Military CNC Processing Services: How to Select a Supplier

• 1
  Key takeaways
• 2
  What to verify before you award the contract
• 3
  Tolerances that survive a defense drawing
• 4
  Material selection and heat-lot traceability
• 5
  Matching part size to machine travel
• 6
  Certifications, inspection and confidentiality
• 7
  Lead time, order size and finishing
• 8
  Seven steps to qualify a military CNC supplier

Defense drawings rarely ask for one tight dimension. They ask for a stack: bore diameter, bore position, perpendicularity to a face, and a surface finish that has to hold across the whole part. On a machined housing, a Ø40 mm bore at ±0.005 mm is routine on a good machine. The hard part is holding that bore concentric to a datum face after a second setup.

That is where machine count and machine type matter. A 5-axis center that machines five faces in one setup removes the re-fixturing error that a 3-axis sequence adds. GreatLight runs 16 simultaneous 5-axis machining centers alongside 12 four-axis mills and 27 three-axis machines, so the routing can be matched to the feature instead of forcing every part through one platform.

Surface finish is often the second hidden requirement. Ra 0.8–1.6 μm is a normal functional finish for a sealing or sliding surface. Ra 0.2–0.8 μm is available where a seal or bearing needs it, but it costs cycle time and usually needs a separate finishing pass. Put the Ra value on the drawing only where the function needs it.

One caution. A supplier who quotes ±0.005 mm on every dimension is not being generous, they are being vague. Tolerance belongs on the features that mate. Everything else can run at general tolerance and save you money.

Military hardware tends to land in a narrow band of materials: 7075 and 6061 aluminum for housings and brackets, 17-4PH stainless for corrosion resistance with strength, 4340 and 4140 steel for load paths, and TC4 (Ti-6Al-4V) where weight and temperature both matter. Inconel shows up in hot sections. Magnesium AZ31B and AZ91D appear in weight-critical housings but need chip-control discipline because the fines are flammable.

The sourcing question is not whether a shop can cut the material. It is whether the shop can prove which heat lot went into your parts. Ask for the mill certificate with the heat number, then ask how that number follows the part through the shop. A workable answer names the traveler, the inspection record and the final report. A vague answer means the traceability chain has a gap.

Machinability varies enough to move cost. 7075 cuts cleanly but stresses relieve after heavy material removal, so a rough-then-finish sequence with a stress-relief pause protects flatness. 17-4PH in the H900 condition is hard on tooling and needs slower feeds. TC4 moves and work-hardens, so climb milling with light radial engagement is standard.

If your part is a prototype, do not over-specify the alloy. A 6061-T6 bracket proves the geometry. Switching to 7075 for the production run changes the tool path and the inspection plan, so plan that transition early rather than after the first article.

Machine travel decides whether a part is one setup or four. GreatLight covers 4,000 × 400 × 150 mm for long parts, 750 × 1,150 × 550 mm and 600 × 600 × 600 mm for mid-size work, and 500 × 500 × 450 mm plus 500 × 310 × 200 mm for compact parts. A Ø400 mm rotary table handles round and indexable work. The largest envelope reaches a 4,000 mm maximum processing size.

Read that list against your drawing before you send it out. A 900 mm rail with bores on both ends fits the mid-size platform and can be machined from two ends in one setup if the table indexes. A 2,500 mm beam does not fit a 600 mm machine, and a shop that quotes it without asking is quoting a plan it cannot run.

Small parts have the opposite risk. A 40 mm connector body on a 4,000 mm machine wastes setup and fixture time. On a compact 500 × 310 × 200 mm platform, a pallet of parts runs faster and holds position better because thermal drift over the cycle is smaller.

The practical rule: send the bounding box, the tightest feature and the annual quantity in the same message. Those three numbers determine the machine, and the machine determines the price. Everything else is commentary.

Certification claims need scope. ISO 9001:2015 covers the general quality system. IATF 16949:2016 adds automotive-style process control and traceability discipline. ISO 13485:2016 governs medical devices. ISO 27001:2022 covers information security, which is the one that matters when your drawings leave your building. GreatLight holds all four, and the ISO 27001:2022 scope is the reason uploads can be handled under a controlled process rather than an email inbox.

Inspection is where a military program usually fails first. At GreatLight, inspection runs through raw material check, in-process monitoring and final inspection, with 100% inspection before shipment and reports available on request. Ask for a sample report with the quote. If the report lists only a pass stamp and no measured values, you cannot disposition a deviation later.

Documentation should be agreed before the first chip. Decide whether you need a first article inspection report, a certificate of conformance, material certs and a dimensional report on every lot, or only on the first. Each one adds handling time, and adding them after production starts is what causes late shipments.

Confidentiality runs in parallel. An NDA can be put in place before drawings are released, and controlled upload handling keeps geometry out of open channels. For defense work, the geometry is the asset. Treat the transfer path as part of the specification.

Lead time is a chain, not a number. GreatLight quotes with a free DFM analysis within 12 hours, can start production within 24 hours after approval, and ships parts in 3–5 days. Historical late-delivery probability is below 2%. Those figures assume the drawing is released, the material is standard stock and the finishing is in-house. Non-standard alloy plus outside plating plus a new inspection format is a different chain.

Order size is the other lever. There is no minimum order quantity, so a program can start with one prototype and scale to 10,000+ parts without changing suppliers. That continuity matters for defense work because the fixture, the tool path and the inspection plan carry forward. A new shop means re-proving all three.

Finishing changes fit. Anodizing adds a few micrometres per surface and can shift a bore or a thread if the callout does not account for it. Electroless nickel and hardcoat are thicker than clear anodize. If a part has a press fit after coating, say so on the drawing.

Laser marking is a common late request. Minimum character height is 1.5 mm, so a serial number or part number must fit the marked area at that size. Check the marking layout before release, not after the parts are finished.