Every dimension on your drawing is a promise. Coordinate Measuring Machine (CMM) inspection is how we prove that promise was kept. This article explains how CMM measurement works, what the reports we ship with your parts mean, and which inspection level to order for your project.
What a CMM actually does
A CMM moves a calibrated touch probe (or laser/optical sensor) across the part, recording thousands of XYZ coordinate points. Software fits geometric elements — planes, cylinders, circles — to those points and compares the result against the nominal CAD model or drawing dimensions. Modern CMMs in a temperature-controlled room resolve measurements to a few microns, which is why they are the reference standard for verifying tolerances like ±0.005mm.
Reading the inspection report
Our standard dimensional report lists each measured characteristic with: the nominal value from your drawing, the tolerance band, the actual measured value, the deviation, and a pass/fail flag. Bubble-numbered drawings tie each report line to a specific callout, so you can verify any feature in seconds.
GD&T: beyond simple dimensions
Geometric Dimensioning and Tolerancing controls form and relationships, not just size. The most common callouts we verify:
| Symbol | Control | Typical use |
|---|---|---|
| Flatness | Surface form | Sealing faces, cold plates |
| Position | Hole location vs. datums | Bolt patterns, dowel holes |
| Perpendicularity | 90° relationships | Mounting faces, bores |
| Concentricity / runout | Rotational alignment | Shafts, turned parts |
| Profile of a surface | Complex 3D contours | 5-axis aerospace surfaces |
Inspection levels we offer
Standard inspection
Included with every order: critical dimensions checked on a sampling plan, with a dimensional report on request.
First Article Inspection (FAI)
Full measurement of every drawing characteristic on the first production piece, reported in AS9102-style format. Standard for aerospace and medical work, and recommended before any production run.
100% / CpK reporting
For safety-critical features we measure every part, or measure a statistical sample and report process capability (CpK), giving you evidence the process — not just the part — is in control. This is routine under our IATF16949 automotive quality system.
Traceability
Each report is tied to the material certificate, machine, operator, and calibration records for the instruments used. If a question arises a year from now, we can reconstruct exactly how your part was made and measured. See our quality & certifications page for the full system.
How to order the right level
Prototypes: standard inspection is usually enough. Pre-production: order an FAI so the drawing, process, and expectations are aligned before volume. Production: FAI plus in-process sampling; add CpK reporting for critical characteristics. Just note the requirement in your quote request — inspection is priced transparently as a line item.
