The Potty Mill Engine sounds ideal for what you want. It is a simple horizontal mill engine with simple bobbin type slide valve gear all made from bar stock and cheap metric fasteners. Plans by Stewart Hart are available free on the net, somewhere but I forget where, and it was featured in MEW mag as a Dads and Lads project and plenty of build threads and videos around. If you google Potty Mill Engine you will find it all. Maybe in the Plans section of the modelenginemaker.com forum site.
I made my flywheel out of an old steam valve handwheel, the rest was all bar stock.Pictured here part completed without the eccentric and linkage. I built it as a test project for my newly restored Myford lathe, just to give it a workout. No milling machine required. Just the lathe and drill press, but it could be all done in the lathe easily enough.
Edited By Hopper on 15/02/2023 08:13:08