Guides / Process
Measuring a Ceramic Part: What the Report Should Actually Contain
August 10, 2026
A ceramic part is inspected differently from a metal part in three ways: the material is harder than the probe, the features are more fragile than the fixture and the surface condition carries more of the function. A shop that measures ceramic every week has habits that a general metrology room does not.
Dimensional measurement
CMM is the workhorse for most geometry. Two ceramic specific notes:
- Probe force must be low. A standard touch force that is harmless on steel can chip a sharp ceramic edge, and the chip becomes both a measurement error and a crack origin
- Ruby probe tips wear against hard ceramics, especially silicon carbide, so calibration intervals need to be shorter than on a metal part
Air gauges and plug gauges are fast and reliable for production bores, but a plug gauge on a tight ceramic bore can score the part. Plain gauges are used with care and often reserved for go and no go.
Optical and vision systems avoid contact entirely and suit thin, delicate or small features. For edge and profile inspection they are usually the better answer.
Flatness and surface
Optical flats under monochromatic light give a fast, cheap flatness read on small faces by counting interference bands. Larger or tighter work moves to interferometry.
Profilometry gives Ra and the rest of the roughness parameters. On a ceramic part this is worth having on the report, because surface condition relates directly to strength, as covered in how diamond grinding works.
Visual inspection under magnification is not optional. Edge chips, grinding burn and handling damage are found here or not at all. Agree an acceptance standard for chip size in advance, because “no chips” is not a real specification on a brittle material.
Material verification
The blank carries most of the material risk, so a good report starts before machining.
- Material certificate from the blank supplier: grade, purity, density, lot
- Density check, usually by the Archimedes method, when density is a specified requirement
- Grain size, on a polished section, for parts where it was specified
- Hardness, sometimes, although a Vickers indent leaves damage and is done on a sample rather than the part
For critical assemblies it is worth agreeing whether the certificate follows the lot or the individual part.
Internal defects
Porosity, inclusions and firing cracks do not show on the outside. For critical parts:
- X-ray or CT finds voids and inclusions without touching the part
- Ultrasonic inspection is used in some industries, although coupling to a rough surface is awkward
- Proof loading is sometimes the practical answer: load the part to a defined level and accept the survivors
Dye penetrant is generally avoided. It contaminates surfaces that need to be clean and can be drawn into surface connected porosity.
What to ask for on the RFQ
- A dimensional report on all toleranced features for the first article
- The flatness and finish measurements, with the method stated
- The material certificate for the blank
- A stated acceptance level for edge chips
- Sample based reporting for production quantities, with the sampling plan agreed up front
If the part is medical or semiconductor, add cleanliness and packing to the same list. Those are covered in ceramic parts in semiconductor equipment and zirconia parts for medical and dental work.
What an evasive answer sounds like
“We inspect everything” is not an inspection plan. Ask which equipment, which features, how often and what the report looks like. A shop that measures ceramic daily will answer in specifics, and that answer is one of the better signals you will get about them. More on that in how to qualify a ceramic machining shop.
To agree what to measure on the first parts, see ceramic first article inspection.
Send your drawing and we match it with up to 3 shops that own the inspection your part needs. Reply within 24 business hours.
Frequently asked questions
Can a normal CMM measure a ceramic part?
Yes, with care. Probe force has to be low enough not to chip a sharp feature and probe tips wear against hard ceramics, so calibration frequency matters. Non contact methods are often better for delicate features.
What should a first article report include?
Every dimension with a tolerance, the flatness and finish callouts, the material certificate for the blank, the measurement method used and the equipment identification. Anything as fired should be recorded as measured rather than accepted silently.
How do you inspect for cracks in ceramic?
Visual inspection under magnification catches edge chips. Internal defects need X-ray or CT for critical parts, and dye penetrant is not generally used because it contaminates porous or sensitive surfaces.
Need a quote for this part?
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