Steel tubing thickness testing

Maybe I didn't look in the correct place(s) but I can't find much apex info on handheld steel thickness testers. Looks like I may be given a S2 Tiga project. I am interested in a tester to assure myself the tubing in the car is within thickness tolerance as original. Other than my obvious paranoia I often wondered how all these old FF that has water going thru frame tubes have survived this long
What I am looking for is hand held, can set high and low limit alarms AND referal from someone who actually used one not someone who necessarily sells them. Lookinf for brand etc. Something reliable not necessarily cheap. Not much into borrowing just saying. Jim.

Jim,

All else failing, drill a hole in a low stress area, measure the OD and measure from the outside through the hole witht he dpeeth portion of your calipers. Subtract one from the other and you have the wall thickness.

Like you have to do for a SCCA roll bar wall thickness verification.

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Originally Posted by Westroc

Maybe I didn't look in the correct place(s) but I can't find much apex info on handheld steel thickness testers. Looks like I may be given a S2 Tiga project. I am interested in a tester to assure myself the tubing in the car is within thickness tolerance as original. Other than my obvious paranoia I often wondered how all these old FF that has water going thru frame tubes have survived this long
What I am looking for is hand held, can set high and low limit alarms AND referal from someone who actually used one not someone who necessarily sells them. Lookinf for brand etc. Something reliable not necessarily cheap. Not much into borrowing just saying. Jim.

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I did a substantial amount of UT testing for several of my employers. We had some very sophisticated ones for taking many measurements along a series of piping runs that would record by location by either bar code or RFID. Others were very simple ones for pipe and tube thickness verification. The one that I found for my engineering techs doing random field and shop testing was the Olympus 27MG with a 7.5mm transducer. It will measure down to 0.020". We trained them to also check calibration with a standard gage to reduce the chance of measurement errors. Surface must be clean and free of paint or other coatings. YMMV

Like Dan says, a good ultrasonic thickness tester will do this job. They are available from a multitude of sources, go on eBay and find a good one. The one I own cost about $1500 a decade or so ago. I bought it specifically for doing frame inspections as you mention; we check the frame at 2” increments at 12/3/6/9 o’clock on the tube, and if we have a spot that is deemed too thin we will check closer to get an idea of how bad or how large the thin spot is. Over the years we have had a few FB/FF/FJr frames that needed top or bottom rail replacement due to this test.

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Originally Posted by teamwisconsin

Like Dan says, a good ultrasonic thickness tester will do this job. They are available from a multitude of sources, go on eBay and find a good one. The one I own cost about $1500 a decade or so ago. I bought it specifically for doing frame inspections as you mention; we check the frame at 2” increments at 12/3/6/9 o’clock on the tube, and if we have a spot that is deemed too thin we will check closer to get an idea of how bad or how large the thin spot is. Over the years we have had a few FB/FF/FJr frames that needed top or bottom rail replacement due to this test.

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Have you done calibration checks on known-thickness material? What sort of accuracy and repeatability do you get? thx

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Originally Posted by Lotus7

Have you done calibration checks on known-thickness material? What sort of accuracy and repeatability do you get? thx

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I always buy a calibration standard with each instrument and perform a calibration check with each use. Accuracy is good with smooth ID tube. Accuracy will vary by transducer and condition of tubing bore. Most transducers for thin samples Quote within 0.010” but with practice and care to 0.006”. We practiced frequently with sample pieces of known thickness for thin wall exchanger tubes.

I hope there is more replies but to each who have thank you. Been around apex since the very beginning before the Carters ever bought their FE which to most on this site is a long time ago. I personally think this topic needs more light as most cars running today need this done really. I mean a /95 VD will be 30 years old pretty soon. Jim.

I noticed that Cal Club Tech people used a Dakota Ultrasonics meter

https://dakotaultrasonics.com

Some factors that can affect the accuracy of the readings:

• Temperature - make sure the part being tested and the calibration standard are within 25 deg. F (velocity changes with temperature and ultrasonic thickness testing is really just a case of measuring time, which is affected by velocity).
• Keep in mind you need to test the same type of material as the calibration standard, if you were going to measure aluminum and calibrated on carbon steel it would be off because different materials have different velocities. Just mentioning should someone want to get creative and measure something other than their steel tubing.
• The transducers will invariably be a dual-element, it's best to put the line (cross-talk barrier) perpendicular to the tube axis so that both crystals are similarly in contact with the tubing.
• Even if doing the above, the small diameter of tubing could affect accuracy. If I was wanting to be as accurate as possible I would want a calibration standard of similar diameter as has been previously mentioned.
• The dual-element transducer also has a slight amount of inherent non-linearity if measuring thin objects (<0.125") and the calibration standard is not a similar thickness. This non-linearity increases the thinner you get.
• It's best to have calibration standard thicknesses both above and below the measured thickness.
• As mentioned, clean the part of any paint (there are techniques to compensate for paint, but too much to go into here).

Most of the above (paint and material types being the exceptions) would generally have a minor or no perceptipal effect, just things to keep in mind if quoting a degree of accuracy.

Thanks again for comments. My goal here is to measure every tube on a S2. Probably with exception of nose and body "extensions". All of the tubes in the main tub for sure. Probably in multiple places. I want to know what I have before I start a ground up. Frankly being a bit lazy but with the number of places I intend to do I am less thrilled with having to remove paint to do it. On the other hand I'll probably sandblast it anyway then measure it.

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Originally Posted by Westroc

Thanks again for comments. My goal here is to measure every tube on a S2. Probably with exception of nose and body "extensions". All of the tubes in the main tub for sure. Probably in multiple places. I want to know what I have before I start a ground up. Frankly being a bit lazy but with the number of places I intend to do I am less thrilled with having to remove paint to do it. On the other hand I'll probably sandblast it anyway then measure it.

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Epoxy primer can do a nice job hiding corrosion. These tubes are probably 0.035 -0.049”.
Consider sand/media blasting, magnifying glass and spring loaded center punch.

I use a couple different relatively inexpensive PhaseII ultrasonic thikness testers at work. These would be perfect for what you need. They have a calibration block built onto the meter body so they get verified every time they are used.

If this is a one time deal check local fab shops and see if they have one. If you remove the paint and mark the areas of greatest concern they can probably test all of them in less than an hour. My guess is you get out of there for $100 if you make it easy enough for them. If I were you I'd give them a nice new sharpie marker and tell them to write the measurements right on the tubes as they take them so you can review later.

Various construction codes require testing of steel plate for laminations. Also piping/ vessel shops use them for corrosion and thickness verification. Any decent size shop around probably has one.

Edit: our newest one can shoot through paint. But in my experience it is less than ideally accurate in that mode. Ymmv. You only need to grind a dime sized spot clean to get a reading.

Edit 2: if you use an aggressive media like crushed glass or coarse black beauty, it can make the surface too rough to easily couple and get a reading. If you go that route use fine ground garnet or glass beads