Thanks for the tip sparky, lets hope I get this right.
These are not the first parts for my Stirling powered fan as I managed to leave the others at work, but hopefully these will give you a wee taster.
This is the cylinder for the power piston being turned down, the instructions said it should be bronze. But alas I had none and managed to find a bit of brass that had been used as a (rather large) punch. I also didnt have a piece big enough to make the cylinder and its base from one piece so I am planning on making it in two parts and soldering them together, can anyone see a problem with this?

The next part was to bore it out to 0.7500 and pollish the tooling marks to ensure a nice snug fit for the piston. I was a bit nervous doing this as I had only ever done it once before and that was just two days ago!

Next up is the piston and cylinder together. I am really pleased to say that they fit perfectly

I taped the hole in the piston and one end of the cylinder and tried to push one inside the other, on letting go the piston sprung back just as it should. With the tape removed the piston slides right on through. Just a wee bit of pollishing and they are done.

As mentioned above I didn't have a big enough piece of brass to make the piston and its base in one go, but I did find a nice piece of copper from a bus bar, albeit a little bent! So in the mill it went.

Yes the mill and vice are straight, but the copper bus bar link isn't.......................yet.

Now it is cut to 1/4" thick and given a bit of a pollish before going back in to be cut down to size and have its perimeter squared off.

once it is down to size I need to drill a hole at each end for securing it to the engine base, find a way of boring a large hole in the centre and then brazing it on to the cylinder part. What I am thinking of doing is securing it to the milling table, putting the cylinder in the hole and using a centre in the mill to keep it square and true. Then get the gas torch out and braze or silver solder the two parts together.
It's desperately slow progress as I am learning as I machine, but hey, Rome wasn't built in a day and I would rather take it slow and easy to ensure I get things right first time.
Cheers
daz