Wear is a geometry problem. If you can capture the surface now and compare it to CAD — or to a scan from last overhaul — you get a map of material loss, not a single micrometer reading on a convenient spot.
How we measure wear
- Scan the current condition (lab or on-site).
- Align to CAD, to a master part, or to a previous scan of this serial number.
- Report signed deviation, often as a colormap plus sections through the high-wear zones.
Coatings and plating work the same way with the sign flipped: build-up instead of loss. The method still depends on a stable alignment. A best-fit of a badly worn part can hide the wear you came to measure; we call that out and use datums or unworn regions when they exist.
When a caliper is enough
If the question is “is this journal still above the service limit at one plane,” a CMM or even a qualified bench method may be cheaper. Scan-based wear analysis earns its keep on freeform parts, unknown wear patterns, and arguments that have to be shown, not asserted.
Metrology programs and quote requests should mention whether you have a baseline scan or only CAD.
— Bolton Works