How we vet machine shops before they see your RFQ
We are a matching service, not a machine shop. Before a shop is added to our matching pool, or matched with a specific RFQ, it has to answer the same questions a careful buyer would ask. This page is that checklist.
Why this exists
"We can machine Invar" describes thousands of shops, since the mills and lathes involved are the same ones used for stainless. The gap that matters is in the process around the cutting, not the equipment list: where stress relief happens, how thin sections are fixtured, and at what temperature the part is measured. A shop that cannot answer these specifically does not get matched with a thermally critical request, no matter how capable it is on general work.
What we check
| Question | Good answer | Red flag |
|---|---|---|
| Which low-expansion alloys, and how recently | Names Invar 36, Super Invar, Kovar or Alloy 42 specifically, with rough lot counts from the last 12 months | "We can source any material" |
| Where stress relief happens | In-house furnace or a named contracted heat treater | "We can add that if you need it" |
| How the cycle is chosen | From the drawing, the governing spec, or a record on similar parts | One generic cycle used for everything |
| How thin sections are fixtured | Low-force or vacuum fixturing, alternating sides, a final skim after stress relief | "Carefully" |
| Measurement temperature | States 20 °C after a soak, on the inspection report | No stated temperature |
| Paperwork that ships with the part | Mill cert by default, CTE data and full reports available on request | Certs "if required", no process for it |
This is the same checklist a buyer can run themselves, laid out in full in how to find a machine shop with real Invar experience. We run it before your drawing ever reaches a shop; you can run it again once you are talking to one directly.
What we do not check
We do not audit a shop's facility, verify a certification, or inspect its equipment in person. What we check is whether a shop can describe its own process specifically enough to have actually run it: a named alloy and lot, a real cycle, a stated inspection temperature. That is a screen for recent, relevant experience, not a certification or a guarantee of quality on your specific part.
What happens after a shop passes
A shop that answers these questions specifically is added to our pool for the alloys and part types it described. When an RFQ comes in, we match it against alloy, tolerance, heat treatment and size, not against who asked to be matched next, and send it to up to 3 shops. See how the matching itself works for the RFQ side of this process.
Do you audit or visit the shops you match?
No. This is a screening conversation, not a facility audit or a certification. We ask the questions on this page before a shop is added to our matching pool and again in the context of your specific RFQ, and we check their answers for the specificity that only comes from having actually run the process. We do not inspect equipment or verify claims on site.
What disqualifies a shop?
Vague or generic answers to the alloy, heat treatment or measurement questions on this page. A shop that cannot name a recent Invar lot, describe a stress relief cycle, or say at what temperature it inspects does not get matched with a thermally critical RFQ, regardless of its general CNC capability.
Does a shop need a certification to be matched?
No. We do not require or verify ISO, AS9100 or any other certification, and we do not claim any ourselves. A certification named in a shop’s profile is the shop’s own claim, not something we have checked. If a certification matters for your part, ask the shop directly and ask for the certificate.
Does this replace my own vetting?
No. Matching narrows the field to shops that answered these questions specifically, but the order and the relationship are between you and the shop. Our buyer guide on <a href="/blog/find-invar-machine-shop/">finding a shop with real Invar experience</a> gives you the same questions to ask directly once you are talking to a shop.