Bottom of cooling jacket: Not super thick

moper said
A note - if the surface of the media being tested is "as cast", your results may vary... Most transducers made for a curved surface will not sit very well on an as-cast finish. I would suggest if you tested on the cast finish you use a bur or sanding roll and smooth it out. Then re-test. The coiupling gel is not "filler". The transducer halves have to contact the surface properly or the reading will be suspect.

My big thing here was that I had the impression that this area was something like .5" thick minimum and so grinding with abandon would not be a worry.... does not look like that is the case LOL!

Roger on the above.... I use white lithium grease as a 'gel'.... seems to couple well, and I do repeated measurements. The sonic tester I have has an indicator on the screen when it is sensing a well-defined reflection (which implies good coupling). I also used old style curved calipers, like pictured below, to reach around the casting and confirm the sonic measurements. The corner thickness measurement was done in this way as I would not expect the sonic tester to be at all accurate there. But I still just may do as you suggested in one place with smoothing it out.

If I had a junk block I would get out the portable band saw and slice it up to be sure and take pix.

3 Inch Leg, Spring Joint, Steel, Powder 62393863 - MSC