What do you call a "slight curve" ? Allowable curve is 1.5-2.0mm over 1000mm.

Problem is if someone picks up a 3m length the wrong way it will bend under its own weight and won't spring back.

It is likely that a 3m length would be picked up in the middle, so the overhang becomes 1.5m, or about 59". The system is symmetric, so we can ignore one side. We then have a beam fixed at one end with a uniformly distributed load, ie, the weight of the material. A 59" length of 3/8" by 1/8" flat has a volume of 2.765 in³. Low carbon steel has a density of 0.283lb/in³, so the beam weighs 0.78267lb, uniformly distributed along the length. Maximum stress is at the support, and is given by Wl/2Z where Z is the section modulus. Assuming that the 3/8" dimension is horizontal this works out as 23642lb/in². The yield strength for low carbon steel (1018) is about 53000lb/in².

Andrew

Now now boys !!

Not forgetting must be thin edge top and bottom.!

It is handy though, as it applies to anything you want to lift/support with as little chance of distortion as possible – using a forklift or a fingers! Presumably it's also the best spacing for the legs of a lathe bed (ignoring the weight of the headstock) and I wonder if it determines the spacing of the uprights on the old Severn Bridge?

> Though would not want to try lifting a heavy bar like that

I initially read that as meaning you wouldn't want to lift the 3m of 1/8×3/8" bar… rather than 'lift a heavy bar in that way'.

Neil