Thanks Bob I will try them, just for the record what is DOM and CDS tube..? Like to learn..For this you will need DOM or CDS tube, the ERW has all the weld snurgs hanging down inside. Depending on what you are trying to achieve you may well end up mixing metric and imperial to get that snug fit. Acton Bright are my go too on stuff like this, may be worth giving them a call http://www.actonbrightsteel.co.uk/.
Bob