Sourcing Custom Invar Parts for Research Lab Instruments

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

A drawing that comes out of a national lab or a university machine shop request rarely looks like an industrial print. It might be a SolidWorks sketch with a few dimensions and no title block, a hand-annotated PDF of a CAD model or a description in an email that says roughly what the part needs to do and leaves the geometry to the shop’s judgment. None of that means the part is any less real or any less demanding to machine correctly. It means the procurement process around it looks different from an industrial buyer’s, and a shop that understands that difference quotes it better and faster than one that expects an industrial drawing every time. This guide covers how research lab purchasing actually works, what a shop needs even from an informal drawing and how to write an RFQ that gets you a useful quote despite a drawing that would not pass a formal industrial review.

Why research lab procurement looks different

A few realities shape almost every academic or national lab RFQ for Invar hardware, and naming them upfront saves a round of back-and-forth later.

The person writing the drawing is often the person who will use the part. A grad student, postdoc or staff scientist designing a custom sample stage, a fixture for a beamline experiment or a mount for a lab instrument is usually also the end user, not a professional mechanical designer working from a formal spec. The design intent is almost always sound. The drawing notation, tolerancing convention and material callout that an industrial buyer’s engineering department would add by default are often simply not there, because nobody on the team does that work full time.

Purchase orders follow grant and fiscal year cycles, not a steady procurement calendar. Funding can arrive in a lump tied to a grant’s start date, get harder to spend as a fiscal year end approaches or depend on a purchase order that has to route through a university or lab’s procurement office before it reaches a supplier. A shop used to steady industrial ordering can misread a slow PO process as disinterest when it is actually an institutional timing issue.

The real deadline is often an event, not a date on the PO. Beamtime at a shared facility, a conference demonstration or the end of a grant period drives urgency more directly than a generic “as soon as possible.” Naming the actual event helps a shop judge how firm the date is and whether it is worth prioritizing.

Quantity is almost always low. One fixture, one mount, occasionally a handful for a multi-station experiment. This is covered in more general terms in prototype versus production Invar machining and in Invar 36 machining, but it is worth restating here: low quantity is the normal case for this buyer, not an exception the shop needs to be talked into accepting.

None of this is a complaint about how research procurement works. A shop that machines Invar for industrial buyers all week and picks up an occasional university order benefits from understanding these patterns rather than judging the RFQ against an industrial yardstick it was never trying to meet. The alloy itself, an iron-nickel alloy whose low expansion was first put to practical use in scientific instruments over a century ago, is described in general terms on Wikipedia’s entry on Invar, a useful primer for anyone on a research team who has inherited “just get it made in Invar” as an instruction without much more context.

What an informal drawing is often missing

The table lists what a typical research lab sketch has, next to what a formal industrial drawing would add, and why the gap matters to a shop trying to quote accurately.

Element	Common in a research sketch	Common in a formal industrial drawing	Why it matters to the shop
Overall geometry	Usually clear, often a 3D model	Clear, with orthographic views	Sets the machining approach and fixturing
Critical dimensions flagged	Rarely marked	Toleranced individually, often with GD&T	Without it, the shop must ask or guess which dimensions actually matter
Material and spec	Sometimes just “Invar”	Full spec, for example “Invar 36 per ASTM F1684”	Trade names vary; the spec avoids ordering the wrong alloy or temper
Surface finish	Rarely specified	Called out per surface	Affects both cost and whether a critical mounting face is protected
Heat treatment or stress relief	Rarely mentioned	Specified as a process step	Determines whether the part needs a furnace cycle for stability
Quantity and timeline	Often in an email, not on the drawing	On the purchase order and drawing	Shapes how the shop plans material and scheduling

None of the gaps in the left column make a part unbuildable. They make it a part the shop has to ask questions about, which is exactly what a well-written RFQ can answer before the shop ever has to ask.

How to write an RFQ that fills the gaps

You do not need CAD skills or GD&T training to give a shop what it needs. A short paragraph or a bulleted list alongside your sketch or model covers most of it:

1. State the material and spec explicitly, even if your drawing just says “Invar.” Write “Invar 36, ASTM F1684” or “Kovar, ASTM F15” so the shop orders the right alloy, not a guess based on the name alone. The Invar specs reference has the exact numbers if you are not sure which alloy fits your application.
2. Say in plain words which dimensions actually matter. “The two mounting holes need to be within 0.05 mm of each other, everything else is not critical” tells a shop more than a drawing with no tolerances at all, and it lets the shop quote a realistic price instead of pricing every dimension as if it were critical.
3. Describe what the part does, not just what it looks like. A sentence like “this holds a sample at cryogenic temperature and needs to stay flat to within 0.02 mm” gives the shop context a bare geometry cannot, and it often prompts a useful suggestion you would not have thought to ask for.
4. Give your real quantity and timeline, including the reason for the date. “One part, needed before a beamtime run starting in six weeks” is more useful to a shop than “ASAP.”
5. Say whether you are the end user and whether follow-up questions can go to you directly. Research RFQs often move faster when the shop can ask the actual designer a quick question instead of routing through a purchasing office.

The full checklist for what belongs on any Invar RFQ, research or industrial, is in our RFQ drawing checklist.

A hypothetical worked example

A postdoc needs a custom Invar 36 bracket to hold an optical reference cell inside an existing instrument enclosure, sketched in a CAD model with the overall shape and hole positions but no title block, no tolerances and no material spec beyond “low expansion metal, like what’s in the old bracket.”

Written as an RFQ, this becomes: “Invar 36, ASTM F1684 to match an existing bracket. The two mounting holes and the cell seat need to hold position within about 0.03 mm relative to each other; the outer profile just needs to clear the enclosure with a couple millimeters of margin. Quantity is one, needed within four weeks for a scheduled measurement run.” That single paragraph, alongside the sketch, gives a shop everything it needs to quote accurately: alloy, the dimensions that matter, a workable tolerance and a real deadline with its reason attached. The shop can now ask one or two follow-up questions instead of a long list, and can tell the postdoc honestly whether four weeks is realistic once material lead time is factored in.

This example is illustrative of a common pattern, not a specific project.

Handling IP, cost and low quantity honestly

Two things come up often enough in academic and national lab RFQs that they are worth addressing directly rather than assuming. First, if your work involves export control, a pending patent or a non-disclosure requirement before sharing the drawing, say so at the start; our NDA and IP protection guide covers what a shop can reasonably agree to and what usually is not workable for a one-off job. Second, a single Invar part carries the same setup and fixturing cost a shop would spend on part one of a production run, so the per-part price looks higher than a catalog item; our minimum order quantity guide explains why that is normal rather than a sign of an inflated quote.

See our industry overview for scientific instruments, research labs and accelerator facilities for other hardware categories common in this space.

Getting a quote

You do not need a perfect drawing to get a useful quote. Send your sketch or model through our RFQ form along with the plain-language notes described above, and we match it with up to three shops that are comfortable working from a research-style drawing and used to the quantities and timelines this kind of project actually runs on.

Frequently asked questions

Reviewed against

• ASTM F1684, Iron-Nickel and Iron-Nickel-Cobalt Alloys for Low Thermal Expansion Applications
• Invar, Wikipedia

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

• What to Include on an Invar RFQ: A Drawing Checklist · Choosing a Supplier
• Prototype vs Production Invar Machining: What Changes · Cost
• Minimum Order Quantities and Scrap Rates on Small Invar Batches · Cost
• NDA and IP Protection When Sending an Invar Drawing Overseas · Choosing a Supplier

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