Proper Tool to Measure Wall Thickness (ISO 3611 - Micrometers)

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Dallen378

Trying to settle an internal debate here at my company. We are an aluminum extrusion company, and without having purchased the standard for ISO 3611:2010 regarding micrometers for external measurements, there is some debate as to the proper mic to be used to measure a flat wall.

Myself and another gentleman believe a ball-mic to be the most accurate as it will detect high or low spots in wall thickness that have tight tolerances.

2 other gentlemen (who both came from the same company prior to ours) believe it to be a flat-mic.

Now we deal with wall thickness tolerances of +/- .001 regularly, but that isn't necessary for the argument.

So would just like a little feedback from the forum. And perhaps if anyone has knowledge of the spec 3611:2010 and what it may state.

I am new to the forum and am excited at how much I have already discovered from reading so many threads that are relevant to my needs!!

Thanks in advance
 

Ronen E

Problem Solver
Moderator
A ball micrometer will give a spot reading while a flat one will indicate the maximum over its face surface. Hence a flat one will always show an equal or greater result, if applied to the same place. Which one to pick depends on what you're trying to establish.

Sorry but I don't know ISO 3611.
 

David-D

Involved In Discussions
Application is going to have a big effect on which you want to use.

If what you are measuring is the outside diameter of the entire tube, then I would lean towards the flat face micrometer as I'd expect it to more readily be able to be placed correctly and kept perpendicular to the axis of the tube. if you actually are looking to measure the wall thickness, you really need to have a curved anvil to touche the inside wall, otherwise the curvature of the concave surface will not properly contact a flat anvil and youll get a measurement which is slightly too large.

David
 
D

Dallen378

Application is going to have a big effect on which you want to use.

If what you are measuring is the outside diameter of the entire tube, then I would lean towards the flat face micrometer as I'd expect it to more readily be able to be placed correctly and kept perpendicular to the axis of the tube. if you actually are looking to measure the wall thickness, you really need to have a curved anvil to touche the inside wall, otherwise the curvature of the concave surface will not properly contact a flat anvil and youll get a measurement which is slightly too large.

David

The ball-mic is what myself and my die shop supervisor agreed was the proper tool. For this exact reason. Still would be interested to see what the ISO 3611 standard says. If we end up purchasing for our records, I will come back and share what it says.
 
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AeroSteve

I can see benifits to both, the ball mic will always give the lower reading, however, I can imagine a sennario where the corner of the wall is not clean and square (due to example wear in the die) in which case, the flat mic would be better at identifying this problem. So, my vote would be actually be to use (or to at least have available) both micrometers. Good luck!
 

Ron Rompen

Trusted Information Resource
The best tool that I have found for measuring wall thickness in small diameter tubing is a uni-mic (https://www.all-spec.com/Catalog/Te...17-107-65737?gclid=CKm517vngtECFQOAaQodD5kHRw)
The anvil of the mic can hold a gauge pin, so that you get a single point of contact on the inner wall of the tube, while the flat anvil of the opposite side ensures you get the maximum point-to-point measurement. Since the gauge pin can be removed, the mic is very versatile.
If you are making 'large' tube then a double-ball (or possibly even a single ball) micrometer might also be appropriate.
 
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