A 9 inch such as a Boxford is a pretty good size for most model engineering though a smaller 7 inch is adequate.. You should not be looking to swing the rear wheels or even the flywheel necessarily as there are other ways of turning the big bits. Depending on whether you have a milling machine look at how you will turn the underside of the cylinder block to the diameter of the boiler.

Edited By Bazyle on 10/11/2013 23:08:26

This is a question I've been trying to answer for a while. As a beginner I thought my mini-lathe (C3) would do me while I got a few projects under my belt. In theory it is a 7" swing but I've learned that there is more to it than that. I struggled to machine the rim of the 3" flywheel for the S50 I'm making because the cross slide would only just retract far enough. I suppose you could use a LH tool in the back of the tool post but I'm not sure how successful it would be. If I decide to buy something more capable in the future I'd like to be more aware of what its limits were.

Any comments from the more experienced members would be much appreciated.

Gary

Rather than get a big machine just to make one or two flywheels in your life check out evening classes or clubs that have machines you could use. There are also possibilities with rotary tables and a milling machine. Many of the larger items are available part machined too as the suppliers don't want to lose a potential customer so even if they don't list it always ask. If they don't come up with something you have to ask how good they will be on other support issues.

One of the things you might find more difficult is the cylinder block. You will either need to swing it all on a faceplate or be able to mount it on the saddle to use a boring bar between centres. Next you need to be able to swing a boring tool at the boiler diameter over the saddle to machine the curved mounting face. that could be the constraint. Or you do it on a mill. If you don't have a mill nowadays it is probably better to put spare cash towards a mill rather than a bigger lathe.

BTW Jason is the forum No1 TE man.

> I suppose you could use a LH tool in the back of the tool post but I'm not sure how successful it would be.

Works every time, as Jason's picture ably demonstrates. Just keep the speed modest and use the 'low' gear. Watch the motor doesn't get to hot, take a half hour break if it does.

Neil

For anyone else thinking of turning a flywheel on a mil like that make sure you have replacement final drive gear available for it. They may be designed to drive a six inch slab cutter but that's not the same as the energy in a big flywheel. You can do it but better to freewheel the drive and use a belt round the rim.