This project is a bust. I think it’s a combination of small amounts of bad implementation and large amounts of bad design. I did cut that 5mm keyway, but there were complications.
It turns out that the reamer I used for the sleeve wasn’t really a tight enough tolerance for the tool rod, and it wiggles. Not very much, but when you are trying to take off about .001" at a time, it really doesn’t take much.
There’s a bit of play in my compound. Not much, but trying to use this, every little bit matters. I should really make a block that can replace the compound for when I’m not using the compound, for additional stiffness.
Sometimes the QCTP shifted. I had put wrench flats on the custom top nut I made, so I locked the QCTP down harder using a wrench on the flats, which did improve things a little.
I was cutting a blind keyway, which means there is a hard stop at the end. This means that every cut ended with a shock to the handle. It broke at the attachment to the rod, at the weakest point, exactly where you would expect it to break if you look at the design. I didn’t expect these kinds of forces on it; I thought of .001" passes as something that should put light pressure on.
I locked that in place with shims and a clamp and used the carriage to finish making the cut with the spindle still locked (with aluminum cutoffs clamped to the outboard end of the spindle, since I don’t have a spindle break).
In the end, I discovered that I had locked the quick change tool post top nut down so hard that when I tried to unscrew it, the draw bar screwed out of the t-nut, and even clamping the draw bar in a vice, I can’t get the nut off the draw bar. So lots of failures to learn from. Fortunately I had an old QCTP, t-nut, and top nut that came with the lathe; I don’t like them but they are better than nothing.
So, I really think that before I cut more keyways, I need to go back to the drawing board.