The crankshaft for the poppet valve single cylinder engine has been machined from mild steel and includes timing gear machined directly on the shaft.
This started with a piece of hexagonal mild steel, why hexagonal? Well, I bought a job lot of mild steel on ebay and as it machines so well this is what I selected for this part.
The webs of the crank are just wide enough to still fit a 3-jaw chuck. Note the use of the rotating centre to align this perfectly.
I started the machining in the Warco WM240B lathe.
Re-aligning the crank in the lathe allowed me to later machine the bearing surfaces to size.
As the crankshaft and timing gear were in one part I had to make the bearing large enough for the gear to fit through. This meant I needed a ball bearing with a large ID.
I have to say, the finish of the crankshaft is superb. A clean cut, burrs removed from the edges and a quality thread cut into the end.
The crankshaft for the poppet valve single shown from different angles. Note though that the big end pin is missing.