Metal expansion question

Aug 28, 2021 Last reply: 4 years ago 7 Replies

So I've got this metal bar (mild steel) and it's flat and 0.19" thick. Well, it *was* 0.19" until I measured it today and now it's put on an extra 9.5 thou which I can only attribute to the weather. I'm guessing I probably originally measured it at 10C and today it's 20C. But would



10 degrees C really make that much difference? I trimmed it down from
0.2" to make a shim and this extra few thou is really buggering things up.

Ta.



Dave Dagenham, UK


Finger trouble. I reckon it should have expanded around 0.02 thou. Assuming 10 degrees and a k of 12.5e-6/deg C

I'm not much good with inches and thou any more, particularly when mixed with degrees C. But:

The coefficient of thermal expansion of steel is around 10^-5 per degree C.

You raised the temperature by 10C, so your shim increased by 10 ^-4 (one-ten-thousandth) of it's original thickness, ie it increased by a fraction of a thou due to the temperature increase.

The original thickness was 190 thou, and that should have increased to

190.2 thou due to the temperature increase.

At least, I think that's correct. :)

I knew that was wrong! 190.02, not 190.2.

Same.

Dave,

Dagenham, UK

He may have been asking who made the measurements? ;)

HAHAHAHAHAHAHA!!!

Nice one. ;->

Dave,

Dagenham, UK

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