Food and beverage
304 and 316 fluid-handling and contact components, where corrosion resistance and finish drive the specification.
17-4 PH & 15-5 PH Stainless Machining Services
STAINLESS STEEL
CNC 17-4 & 15-5 PH Machining for High-Strength Service
17-4 PH is the alloy buyers reach for when a part needs the strength of a heat-treated alloy steel and the corrosion resistance of a stainless, and it is the alloy that most often arrives with an incomplete drawing. A print that says "17-4 PH" without a condition is asking for a part that could be HRC 33 or HRC 44 depending on who reads it — a 30 percent difference in strength and an entirely different machining plan.
Steelcrest Precision machines 17-4 PH and 15-5 PH across turning, multi-axis milling, grinding and wire EDM, and our multi-tasking platforms already run 17-4 H1075 and 17-4 PH as standard work. We turn to ±0.0005" and grind to ±0.0002", and we plan the ageing shrinkage into the process rather than discovering it at inspection.
Grades and Conditions We Run
Two alloys, four commonly specified conditions. The H-number is the ageing temperature in degrees Fahrenheit — the lower the number, the higher the strength and the lower the toughness.
| Condition | Hardness | Tensile (min) | What it's for |
|---|---|---|---|
| Condition A | ≤ HRC 38, typically 30–35 | - | Solution annealed. This is a MACHINING condition, not a service condition — it is untempered martensite with low fracture toughness and poor stress-corrosion resistance. Parts should be aged before they go into service. |
| H900 | ≈ HRC 44 | 190 ksi | Peak strength. Least tough, most notch-sensitive, poorest stress-corrosion resistance. Specified where strength governs and the environment is benign. |
| H1025 | ≈ HRC 38 | 155 ksi | The balanced choice, and the most common condition we see on commercial drawings. |
| H1075 | ≈ HRC 36 | 145 ksi | A common intermediate condition. Already standard work on our multi-tasking platforms. |
| H1150 | ≈ HRC 33 | 135 ksi | Overaged. Best toughness and best stress-corrosion resistance — the right call for subsea, marine and anything with a cracking risk. |
Tolerances and Surface Finishes We Hold On Stainless
Stainless is one of the materials where our published machine capability applies without a material penalty. It is stiff, dimensionally stable and thermally well behaved — the limits below are the machines' limits, not the material's.
| Process | Tolerance | Surface finish |
|---|---|---|
| CNC turning, standard | ±0.0005" | Up to 8 Ra turned |
| Precision turning | ±0.0002" | Up to 8 Ra, additional polishing available |
| CNC milling, 3- and 4-axis |
±0.001" (excluding true-position callouts) |
32 Ra side / 63 Ra face |
| 5-axis milling |
±0.001" linear · ±0.002–0.003" rotational · ±0.003" tilted-hole positioning | 32 Ra |
| INTEGREX / Hyper Quadrex mill-turn | ±0.0005" | 32 Ra |
| OD, surface and Blanchard grinding | ±0.0005" to ±0.0002" | Up to 8 Ra |
| Wire EDM | ±0.0005" to ±0.0002" | 16–32 Ra, fine finish to 8 Ra |
NOTE: Hardened 410, 420 and 440C reach HRC 58–60. Above roughly HRC 50 the finish operation is grinding or EDM, not cutting — so the tolerance you should quote from is the ground tolerance, not the machined one.
How We Machine Stainless Steel
Turning is the natural route for most stainless work. We run 28 CNC lathes with capacity to Ø26" × 160", with the precision sweet spot between Ø0.5" and Ø6". Four Swiss lathes handle bar-fed production up to Ø1.5" with 12-foot bar capacity — the right platform for 303 fittings and small turned details at volume. Three live-tool lathes and three Y-axis lathes add cross-drilling, milling and off-centre features without a second setup.
Prismatic and multi-face parts run on 36 vertical machining centers with capacity to 30" × 45", eight horizontal centers at 64" × 50" × 32" for production volume, and five five-axis verticals including Haas UMC-750 platforms. Where a part would otherwise need three setups, INTEGREX and Hyper Quadrex multi-tasking platforms cut it complete in one at ±0.0005".
Hardened martensitic grades finish in the grinding and EDM department: OD grinding to Ø16" × 60", surface grinding to 32" × 20" × 18", Blanchard to Ø15", honing to Ø8", five wire EDM machines and two RAM EDM machines for cavities and blind features.
What Makes 17-4 & 15-5 Different To Machine
Precipitation-hardening stainless is really two materials, before and after ageing, and the condition on the print decides everything about how the part gets made.
The condition decides the process
Annealed and H1150 material machines comfortably; H900 machines like a hardened part. When the print allows it, we machine in the softer condition and age afterward. When it calls for finished dimensions in H900, the process is planned around harder cutting, slower feeds, and finishing operations after heat treat. Same alloy, two different jobs, and the quote reflects which one the drawing is asking for.
Ageing moves the part
17-4 shrinks as it ages, predictably but not negligibly, and tight tolerances can disappear in the furnace. We machine oversize by the expected shrinkage, age, then bring critical features to final size by grinding or hard turning. The tightest diameters and datums on a PH part are always finished after ageing, never before.
15-5 is 17-4 with better manners
15-5 PH is the remelted, cleaner-chemistry cousin, with better toughness across the grain, which is why aerospace prints increasingly call for it. It machines nearly identically to 17-4, so the switch costs little at the spindle. If your part sees impact or through-thickness loading, 15-5 is worth a conversation before the drawing is final.
Finishing and Post-Processing
Some operations we perform in-house; others we manage through qualified partners and control
through our own quality system. We tell you which is which up front.
In-house at Steelcrest
- Ageing of 17-4 and 15-5 to the H900 through H1150 conditions, with shrinkage planned into the machining sequence
- Saw cutting and bar preparation
- Carbinite tungsten-carbide application by Electro Spark Deposition for wear surfaces
- Laser etching for part marking, lot codes and traceability
- Deburring, CMM and FARO Arm inspection
Managed through qualified partners
- Passivation to ASTM A967 for commercial work or AMS 2700 for aerospace
- Electropolishing to ASTM B912, or ASTM F86 for surgical implant work
- Bead blast, #4 and #8 mechanical polish
- Shot peening where fatigue-critical prints call for it (only if ops confirms this is actually offered — it's common for PH aerospace parts, but drop it if it's not real)
NOTE: Sequence matters on PH parts. We age first, finish critical features second, and passivate last, so the surface chemistry and the final dimensions both survive to inspection. Put the condition and the passivation spec on the drawing and the sequence takes care of itself.
Industries we machine stainless for
Medical and pharmaceutical — instrument components, fluid-path parts and housings in 303, 304, 316, 410 and 440C, where surface finish, cleanability and documentation matter as much as dimension.
Aerospace and defense
304, 316, 410, 420 and 440C housings, brackets, valve components and hardened wear details under AS9100.
Automotive
303, 304 and 316 fittings, fixture components and turned details, prototype through production.
We also machine stainless for chemical processing, marine and general industrial customers who reach us directly rather than through a named industry program.
Industries We Machine Stainless For
Steelcrest Precision machines 17-4 PH and 15-5 PH in conditions from annealed through H900 and H1075 for aerospace and defense, medical, and automotive applications.
We also machine stainless for chemical processing, marine and general industrial customers who reach us directly rather than through a named industry program.
Talk To Us About Your Stainless Steel Parts.
Send the drawing and the quantity. We will come back with a real number, a real lead time, and — if there is a better material or condition for what the part has to do — we will tell you that too.
Frequently Asked Questions
What conditions of 17-4 PH do you machine?
We machine 17-4 PH and 15-5 PH in the annealed condition and in aged conditions including H900, H1075, and H1150. When the print allows, we machine in the softer condition and age afterward; when finished dimensions are called out in the aged condition, we plan the process around harder cutting and post-age finishing.
Do you machine 17-4 PH before or after ageing?
Whichever the part requires. The most economical route is machining annealed or overaged material and ageing afterward, with critical features finished by grinding or hard turning after heat treat. Ageing shrinks the part, so tight tolerances are always brought to final size after the furnace, never before.
What tolerances can you hold on 17-4 PH?
±0.0005" on turned features as standard, ±0.0002" on precision-turned and ground features, and ±0.001" on milled features. The tightest diameters and datums on an aged part are finished by grinding after heat treat.
What is the difference between 17-4 PH and 15-5 PH?
15-5 PH is a remelted, cleaner-chemistry version of 17-4 with better toughness across the grain, which is why aerospace prints increasingly specify it. The two machine nearly identically, so switching costs little at the spindle. If your part sees impact or through-thickness loading, 15-5 is worth considering before the drawing is final.
Why does the H-condition on my drawing matter for cost?
Because it decides the machining plan. Annealed and H1150 material cuts comfortably; H900 machines like a hardened part and needs slower cutting and post-age finishing. A print that says "17-4 PH" without a condition leaves the strength and the machining plan undefined, and we will ask at quote.
Do you provide material certifications with 17-4 parts?
Yes. Material certifications and a certificate of conformance ship with the parts, and we can hold mill certs on file against your part number for repeat orders.