned surfaces generally finish at 32 Ra, and milled surfaces at 32 Ra to 63 Ra. Because aging causes a small, predictable dimensional change (a slight contraction), precision 17-4 turned parts that will be aged after machining either leave finish stock for a final pass or are held to tolerances that absorb that change. These figures are typical and depend on geometry.
Shop gotchas: tooling, heat and sequence
17-4 PH does not work harden as severely as 316, but it is abrasive and generates heat at the tool tip. Much of the cost on a 17-4 job comes from choosing the wrong sequence, so we settle the condition and stock allowances with the customer before programming. What matters on the floor:
- Decide the machining sequence up front. Rough in Condition A, age through a qualified outside processor, then finish critical features, or machine complete in the aged condition.
- Use carbide grades built for stainless and hardened steel, with strong edge preparation for H900 material.
- Keep coolant concentration up and flow high; heat checking and built-up edge shorten tool life quickly.
- Chips are tougher than on 300-series stainless, so chipbreaker selection matters on long turning passes.
- Threads cut in H900 need sharp tooling and conservative infeeds to avoid torn flanks.
Heat treat and finishing
Precipitation hardening to H900, H1025, H1075 or H1150 is performed through qualified outside processors, with hardness test results and processor certs available. Passivation to ASTM A967 or AMS 2700 is also handled through qualified outside processors. Parts aged after machining typically need passivation afterward to remove heat tint.
Common 17-4 PH parts and process fit
- Pump and valve shafts, stems and seats on Mazak and Doosan lathes with Y-axis
- Actuator bodies, brackets and manifolds on horizontal machining centers
- Small pins, bushings and fastener blanks on Maier Swiss machines with bar feeders
- Aerospace and defense hardware built to print
Swiss turning suits 17-4 PH well because the guide bushing supports slender parts close to the tool, which limits deflection in a material that pushes back hard. Long pins with length to diameter ratios above 8 to 1 are usually better on Swiss than on a conventional lathe. Larger shafts and flanged parts stay on the lathes, where live tooling and Y-axis add flats, cross holes and keyways without a second setup. See our Swiss machining page for small-diameter work.
Cost index
| Material | Approx. machinability (1212 = 100) | Cost index vs 6061 | Notes |
|---|---|---|---|
| 6061-T6 aluminum | ~180 | 1.0 | Baseline |
| 304 stainless | ~45 | 2.2 | Not hardenable |
| 316 stainless | ~36 | 2.5 | Higher corrosion resistance |
| 17-4 PH (Cond A) | ~40 | 2.8 | Age hardenable after machining |
| 15-5 PH | ~40 | 3.0 | Better transverse toughness |
| 4140 prehard | ~50 | 1.6 | Strong, needs a coating for corrosion |
Values are typical and illustrative for a comparable part; actual quotes depend on geometry, quantity, tolerances and mill pricing.
Applications and industries
Our 17-4 PH stainless machining services support fluid power and pump OEMs, oil and gas valve builders, aerospace hardware suppliers and government build-to-print programs. DFARS 252.225-7009 compliant specialty-metals sourcing, AS9102-format FAI and CMM reports are available. Learn more about our government and defense machining, or compare with 15-5 PH stainless.
Getting a quote
Tell us the condition you want to buy and the condition the part must end in. You can upload a drawing for an instant estimate or call (315) 400-2654, and a human estimator confirms every quote.