It happens that John Williamson formulated :
Harry Bloomfield wrote:
Could someone kindly provide me with the figures for the loading at which a
6mm ordinary mild steel rod will begin to stretch and one at which it will
break please, assuming room temperature? An answer in kilogrammes would be
good, just to settle an argument.

It will start stretching under *any* load, linear(ish) up to about 15% at
about four tons, and it will snap at just over 5 tons. A lot depends on the
end fastenings, though, as welding it to something will have an unpredictable
result on the strength of the bit affected by heat, and the same goes for
ultimate srength. Cutting a thread so you can tighten it up with a nut will
reduce the strength by a lot, depending on the thread form. Strongest is hot
rolled Whitworth, as it shouldn't have the sharp, stress raising, corners of
a cut thread.

Brilliant, thanks exactly what I needed.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk