01
Work hardening mid-cut
Feed and speed set wrong on a first pass, and the surface hardens under the tool. The next pass burns the insert and the finish turns rough. You pay for a re-cut, or you accept a part that fails roughness inspection.
CNC Machining · Stainless Steel
304 Stainless Steel CNC Machining
Milling and turning of 304 stainless steel parts to ±0.005 mm, with 16 simultaneous 5-axis centers in Dongguan. Quote and DFM feedback within 12 hours, from one prototype to 10,000+ parts.
304, 304L, 303, 316±0.005 mmRa 0.2–0.8 μmNo MOQISO 9001 / IATF 1694912-hour quote
15 yearsMachining stainless steel since 2011
127High-precision CNC machines
±0.005 mmAchievable tolerance on 304 parts
99.99%Qualification rate on shipped lots
Where 304 jobs go wrong
Problems That Show Up After the Parts Ship
Most stainless failures are process failures, not material failures. These are the ones buyers send back to us.
02
Threads that gall
Stainless galls against stainless. Parts that thread fine in the shop lock up at assembly when the mating part is also 304. Thread milling with the right pitch diameter and a controlled root radius avoids it.
03
Bore taper from heat
Without through-spindle coolant, heat builds at the cutting edge and the bore comes out tapered. A 20 mm deep bore can drift 0.03 mm from top to bottom. That shows up only when the mating pin will not seat.
04
Drawings that skip the passivation callout
Machined 304 carries free iron on the surface. Without a passivation step, rust spots appear on the shelf or in the field. The fix is cheap at the machine, expensive after the customer opens the box.
How we run it
Machining 304 Stainless Steel Without Guesswork
Tooling, coolant and speeds chosen for the alloy, not copied from an aluminum job.
Cutting strategy
Feeds, Speeds and Coolant Set for Austenitic Stainless
304 is austenitic. It does not harden before the cut, it hardens during it. Once the tool rubs instead of shears, the surface layer goes from around 200 HV to well past 300 HV and the next insert has to cut through that skin.
We run sharp, positive-rake carbide at moderate surface speed with a feed heavy enough to stay under the hardened layer. High-pressure through-coolant carries heat away from the edge instead of into the part. On thin-wall or long-reach features we drop radial engagement and accept a slower cycle rather than fight chatter.
- 1RoughingHeavy feed, light radial step-over, so the tool always bites fresh material.
- 2FinishingFresh inserts, small depth of cut, Ra 0.8–1.6 μm as machined.
- 3CoolantThrough-spindle high pressure on deep pockets and bores.
Geometry and inspection
5-Axis Work on Parts With Features on Five Sides
A 304 housing with ports, a flange face and a bore usually needs four or five setups on a 3-axis machine. Every setup adds a datum shift and a chance for error. On our simultaneous 5-axis centers the part stays in one fixture and the features come off one datum.
That matters most for position tolerance. A pattern of holes called out to ±0.05 mm across two setups is a coin flip; from one setup it is routine. We inspect 100% of parts before shipment and can supply dimensional reports on request.
- 1One datumFewer setups, tighter position between features.
- 2EnvelopeUp to 4,000 mm on the large-travel machines.
- 3VerificationRaw material check, in-process monitoring, final inspection.
Grade selection
Which Stainless Grade Fits the Job
304 is the default for corrosion resistance and cost. It is not always the right answer.
| Grade | Best for | Watch out for |
|---|---|---|
| 304 / 304L | Food, water, general corrosion, welded frames | Galls on threads; needs sharp tooling |
| 303 | Screw-machine parts, high-volume turning | Lower corrosion resistance than 304 |
| 316 / 316L | Chloride, marine, medical, chemical service | Higher cost, more tool wear |
| 17-4PH | High-strength shafts and valves | Heat treat step adds lead time |
| 420 / 440C | Wear surfaces, knife edges, bearings | Hard to machine after hardening |
What we do
Services Around Stainless Parts
One shop for the machining, the finishing and the inspection paperwork.
01
5-Axis CNC Machining
Simultaneous 5-axis for complex housings, impellers and multi-face parts from one setup.
02
CNC Milling & Turning
3-axis and 4-axis milling plus mill-turn centers for round parts with cross features.
03
Rapid Prototyping
One-off and low-volume stainless parts for fit checks before tooling is committed.
04
Part Surface Finishing
Passivation, bead blasting, brushing and polishing to bring 304 to the finish the drawing calls out.
05
Laser Marking & Engraving
Serial numbers, logos and traceability marks, minimum character height 1.5 mm.
06
Sheet Metal Fabrication
Laser cutting, bending and welding for 304 enclosures, brackets and frames.
Capability
Machines and Ranges Available for Stainless
| Item | Range | Notes |
|---|---|---|
| 5-axis centers | 16 simultaneous | One-setup multi-face work |
| 4-axis mills | 12 machines | Round parts with cross holes |
| 3-axis machines | 27 machines | Prismatic parts, plates, brackets |
| Mill-turn centers | 16 machines | Turned parts with milled features |
| Max part size | 4,000 mm | Largest travel 4,000 × 400 × 150 mm |
| Tolerance | ±0.005 mm | ±0.0002 in on qualifying features |
| Surface finish | Ra 0.2–0.8 μm | Fine finish on request |
| Rotary table | Ø400 mm | Indexed and simultaneous work |
Why GreatLight
Reasons Buyers Keep Sending Stainless Work
15Y
Fifteen years on stainless
Running since 2011, with cutting data built up from thousands of austenitic jobs rather than a tool catalog.
12h
Quote and DFM in 12 hours
You get a price and a manufacturability note the same working day, before you commit to anything.
24h
Production starts in 24 hours
Once the drawing and PO are confirmed, material goes to the machine the next day.
3–5d
Parts ship in 3–5 days
Standard stainless jobs leave the shop within the week after release.
150
Technicians on the floor
Programmers, machinists and inspectors across three wholly-owned plants.
7,600 m²
Manufacturing space
Dongguan plus a Singapore plant for customers who need a second shipping point.
127CNC machines
99.99%Qualification rate
<2%Historical late-delivery rate
No MOQOne part to 10,000+
Industry fit
What Each Industry Needs From a 304 Part
Medical devices
Housings and instrument bodies washed and sterilized repeatedly.
- Ra 0.8–1.6 μm
- 100% inspection
- ISO 13485
Automotive & EV
Brackets, sensor bodies and fluid fittings in volume.
- IATF 16949
- 3–5 day ship
- ±0.005 mm
Industrial machinery
Manifolds, valve bodies and shafts up to 4,000 mm.
- Large travel
- Passivation
- Reports on request
FAQs
Questions Engineers Ask Before Ordering 304 Parts
Can you hold ±0.005 mm on 304 stainless steel?
Yes, on features where the geometry allows it. 304 moves with heat and cutting load, so the tolerance depends on wall thickness, part length and how many setups the feature needs.
Send the drawing and we will tell you which callouts we can hold as drawn and which ones need a process change. We answer that in the same 12-hour quote window.
Should I use 303 instead of 304 to save cost?
303 machines faster and leaves a better finish, so turned parts get cheaper. It adds sulfur for machinability, and that lowers corrosion resistance.
Use 303 for internal screws, spacers and fittings that stay dry. Stay with 304 or 316 anywhere the part sees water, chlorides or cleaning chemicals.
Do you passivate machined 304?
We can include passivation as a finishing step. Machining leaves free iron and embedded tool material on the surface, and that is where rust spots start.
If the drawing calls for it, we run it. If it does not and the part is going outdoors or into a washdown environment, we will flag it during DFM review.
What is the smallest quantity you will run?
There is no minimum order quantity. We machine single prototypes and we run batches above 10,000 parts.
For one part, the setup cost dominates the price. If you expect volume later, say so up front and we will quote both paths in one response.
How do you stop threads from galling?
We control pitch diameter and root radius instead of cutting to nominal, and we keep the thread mill sharp. Thread milling beats tapping on 304 for this reason.
For mating stainless parts, specify a slightly different grade on one side, such as 303 against 304, or add a dry-film lubricant.
What surface finishes can you produce on 304?
As machined is Ra 1.6–3.2 μm. A controlled finishing pass reaches Ra 0.8–1.6 μm, and fine work goes to Ra 0.2–0.8 μm.
Beyond machining we offer bead blasting, tumbling, brushing and polishing, plus laser marking for traceability.
Can you machine 304 parts longer than a meter?
Yes. Our largest travel is 4,000 × 400 × 150 mm, with additional envelopes at 750 × 1,150 × 550 mm and 600 × 600 × 600 mm.
Long stainless parts deflect under cutting force. We plan support and light finishing passes rather than pushing a single heavy cut.
How do you handle confidentiality on new designs?
Uploads stay secure and confidential, and we sign an NDA on request before you send files.
We machine parts for customers in medical, automotive and defense supply chains, so drawing control is part of the routine here.
Send Your 304 Stainless Part for Quote
Upload the STEP file and drawing. You get a price and a manufacturability note within 12 hours, no minimum order quantity.
12-hour quote100% inspectionNo MOQNDA on request
