See Locogear Technical Bulletin #1 for wheel machining instructions.
Here is a comparison between the big Shay wheels and the Climax wheels. These are both 1-1/2" scale wheels:
A 1-1/4" x 16 tpi tap was acquired via eBay. These normally sell for $120 but one was found on eBay for $9.95. This will make all the internal wheel threads the same size. Axle threads will then be turned on the lathe to match.
Two adapters will be made for the lathe, one with a plain stub to fit the 1-1/16" axle hole and the other with a 1-1/4" x 16 threaded stub for the left hand wheels. Having 20 wheels of each type to machine it makes sense to build fixtures.
An interesting method of machining 1.5" scale wheels was proposed on the Chaski forum: click here.
Although I have a form tool for making the radius/flange of wheels, the thought of using that tool on 40 cast iron wheels made me wish I had another way to cut the radius. I also use some unknown steel billet for wheels that is the stringiest stuff to machine. I purchased some TNMG-666 carbide inserts from eBay. These differ from those in the Chaski discussion in that they have a built in chip breaker which should be helpful for machining the unknown steel blanks.
I will be making a tool holder for this carbide insert and will post a drawing and photos here.
Note in the photo above that the socket head cap screw is 5/16". This is a big insert.