DeTomaso Mailing List: March 2000, Message #47

	Dave is totally correct on this.  Many variables can affect the
readings but I guess if your not looking for super accurate readings
(0.001") it probably is OK to read (0.01-0.05").  To get a consistent
reading to 0.001" you normally need to have an assortment of contact
transducer, a very homogeneous coupling jell and a skilled operator. Also
you should never trust a supplied test specimen for calibration, I always
try to take a micrometer reading on an area of the component I want to test
and calibrate the US tester to that same spot.  Some US gages have factors
that you input for different materials but I have found that even within the
same material group you can have different echo characteristics, that is why
you always cal. to a mic'd area on the part. The other factor is transducer
selection you could have a transducer that works well with a cylinder bore
but that same transducer would not do a very good job on a radius of an
exhaust or intake port or an inside/outside radius.
The last thing I'll mention is if the US tester does not have a screen to
actually observe the echo pattern sometime you get a double echo, guess what
that means? Either there is an inclusion (pocket of dissimilar material) or
corrosion (brings up another point test specimen preparation).  A US gage
without a screen may report the largest echo or the first echo it
encounters????  
	Just something to think about, I think it is a good idea but the
gage has to have  very implicit instructions on it's use or there maybe some
problems.   

J.P. Buonamici
Body Process Engineering Supervisor
St. Thomas Assembly Plant
Hwy. #2 Talbotville, Ont.
Mailing : P.O. Box 2005 St Thomas, Ont. N5P 3W1
Ph.# (519) 637-5239 Fax. # -5125
E-mail: Jbuonami@Ford.com
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-----Original Message-----
From: Dave Aument [mailto:auments-dave@redrose.net]
Sent: Wednesday, March 01, 2000 8:03 PM
To: Multiple recipients of list
Subject: sonic tester


It sounds like a great idea, and before I continue please allow this
disclaimer, "I don't profess to be an expert" but there must be a learing
curve here as I'm sure there are many, many variables that come into play.
I have access to a TIG, MIG and stick welder but that doesn't make me a
great welder.


    MY .02  Dave