I finished up the cylinder head this afternoon. I had long abandoned my plan to drill the remaining holes on the cylinder since they are all varieties of clearance anyway. Instead, I used a 1/16″ drill blank to center the piston rod hole previous drilling on the lathe under the mill spindle and worked from there. As long as I got the relative placement of the holes correct, all would be well. Or almost, anyway.
I used my milling pallet in the vise and clamped the head face down on a small square of hardboard. The hardboard is flat enough and allowed me to drill through holes without messing up the shiny surface of the pallet.
I had a bit of a bad moment when I went to test fit the head on the cylinder block and the screws would not fit in the alleged clearance holes. Only then did I remember that I needed bigger holes for the M2.5 screws I was using. Back under the mill and a bit of hole size increasing and it was done. Here is the head fastened to the top of the cylinder block.
Since I had some more time and had a head of steam up (hah), I took care of a couple of small tasks I had been putting off. I shortened the machine screw that holds the flywheel bearing to the main body so it no longer projects into the flywheel’s running space. I also cut and cleaned up a suitable length of 1/16″ drill rod for a shaft for the beam. After a bit of assembly, here is the current state of the engine. Flywheel shaft is still pending so the flywheel is just propped in place.