This morning started in on the center section of the steam chests. I went around the inside of the portion to be removed, and chain drilled a series of holes to remove the bulk of the material, leaving just the webs between the holes.
Then switched to a small end mill and plunge cut through each web till the center chunk could be removed.
After that it was just a matter of a few passes to take the opening out to size and smooth up the walls.
Next up was to drill the mounting holes, using the same pattern as used on the steam chest itself. These are all 2-56 clearance.
The last steps on the chests was to mill out the recesses in the sides to match the pattern in the original casting, which went thinner between the holes to reduce the amount of metal. First did the ends,
and then the sides. Due to the bosses sticking out, I used the other chest and one of the covers as spacers.
Then, a quick trip to the belt sander to round the outer corners, and the chests are done.
A quick test fit to see if I got the holes right - had to remove some burs and it all went into place.
Still need to make the studs to replace these screws, and a pile of small nuts to hold it all down. Same for the end caps on the cylinders.