"oldjag" wrote in message
ups.com...
I've seen several low cost import ultrasonic thickness testers on
Ebay. I'm wondering if they could be used to measure engine cylinder
wall thickness. They cover the thickness range, but all seem to have
flat probe tips. A 3/8" diam. flat probe tip inside a 4" bore would
have ~ 0.009" clearance at its mid point, and I'm concerned this might
prevent coupling even with glycerin or silicone gel. Anyone have any
experience with this situation?


These things get used for inspecting old steam boilers (for which they are
an absolute Godsend...). There is often at least 0.01 roughness in the
surface. A smear of Vaseline seems to work. On the other hand, it depends
on the degree of accuracy you need. For a boiler, an error of a couple
hundredths is not a problem. If you are expecting 0.325 and get 0.297,
you're probably quite happy. But if you get 0.082, you have a big
water-cooker you don't dare put a fire in...

Jerry