Sonic tester "how to"?

[fairlaniac]

I recently picked up a Digi-Sonic 502 Ultrasonic thickness gauge. I bought it thinking I might be able to sonic check my own blocks. I'm trying to figure out how to use this thing. Has anyone ever used one or can someone help me fumble through it? Maybe this unit cannot do what I want it to do? I have the manual but I think you need to have an idea what you're doing to begin with in order to use it? Both transducer that came with it have a flat face, to check cylinders does it need to be radiused?

Thanks!
Doug

[fairlaniac]

Pics

[jayb]

The sonic testers I've seen have indeed had a radiused face, so that the center of the probe fits right up against the cylinder bore.  I friend of mine bought one with a flat face and had it machined into a radius, but it looked different than the one in your photos, and I don't know if yours could be modified in the same way.  Other than that, the one key thing about using the sonic checkers is that they need to be calibrated properly to give accurate results.  I've seen several sets of sonic check data that don't pass the smell test, and the probable cause is that the checker is out of calibration.  To check calibration you need to find a part of the block, like down by the oil pan rail, where you can measure the thickness with a micrometer.  Then you can check the same spot with your sonic checker, and adjust the calibration until you get the same thickness.

Hope that helps - Jay

[Barry_R]

Radius face.  CLEAN block and bore.  I calibrate against the front "china wall" below where the intake sits - nice flat and machined surface there that you can decently measure.

[fairlaniac]

Do you think it is possible to radius the face of the probe? It is about 3/4" diameter with what looks like a pink plastic face in the center with a stainless outer ring. It's the only probe I have and cannot find a source for new probes. I figured out how to use it and recalibrate it. It has it's own recalibrating system with built in test block. I've played with many thickness of flat over the weekend and it matches what I mic with the micrometer. The probe has a twist lock fitting. Do all or other brands use the twist lock fitting? I wonder if I got a different maker probe if it would work?

Thanks,

[jayb]

If the face is plastic I'll bet you could radius it and have it work.  The sensor element is some kind of a metal element in the center of the probe; on my friend's version, you can actually see it through the plastic.  When he had his radiused they just cut the plastic and outer ring, and left the center plastic intact over the metal sensor element.

[Barry_R]

I think mine is some sort of pinkish ceramic - kinda grindable though

[fairlaniac]

I think mine is a ceramic material now that I look closer. After I laid out the probe drawn in CAD with a 4.26 bore it looks like I need to start my radius up from the flat about .033 and taper towards the middle. I'd assume I should use a finer grinding wheel as a coarse wheel could leave depressions of .010? Here is what my probe looks like.

[matt souders]

So what is the minium thickness for the walls. I would imagine there being a number that would be a good average for any engine make or model. I know for a more racing type engine you might want a thicker. But what would you guys say the average would be.

[hotrodfeguy]

Depends what side you are talking. You would want more meat on the thrust sides, that's where the load is. And in between cyl its not real big of a deal, offset bore can be done as well if one side has more to spare than the other. Is it a MARINE block with the re-enforced corners? Are you filling the block? These are all factors. And the bottom line is how much do you want to roll the dice and what are you willing to live with.

[machoneman]

See Barry's Forum reply...I had saved this one as it's a keeper! 

http://www.network54.com/Forum/74182/thread/1323361552/Identifying+a+late+model+390+block.