The next phase in construction is the cylinders and heads. The heads will be made from aluminum with pressed in steel seats and bronze valve guides. I think when I made the first engine I used continuous cast iron for the cylinders. I don't remember. Not having any material the right diameter I opted to use 1144 stress proof steel. The fins on the heads and cylinder barrels are .035 thick with .040 spaces between. On the cylinders the fins are .200 deep. The first thing was to make a tool. I took a 1/16 thick high speed cut-off blade and ground one end to .04 while trying to maintain draft on the side of the tool.

Yes there will be a lock nut. Imperial 1-72 thread is .073 diameter (1.85 mm)  In the Metric world  there is a 1.8 x .35 size.

 

The top of the door does seem to line up with the notch - but the bottom looks a tiny bit above the #37 hole, so you could make it a touch less than 3 9/16" perhaps.

Wilf

This is true, Wilf, and I considered that.
But the bottom of the doors line up exactly with the 3/8" mark for the center of the boiler cut out.  What's weird, is that his 3/8" for the boiler center and the 3/8" for the #37 screw holes don't line up.  So I chalked it up to him doing all his drawings by hand.  Or maybe he was showing that the holes are independent of the boiler center mark and the doors, even though they are shown with the same dimension.  I don't know.  Or maybe he felt that the counter sunk screw holes might interfere with the edge of the door, so he showed them a titch lower to keep them from interfering?  But if that's the case, why didn't he make them a 5/16" or 11/32" or something?  I likely will never know!

Kim

Looks like another good design Jason! That will make for a pretty nice model!

 John