Good evening all,
Can tell me, please, where I can get some thick walled free cutting mild steel tube that would make up into G3 wheels? Something like 2 1/8"-2 1/4" OD x 1 1/2" Bore. I tried to send a message to College Engineering but there may have been something wrong with their system, or mine, as the message wouldn't send. I have some solid bar but I'd be making a hell of a lot of swarf
Jon,
I've been down this road many times over the years.
One source of thick-walled tube is hydraulic pipe. The following web page gives the range of sizes that are available
Cold Drawn Seamless Hydraulic Tube (CFS NBK) | Hub Le Bas
There are probably two problems with this tube - the wall thickness isn't enough for a G3 tyre, and you might have to buy it in very long lengths.

But it is high quality drawn steel which should machine well.
Another option might be scaffolding tube - as shown on this web page.
Scaffolding Tube | Steel Scaffold Tubes
I suspect that the quality of steel may be a problem when it comes to machining and the wall thickness may be too thin. But you might be able to get your hands on a short bit if you chat up a scaffolder with a hacksaw in your hand.
Another possibility might be cast iron - specifically continuous cast tube - which would probably have a much thicker wall and should machine very well. But I can only find mention of it on producers' web pages.
So you might have to fall back on mild steel blanks parted off the end of solid bar. But you might be able to avoid a lot of swarf if you trepanned the centres out of the blanks . If you are fortunate, you might find that the trepanned blanks could be large enough to do smaller wheels - i.e. blanks for driving wheels produce trepanned blanks which will do tender or carrying wheels.
For my last wheel tyres, I got some very nice free cutting steel from the offcut shelf in a local engineering workshop and a very nice man with a very large lathe put a large drill through the centre which left most of the swarf on his lathe bed.
Jim.