On Thu, 29 Sep 2011 18:27:20 +0100 John Williamson wrote :
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.

The figure I have for S235 mild steel is a yield strength of 460N/mm2.
6mm rod has an area of 28.3mm2 x 460/1000 = 13kN, or 1.33 tonnes.

--
Tony Bryer, Greentram: 'Software to build on',
Melbourne, Australia www.greentram.com