What Medical Device Buyers Should Require from a Machining Supplier

By Invar Machining editorial team· Published September 26, 2026 · How we write these guides

Sourcing an Invar or Kovar part for a regulated medical device is not the same problem as sourcing the same part for an optical bench or a lab fixture. The material and the machining are identical either way, but the paperwork around the part, and who is responsible for verifying it, is not. This guide is written for the buyer, the device manufacturer’s own engineering or sourcing function, and covers what to ask a candidate shop and verify yourself before releasing a regulated-device drawing. This site matches buyers with independent machine shops. It does not audit or certify those shops, and it does not claim that itself or any matched shop holds FDA registration, FDA clearance, ISO 13485 certification or any other regulatory or quality credential. That verification is the buyer’s job, and this guide is meant to make it a concrete checklist rather than a guess.

Why this is the buyer’s responsibility, not the site’s

A machining shop supplies a component. The device manufacturer designs, tests, documents and takes regulatory responsibility for the finished device that component goes into, under its own quality system. That structure means the device manufacturer, not a machine shop and not a matching service, is the party accountable to a regulator for the finished product, and it is also the party best positioned to define what supplier evidence it actually needs, because that requirement depends on the device’s own risk classification and your company’s own quality procedures. A matching service can put a drawing in front of qualified machine shops. It cannot audit those shops on your behalf, and it should not be relied on as if it had.

This is not a disclaimer added for its own sake. A supplier verification step that a buyer skips because they assumed someone else, a directory, a matching site or the shop’s own marketing, had already done it is a common gap that shows up later during an internal audit or a regulatory inspection. Treating supplier qualification as your own team’s task from the first RFQ, rather than a step to revisit only if a part fails, is the cheaper path in every case we have seen.

Quality system documentation to request

Start with what quality system the shop operates under and whether its scope covers the work you need. The table lists what to ask for and what each answer tells you.

Document to request	What it tells you	What it does not tell you
Current certificate (ISO 9001, ISO 13485 or none)	Whether an accredited body has assessed the shop’s management system, and against which standard	Whether any specific part will conform, or how long the certificate has been continuously held
Certificate scope statement	Which processes and locations the certification actually covers	Anything about processes or sites outside that scope
Sample inspection report for a similar part	How the shop documents dimensional and material conformance in practice	Whether that level of rigor is applied consistently to every order
Process or work instruction summary for the relevant operation	Whether stress relief, cleaning or other steps you need are a defined step, not an afterthought	The competence of the specific operator on your job

Ask for the certificate itself and the scope statement, not just a logo on a website. A shop that machines parts at one location and assembles at another may hold a certificate that covers only one of the two. Certificates also carry an expiration and a surveillance audit schedule, so ask when the shop was last audited and by which accredited body, and check that the certificate is current rather than relying on a document dated several years ago.

Material traceability

For Invar and Kovar, where CTE and machinability vary by heat lot, traceability lets you connect a finished part back to its source material if a problem appears later. Ask whether the shop retains the mill certificate for each lot, whether its work orders record which lot went into which parts and how long those records are kept. Ask, too, what happens when the shop switches mills or distributors mid-program, since a change of source with no corresponding change in your documentation is exactly the gap that later makes a nonconformance investigation take weeks instead of days. Invar material certification covers what a mill certificate typically contains and how to read it, including how it should cite ASTM F1684 or the relevant sealing alloy spec. This is a machining and materials question, not a claim about the finished device’s own traceability record, which your own quality system builds separately using this supplier data as an input.

Change control and notification

A shop’s process, tooling or even its material source can change between orders without necessarily telling you, unless your purchase agreement or quality agreement requires notice. Ask specifically:

• Does the shop notify you before changing the mill or supplier for the raw material.
• Does the shop notify you before a significant process change, such as a different stress relief cycle or a new cleaning process for sealing parts.
• How does the shop handle a drawing revision, and does it confirm receipt and understanding of each revision before running production.

Invar engineering change requests covers how a drawing revision typically flows between buyer and shop, which is useful background for setting these expectations up front, in writing, before the first production order.

Second source readiness

Relying on a single shop for a critical Invar or Kovar part creates a single point of failure that has nothing to do with the shop’s quality system. If a shop closes a line, loses a key operator or has a bad quarter, you want a second qualified source already in place rather than starting cold. Invar second source qualification covers how to qualify a backup shop against the same drawing without duplicating your entire supplier verification process from scratch.

Worked example: comparing two candidate shops

Take a hypothetical buyer evaluating two shops for a Kovar seal ring destined for a Class II style device program. Shop A holds ISO 13485 with a scope covering machining and cleaning, provided a full material certificate history for the last twelve months of orders and answered the change notification questions in writing within a day. Shop B has no third-party certification, described an internal quality process verbally but could not produce a written procedure and did not have a clear answer on notifying the buyer of a material source change.

Factor	Shop A	Shop B
Certification	ISO 13485, scope confirmed	None
Material traceability	Full lot records for 12 months	Verbal description only
Change notification	Written process, confirmed in writing	Unclear
Price	Higher	Lower

This is a hypothetical comparison, not a real evaluation of any shop matched through this site. On the facts as stated, Shop A gives the buyer’s own quality system more to work with, at a higher price. A buyer with tight documentation requirements would likely need Shop B to close specific gaps in writing before use, or would use Shop A despite the cost difference. Neither outcome is dictated by this guide. The decision, and the responsibility for it, belongs to the buyer’s own quality function.

A short verification checklist

Before releasing a regulated-device drawing to a new machining supplier, confirm you have, in writing:

1. The shop’s current quality certificate, if any, and its scope statement.
2. A sample inspection report for a comparable part.
3. Confirmation of material traceability practice and record retention period.
4. A defined process for notifying you of material, process or drawing changes.
5. A named contact for quality questions, separate from the sales contact.
6. Your own internal sign-off that this documentation satisfies your company’s supplier qualification procedure.

None of this replaces your own supplier audit process if your quality system requires one. It is a starting checklist for the conversation, built around what buyers most often forget to ask until after a part has shipped. Related material and process specifics are in Kovar hermetic feedthrough machining for medical devices, Kovar seal ring machining for medical devices and Invar machining for diagnostic equipment components. The reference page of Invar and Kovar specifications lists the material standards a certificate should cite. Other considerations across the vertical are on the medical device manufacturing overview.

How the RFQ and matching process fits in

When you send an RFQ with the drawing, we match it with up to three shops that machine Invar and Kovar and that we understand cut these alloys for the industry your drawing indicates. That matching is based on capability and stated experience, not an audit of the shop’s quality system, and it does not substitute for the verification steps above. Each shop quotes you directly, and the supplier qualification decision, including what documentation you require before releasing production parts, remains yours to make.

Frequently asked questions

Reviewed against

• ASTM F1684, Standard Specification for Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications
• Wikipedia, ISO 13485

Values in this guide are typical handbook figures for planning. The mill certificate for your heat lot and the shop's quote for your geometry govern.

Keep reading

• Kovar Feedthroughs for Implantable Medical Electronics · Materials
• Kovar Seal Rings for Medical Device Hermetic Packages · Process
• Invar Parts for Diagnostic and Lab Equipment Manufacturers · Materials
• Second-Source Qualification: Requalifying an Invar Part at a New Shop · Choosing a Supplier

All choosing a supplier guides