A CMM report can run to thirty pages for a single part. You do not need to read all of it. You need to know where the answer is.

The three columns that matter

Every line lists a feature with its nominal value from the drawing, the measured value and the deviation between them. Beside those sits the tolerance band. If the deviation is inside the band, the feature passes.

Look at where it sits in the band

A feature that passes at 95% of its tolerance is a warning. The next batch, with a slightly worn tool, may not pass. Good reports show a bar for each feature so you can see this at a glance.

Datums first

All position results depend on how the part was aligned. Check that the datums in the report are the datums on your drawing. If they are not, the numbers describe a different part.

What to ask your supplier

• Was the part measured at 20 °C?
• How many parts from the batch were measured?
• Is the report tied to a serial or batch number?

A report is only as good as the question it answers. Tell us which features matter to your assembly and we measure those on every part.

First article and after

The first article report covers every dimension on the drawing. Batch reports after it usually cover the critical features only. Agree that list once, in writing, and both sides save time on every order.