johnsmachines

The 2mm end mills arrived, so I have started machining the steam passages.

The steam inlets are 2mm wide and between 12.7mm and 31.75mm long, and up to 12mm deep.  I had planned to angle the passages, rather than placing them at 90 degree angles, but realised that angled passages would impinge on bolt holes, so I have reverted to the original plans.

First I marked out the steam ports.

The cylinder blocks, painted with marking out paint, ready for marking.

Milling the slots.
Here I am using a 2mm end mill to cut the inlet ports. . Feed 60mm/min, 6000rpm, 0.25mm slices.   HSS cutters were not up to the job, becoming blunted quickly and then breaking.  The carbide cutters performed well, at 6000 rpm.  Each slot took about 30 minutes to cut.

The completed low pressure cylinder steam ports. 12mm deep, 31.75mm long.

Next I will need to drill holes 21mm deep, 2mm diameter, to meet up with these ports.  The holes will be placed along an arc, just outside the cylinder walls.  Pretty tricky.  But so far, so good.