Ask “how do I measure wall thickness?” and you’ll get two different answers: an ultrasonic tester or a mechanical gage. Both are right — for different jobs. Here’s the honest comparison.
Where ultrasonic wins
- One-sided access. If you can only touch the outside (pipelines in service, tanks, hulls), ultrasonic is the only option.
- Very thick sections. UT handles inches of steel.
Where mechanical wins
- No calibration to the material. UT readings depend on sound velocity — wrong alloy setting, wrong answer. A dial gage reads the wall directly, on any material: steel, aluminum, plastic, rubber, composite.
- Curved and cast surfaces. UT couplant and probe alignment get fussy on small radii and rough as-cast walls. Ball contacts don’t care.
- Speed on the shop floor. Squeeze, read, next part. No couplant, no zeroing blocks, no interpretation.
- Finding the true minimum. Sliding a mechanical gage lets you feel the thin spot. Dyer gages are built for exactly this scanning motion.
The rule of thumb
If you can reach both sides of the wall, mechanical is faster, cheaper, and more foolproof. If you can’t, use ultrasonic.
Mechanical options by job
- General castings and machined parts: 301 Series direct reading min-wall gages
- Digital readout / SPC output: 653 Series electronic thickness gages
- Deep reach into tubes and shells: 334 Series long reach gages
- Soft, thick, or honeycomb materials: 306 Series
Not sure which side of the line your part falls on? contact Dyer Gage or call the gage hotline at 1-800-631-3333 with your print and material — you’ll get a straight answer, even if that answer is “use ultrasonic.”