Questions to Ask a CNC Supplier Before You Send a Print

Alloy and material questions

Alloy fluency is the fastest filter. These questions surface whether the shop actually runs your material family or is going to learn on your part.

• Do you run [specific alloy] weekly? — Weekly is the threshold. Monthly means unfamiliar; quarterly means the operator's forgotten the setup.
• Do you stock this alloy? — Stocked material is what enables emergency turnaround. If it has to come from a mill, add 2–4 weeks.
• What condition/temper do you machine it in? — For 17-4 PH: Condition A vs H900 vs H1150 are different machining problems. The shop should know which you need.
• Have you machined [specific application] before? — Ask for the closest reference job. Not case-study photos — just "yes, we've done that" or "no, first time."
• How do you handle exotic-alloy scrap/rework? — Reveals whether they respect the material cost. A shop that shrugs on Inconel rework isn't the shop for your job.

Tolerance and inspection questions

• What's your routine tolerance on this feature class? — Ask about your specific feature — not "tight tolerance" but a real number for the bore or the finish.
• How do you verify critical dimensions? — CMM should be the answer for critical features. If "we use calipers," you're not in the right shop.
• Do you produce first-article reports? — Yes, on every job, standard — that's the expected answer for oilfield/aerospace work.
• Can I see a redacted first-article report from similar work? — A shop that's done it can show it. A shop that hasn't will hedge.
• What's your surface-finish measurement equipment? — Profilometer for critical finishes. "Visual" or "comparator" isn't sufficient for seat grooves or sealing surfaces.

Documentation and quality questions

• Do you provide a Certificate of Conformance on every job? — Yes, standard. This is baseline for oilfield/aerospace work.
• Do you support customer ITPs (Inspection and Test Plans)? — For API-adjacent work: yes. If the shop resists, they're set up for general fabrication.
• Can you produce a PPAP-style package on demand? — Standard for aerospace/defense. Sometimes required for critical oilfield work.
• How do you handle material traceability? — Heat and lot documented on every part. Certified against the mill test report.
• What's your ITAR posture? — For defense work: shop should have document-control and NDA processes in place. If they don't know what ITAR means, wrong shop.

Timeline and capacity questions

• What's your typical lead time for [this alloy] in [this quantity]? — Should get a specific answer, not "depends." 2–3 weeks for standard oilfield work in stocked alloys is normal.
• What's your emergency response like? — For rig-down work with stocked material: realistic same-day to 3-day depending on part. If they claim same-day guaranteed on any job, that's marketing not reality.
• Who do I call for an emergency? — Should be a direct shop-floor number. A form or a ticket portal is a bad answer for oilfield work.
• What's your current capacity utilization? — Hard for shops to answer honestly. But if they say "we can start Monday" on a job with a 4-week normal lead time, ask why.
• Do you have backup capacity if a machine goes down? — For production runs, this matters. Multiple similar machines / cross-trained operators / partner shops for overflow.

Communication and relationship questions

"Who's my main contact?" Ideally one person — a shop manager or lead machinist — not a rotating cast. "How fast do you respond to a quote request?" 24 hours for routine, same-day for repeats — normal. "How do you handle a print revision mid-job?" Standard should be: stop, confirm the change with the customer, requote the delta. Avoid shops that quietly "figure it out."

"If something goes wrong, how do you communicate?" Look for a shop that calls immediately when there's a problem — not one that ships the bad part and hopes.

Frequently asked questions

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