How we write and maintain these guides
The guides on this site exist so that an engineer or buyer can write a better Invar RFQ and read a quote properly. This page says how they are made and what you can rely on.
Who writes them
The guides are written and maintained by the Invar Machining editorial team, the same people who read every RFQ and talk to the shops that quote them. We are not a machine shop and we do not sell material or tooling, so no guide promotes a product. Questions and corrections go to .
Where the numbers come from
Composition limits and property values come from the governing specifications, mainly ASTM F1684 for Invar 36 and Super Invar, ASTM F15 for Kovar and ASTM F30 for Alloy 42, and from published handbook data for iron-nickel alloys. Machining parameters are typical starting points from tooling practice for austenitic and nickel alloys. Heat treatment cycles are typical cycles of the kind found in aerospace process specifications. Every guide lists the sources it was checked against in a "Reviewed against" block at the end.
Typical, never promised
CTE values, tolerances, speeds and feeds, cycle temperatures and cost ranges are labelled typical. They are for planning. The mill certificate for your heat lot, the heat treatment your spec calls for and the quote from the shop that will cut your part are the numbers to design and buy against. Where a design depends on a property, we tell you to ask for measured data.
What we never publish
- Invented case studies, customer names, client counts or testimonials. Worked examples are labelled as hypothetical.
- Certifications we do not hold. We claim no ISO, AS9100 or other certification for this site, and a certification in a shop's profile is the shop's claim.
- Recommendations of a specific shop, mill or tool brand inside a guide.
- Claims that we machine anything. We match RFQs with shops. That is all we do.
How pages are updated
Each guide shows its published date and, once revised, its updated date. We review the reference tables when a cited specification is revised and we revise guides when readers or shops point out an error, when search data shows a question the guide does not answer, or when practice changes. Corrections are made in place and the updated date is changed.
Independence
Shops pay us for matched requests. Buyers pay nothing. No shop pays to be mentioned in a guide, and no guide is written to favour the shops that buy leads. The matching is done on alloy history, heat treatment access and part size, and the guides are written to help you judge any shop, including ones we have never spoken to.
Style
Plain language, short sentences, units on every number. We explain why something matters before we say what to do about it. If a guide reads like marketing, that is a defect and we would like to know.