The lathing of the piston head came out great. Hopefully I can do as well milling the arm slots.
The slots themselves were kind of a pain, but went pretty smoothly. I’ve never had to mill anything using the dials on the handles before and I was worried about the accuracy. I made a test slot in a piece of scrap before this though and it came out perfectly, so I went into this with some confidence.
I cut the first 2 slots .008 undersized, thinking it would be best to take off the last hair with a file for a perfect fit. I tried a the fit afterwards and the arm didn’t fit by exactly that little bit, so I just said what the hell and milled the other 2 to the exact size. It turned out fine and they barely wiggle at all.
While the piece was still lined up and clamped in the vice, I drilled the holes as well. Even that took a while. Align, center drill, tool change, drill, tool change four times. Then I tapped the holes.
The fit came out nicely, but I had a hard time getting rid of all the burrs. I’ll have to find a new cleanup method. ..later.
I quickly cut out drilled and rounded 4 arms for the piston head. A this point, my plan was to carefully band-saw then file them down to the right length and curvature. They felt very rigid though, so I decided to take a change and cut them with the lathe.
This setup is kind of scary.
I was seriously gritting my teeth as I creeped the tool into the path of the spinning arms. It worked great though. It didn’t stall or explode anything at all. It cut off nice chips with a steady tak-tak-tak-tak-tak.
I turned the arms down until the outer diameter was 3.74 like the other pieces. The fit was a bit tight though, so I put it back in the lathe and took off another .02, now it has a little wiggle room, which is good.
And, the finished part. Not my prettiest, but very cool.