| China Precision ManufacturingCustom Stainless Steel CNC Machining Services
Send us your drawing and you get a free DFM report before a single chip is cut. We machine 304, 316, and 17-4PH stainless steel, from one-off prototypes to 10,000-piece runs. Every shipment carries a CMM report and a material certificate, and the quote you approve is the price you pay.
Free DFM flags work-hardening, thin-wall, and tolerance risks before we cut
303/304/316/17-4PH held to ±0.005mm, CMM-verified
Mill material cert + CMM report with every stainless steel batch
CNC Machining Stainless Steel Capabilities
We run imported Fanuc CNC machining centers and CNC lathes for stainless work across milling, turning, and Swiss-type production. Standard tolerance is ±0.01mm, tightened to ±0.005mm on critical features where the drawing calls for it, with as-machined surfaces down to Ra 0.8. When a feature cannot be reached by an end mill, we finish it on our Sodick mirror EDM or wire EDM, so internal corners and deep slots stay true to print.
What we machine in stainless steel:
3-, 4-, and 5-axis milling
Faces, drilled holes, tapped threads, 3D contours
CNC turning
Shafts, bushings, discs, and other rotational parts
Swiss machining
Long, slender, small-diameter precision parts
Mill-turn
Most features in one setup, fewer re-clamps, tighter accuracy
Part envelopes run from small fittings to mid-size housings, in grades from free-cutting 303 to work-hardening 316 and precipitation-hardened 17-4PH. Every job ships as CNC machined stainless steel parts with CMM-verified dimensions tied to your drawing.
Which grade you pick drives tool wear and cost more than any other decision, so here is how the common stainless alloys compare on the floor.
Stainless Steel Grades We Machine
Grade choice sets tool life, finish, and price before the first cut. The table below reflects parts we run in volume, not spec-sheet theory.
| Grade | Machinability | Corrosion resistance | Typical parts |
|---|---|---|---|
| 303 | Excellent (~75%) | Good | Fittings, shafts, fasteners |
| 304 / 304L | Good | Good | Enclosures, brackets, food gear |
| 316 / 316L | Tough, gummy | Superior (chloride) | Medical, marine, pump bodies |
| 416 | Good | Fair | Gears, valve parts, drive shafts |
| 420 | Fair, hardenable | Good | Blades, molds, wear parts |
| 17-4PH | Good | Excellent + strength | Aerospace, medical, high-load shafts |
303 breaks chips cleanly and suits high-volume turned parts where welding is not needed.
316/316L adds molybdenum for chloride and pitting resistance — the reason it dominates medical and marine work.
17-4PH machines predictably and reaches high strength after heat treatment, the choice for aerospace and load-bearing shafts.
416 and 420 are martensitic and can be hardened, common for gears, valve seats, and wear parts.
If your print has not locked a grade, send the application and load case. We will recommend the alloy that hits your corrosion and strength targets at the lowest machining cost.
The 300-series grades share one trait that defeats new shops, so it is worth showing exactly how we handle it.
Why Stainless Steel Is Hard to Machine — and How We Solve It
Stainless fights back in three ways. Each one wrecks tools and parts when ignored, so each gets a specific countermeasure on our floor.
Work-hardening
Austenitic grades like 304 and 316 harden the instant a tool rubs instead of cuts, and the next pass meets a layer harder than the cutter.
Solution
We keep the tool cutting continuously and set depth of cut and feed deeper than the hardened layer, so the edge always engages soft base metal.
Poor heat conduction
Stainless carries heat at roughly one-third the rate of carbon steel, so almost all of it loads onto the tool tip and the part.
Solution
We run high-pressure flood coolant to flush chips and pull heat from the cutting zone, and match cutting speed to the grade to hold thermal growth in check.
Built-up edge
High-melting-point carbides weld material onto the cutting edge, dragging finish and accuracy.
Solution
We use TiAlN-coated solid carbide with adequate relief angle, on rigid setups that suppress vibration on thin walls and slender features.
The rules we hold to:
Sharp, coated carbide only — dull edges trigger work-hardening
Lower cutting speed, heavier positive feed to shear cleanly
Flood coolant on every drilling and finishing pass
Rigid work-holding to stop chatter on thin-wall parts
Most of these failures are predictable from the drawing before a single tool moves, which is exactly what our DFM step catches.
Free DFM Analysis Before We Cut
Stainless punishes design oversights harder than aluminum. A 0.8mm wall that machines clean in aluminum will chatter and deform in 316. That is why every stainless file passes a Design for Manufacturability (DFM) review at the quoting stage — while a fix still costs nothing more than a reply email.
Each DFM report on your stainless parts flags the risks that drive scrap and rework:
Thin walls below 1.0–1.5mm that vibrate and warp under cutting load
Deep cavities past a 4:1 depth-to-width ratio that force long tools and chatter
Sharp internal corners no end mill can reach, with the radius we recommend instead
Over-tight tolerances that add cost without adding function
Blind tapped holes without thread-relief depth for tap chip clearance
A clean drawing gets quoted as drawn. A risky one comes back with the specific feature marked and a workable change beside it. The point is simple: you learn what stainless will fight before the spindle starts, not when the carton is opened.
CTA
Send us your stainless steel drawing and we will return a free DFM report flagging work-hardening, thin-wall, and tolerance risks before a single chip is cut.
Upload your CAD → free DFM check + 24-hour replySurface Finishes for Stainless Steel Parts
Finish choice affects corrosion resistance, appearance, and coating adhesion. Most parts we ship to US and European buyers leave the machine as-machined — no extra step, lowest cost, shortest lead time. The four finishes we run most often are below, followed by options on request.
As-machined*
Raw cut surface, no post-process
Use
Functional and internal parts
Passivation*
Removes free iron, builds chromium-oxide film
Use
Medical, food, marine parts
Polishing*
Lowers Ra toward smooth or mirror
Use
Visible parts, fluid paths
Bead blasting*
Uniform matte, hides tool marks
Use
Cosmetic parts, pre-coat base
Available on request: PVD coating (titanium or zirconium, for hardness and color), electroplating, and electrochemical polishing.
*Most requested by our export customers. Passivation behaves differently on 303 than on 316, so we confirm the right finish for your grade at quote. A finish only holds value if the dimensions under it are verified — which is where inspection comes in.
Quality Control & Inspection
Every order ships with documentation, not just parts. Tolerances mean nothing without proof, so we measure and record before anything leaves the floor.
CMM report
Toleranced bores and faces verified to datums, where stainless thermal growth is easy to miss by hand
Material certificate
Alloy and melt traceable to source
Roughness tester
Ra checked on as-machined and passivated faces against print
Profile projector
Small profiles and threads verified
Pin & plug gauges
Go/no-go on bores that work-hardening can pull off size mid-run
Hardness tester
Confirms 17-4PH and 420 reached the specified condition after heat treatment
Traceability log
Batch tied to setup and operator
Tight tolerances are confirmed on the CMM, not estimated by eye, and the report is logged against your part number. That trail holds consistency across repeat orders, where batch-to-batch drift is what hurts your yield.
A logged inspection trail matters most in the sectors where one out-of-spec part stops a line or fails an audit.
Stainless Steel Parts We Machine Across Industries
Stainless earns its place wherever corrosion, hygiene, and load matter at once. We machine 304, 316, and 17-4PH parts for buyers supplying:
Medical
316L surgical bodies and housings, passivated to ASTM A967
Aerospace
17-4PH brackets and fittings stable under heat and vibration
Food & Beverage
316 valves and pump parts that resist wash-down pitting
Marine
316 hardware built for salt spray and standing-seawater exposure
Automotive
304 exhaust, fuel-system, and engine-mount components
Precision Instruments
Sensor housings and optical mounts to tight flatness
What that capability looks like on real parts is clearer from the jobs themselves than from any list.
Stainless Steel CNC Machining Case Studies
Specs prove capability; parts prove experience. The examples below are de-identified — client names and logos removed, technical detail intact. We sign an NDA before any file opens.
Challenge
Holding dimensional consistency across a 2,000-piece run
Solution
Mill-turn in one setup, with in-process CMM checks per batch
Result
Stable batch-to-batch dimensions, full traceable QC record
Challenge
Thin internal walls prone to chatter in gummy 316
Solution
Multi-point fixturing, continuous cutting, flood coolant
Result
Passivated finish, CMM-verified bores, no measurable deformation
Challenge
High hardness after heat treatment with tight flatness called out
Solution
Coated carbide tooling, rigid setup, staged roughing then finish
Result
Flatness held and logged, full material certificate supplied
Challenge
Cosmetic surfaces plus a strict corrosion specification
Solution
Sharp tooling, controlled feeds, passivation per print
Result
Bead-blasted finish, passivated, traceable QC across the batch
Every one shipped with the same proof package — inspection data, material certificate, and a record of how the part was made — at the price quoted.
CTA
From a single 316 prototype to a 10,000-piece 17-4PH production run, get your quote with CMM report and material cert included, no hidden fees.
Send your drawing for pricingWhy Source Stainless Steel CNC Machining from KTM in China
You are not buying spindle hours. You are buying a supplier that flags a thin wall or an unmachinable internal corner before the chip is cut, not after the shipment lands.
KTM runs 80 people out of Dongguan, and stainless is where an engineer-led shop pulls away from a quote desk. Setting feed and depth against a work-hardening layer, or calling whether a 17-4PH pocket needs EDM instead of a longer end mill, is judgment built on the tool — not pulled from a price table.
Our founder brings a mold-design background and two decades spent setting the hardest stainless jobs in person. The engineer who answers your 316 tolerance question has cut the grade, not just priced it.
| What you weigh | How we handle it |
|---|---|
| Mid-project price jumps | The figure you approve is the figure you pay — locked before the first cut, with no rework or engineering line added later |
| Small batches turned away | No floor on quantity; a single 316 first article scales to multi-thousand-piece 17-4 PH runs on the same setup |
| Outsourced steps and delays | Milling, turning, Swiss, EDM, and CMM all stay inside one team |
| Time-zone silence | Project engineers cover US and EU working hours from China, so a stainless DFM query rarely waits a full day |
| Design exposure | An NDA is in place before your STEP file is opened |
Three clients have stayed 15, 10, and 6 years — that retention is the proof, not a slogan. KTM holds ISO 9001, and our automotive and medical parts ship to those customers own part-level standards.
Before a stainless job reaches any of that, it helps to see the exact path a part takes through our floor — six steps, and no surprises between quote and delivery.
How We Work — From CAD to Stainless Parts
Six steps move every stainless order from your file to a documented part. Each one is fixed, and you confirm the cost before any tool touches metal.
Upload your CAD
Send STEP, IGES, or X_T, with a 2D control drawing marking toleranced features and datums. We sign an NDA first if you ask.
DFM review
An engineer checks wall thickness against stainless chatter limits, depth-to-width on pockets, and any internal corner an end mill cannot reach. Anything that drives scrap or work-hardening is flagged, with the fix marked, before you commit a cent.
Transparent quote
Grade, finish, tolerance, and quantity each sit on their own line. The price you approve holds through the job. If a part ships out of spec because of our machining, we recut it at our cost.
Machining
Milling, turning, Swiss, or EDM, with feeds and coated-carbide tooling set for how that specific grade work-hardens — 303 and 316 run very differently under the same cutter.
Inspection
A CMM dimensional report and mill material certificate ship with the parts, plus hardness data where 17-4PH or 420 calls for it.
Delivery
Lead time typically runs 5 to 20 working days, set by grade, geometry, and quantity, and confirmed in your quote.
With the path laid out, a few specific questions usually remain. Here are the ones engineers ask most before they send a file.
Stainless Steel CNC Machining FAQ
Yes. Stainless is fully machinable but sits in "hard mode" next to aluminum. It work-hardens when a tool rubs, holds heat in the cutting zone, and throws long, stringy chips. Rigid work-holding, sharp coated carbide, a steady chip load, and flood coolant make it routine. We run austenitic, martensitic, and PH grades daily.
316 is harder. Added molybdenum and higher nickel make it gummier and push its work-hardening rate roughly 15% above 304. Both need sharp tooling and flood coolant; 316 needs heavier feeds and closer tool-life monitoring.
303 is significantly easier. Added sulfur breaks chips cleanly and avoids the stringing that plagues 304. The trade-off is lower corrosion resistance and poor weldability, so 304 stays the choice for welded or marine parts.
303, 304/304L, 316/316L, 416, 420, and 17-4PH — matched to function. 316L for medical and marine, 17-4PH for aerospace strength, 303 and 416 for high-volume turned parts.
General features run to ±0.01mm; critical fits to ±0.005mm, confirmed on a CMM with the report shipped alongside the parts. We mark tight tolerances only on mating surfaces, since over-specifying every dimension adds cost and scrap with no functional gain.
Yes. Every order can ship with a mill material certificate, a CMM dimensional report, and surface-finish data, backed by a traceable record.
There is no minimum. We machine single prototypes and scale the same part to production once the design is proven. Many customers start with one stainless part and move to recurring runs after the first-article approval.
Price reflects grade, geometry, tolerance, finish, and quantity, and is fixed before cutting begins. There is no low quote followed by a mid-project surprise.
Stainless costs more per part than aluminum, and the gap comes from the metal, not a markup. Grade drives it first: free-cutting 303 machines fast, while 316 and 17-4PH work-harden, wear tooling quicker, and run at lower cutting speeds, so machine time climbs. Heat treatment on 17-4PH and finishes like passivation add their own lines. Setup is a one-time charge, so a single prototype carries it alone, while a 100-piece run spreads it thin across each part. Send the file and the quote itemizes each driver against your actual geometry.
Have a grade or tolerance not listed here? Send the file and we will answer against your actual geometry.
Request Your Stainless Steel CNC Machining Quote
Upload your CAD and we return a free DFM check plus a fixed quote. Where the drawing carries risk, we flag the work-hardening, thin-wall, or tolerance issue first, then quote the part that will actually machine.