Tricky bit

Decision time after much pondering how to attach the valve chest to the cylinder; well silver solder obviously but what shape should the mating pieces take?

In the event I couldn't come up with an accurate way to get a 2mm deep 11mm radius curve on the bottom of the chest so I decided to mill a flat on the cylinder rather than use curves. That does mean a change of plan for the steam passages though - rather than straight line drilling and milling they'll have to be drilled at an angle from the cylinder to the chest. Scary stuff!

Here's the state-of-play with a stub of steel in the valve 'ole and the piston poking out the back!