I have just acquired, at great expense, a piece of steel tube 8" I.D. and 3/4ins. wall thickness. I am about to start machining it to produce six steel tyres which I intend to shrink onto three pairs of existing, cast iron wheel sets (after machining off the current treads). The plan is to make the tyres with one thou per inch of interference, expand them with heat then shrink them onto the wheels. Before I pluck up courage to do this job does anyone have any advice to offer? Barrie MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.