Ok last bit of work on the crank case:- cut the steam galleries, the drawing calls for the angle from edge to edge to be 60 deg, but for machining the critical feature is centre to centre of the cutter I'm using a 2mm slot drill so drew it up in cad and checked the cutter centre to centre angle 44 deg.
The mill was still set on the centre of the job, move the radius distance to where the ports will be, and rotated the RT 30 deg then off set 1mm to allow 1/2 cutter dia. lower the cutter 1 mm into work and rotate RT 44 deg. To make things simple I worked out the movement of the RT in advance and wrote out a crib sheet.
Like this

Ports cut

Last job tap all the holes:- I used my home made tapping stand, so that they were all tapped nice and square.


And there we are Crank case done.

Made a start on the cylinders I'm going to make these from ally with cast iron liners.
2" diameter length of ally being turned down.

I was hopping to get four cylinders out of this ally (one spare) but I forgot about the width of the parting tool so only got three, I'll have to be real carful
When making multiples its important to get certain key feature as near as posable all the same size, in this case its the width and the bore dia.
So by putting the job hard up against the back of the chuck and zeroing up the cross slide they were all faced off the same length.

Because of how I'm going to machine things down line I'm not particularly worried about getting the bore concentric with the OD. So sticking the blanks back in the chuck all the bores were centre drilled and drilled out with bigger and bigger drills.

They were all then rough out to within 1/2 mm of finish size with a boring bar.
Then finished off to size with the boring bar:- one after the other at the same setting, running the final cut through a couple of times to take the spring out of the bar.
For length they were all within 0.05mm and for dia 0.02 mm thats well fit for purpose.
Here they all are.

Next job the cast iron sleeves.
Have fun
Stew