Thanks for you kind support chaps
I had to change the layout of the holes in the steam chest, when I came to try the chest on the cylinder to see how thing looked I realized that changing the air feed hole position meant that I would break through into them with the steam chest fixing holes, not as though it would have been a disaster as the studs will be sealed in and the chest will be sealed on the cylinder but I thought it best to avoid it.
So with the new layout marked on the chest first drill them 3mm

When I milled the steam ports and machined the chest I marked the center line with a tiny dimple from the centre drill, this is so I will have a mark to line things up. So with two way sticky type on the chest stick it to the cylinder centrally and square using the marks and the back edge of the chest lined up on the back edge of the cylinder, then with a little transfer punch made from a bit of 3mm silver steel (drill rod) mark the position of the holes in the cylinder.

Set the cylnder level using the digi level, a real handy bit of kit , carefully line up on the marks with a centre drill and then drill M3 tapping.


Then on the tapping stand and the cylinder jacked level using a sine bar tap the holes nice and square.

Now for the cover a bit of 2mm brass plate was rough cut out and the chest placed on top and a line scribed round it.
Mill to the line, the parallels are to reduce the angle of dangle and give it a bit of extra support.

Then clamp the chest to it and drill through when you've done the first hole put a clamp bolt through it do the second and put another clamp bolt through it as well, remove the clamp and drill the rest of the holes, I used a number 31 drill to give a little wiggle room.


The hole in the middle will take the air intake flange the top of this flange will be leveled off so the hole in the cover needs to go in at an angle, so with the cover bolted to the chest and set up at 15 deg, first a big centre drill followed by a slot drill this angle the hole nicely.

This is the cylinder assembly so far

Stew