I was reading a very interesting IRS thread that extended to seven pages and counting.

http://locostbuilders.co.uk/viewthread.php?tid=6802

Where has the rest gone?

And while I am here, I can get 25x25x1.5 and 1"x1"x1/16" box section MS. Which is the suitablest?

Well ones metric and the other is imperial. Both are suitable, it makes no difference. Just make sure you make all your length measurements in either metric or imperial, or you will get compound errors and end up with gaps.

David

Due to my job (AutoCAD Draughtsman), I find the 0.4mm difference very important. It is a cross I have to bear, and is considered quite sad in certain circles (namely any circles with normal people in). If I choose metric, I will model the chassis in CAD - just to find all the missing 0.4's from Jim's plans. Very sad I know, you should see me laying a patio....

Yes, and when i modelled it in CAD i found those errors too. I belive that as long as you stick to one system with the tube from the same system the measurements should be right....

The 0.4mm does add up as you say, and this is what i was trying to get at in my first post....

If you are worried about 0.4mm, then for goodness' sake don't measure the diagonals as the book suggests!!!!!!

If you can get them to 0.4mm accuracy then I'll eat my hat right now!!!

Luckily my tape measure doesn't have parts of millimetres on it. I don't think you should get bogged down worrying about deadly accuracy when you can adjust your bracket fixing points to even stuff out a bit. I found some 25x25x1.5 stuff and noticed the corners were a lot squarer than the imperial tube I used. It doesn't look as user friendly.

You are dead right - I should not get bogged down with such trivia.

Unfortunately, I am now concerned about the radius on the metric steel. I really should get out more!