I've posted these pics before, but like all of my past posts with pics, they disappeared. I have been machining these forgings for a few years. They suck. Really suck. But over time you figure out better and faster ways of doing things. Faster and cheaper= less sucking.
They are just a mild steel forging. Dead soft and kind of gummy. Nothing special. I wish they were a medium carbon steel because they would machine nicer. Their odd shape makes them difficult to hold onto. I have to stand them on edge and grip on a narrow tang to qualify the major diameter. Took a while and some trial and error to get it down pat. In the pic you can see the little "stops" sticking up on the left side of the vise jaws. I use a 1-2-3 block standing the 3" way to square the part and locate it left to right.
Now to machine it is another challenge. The part needs to be round. No way to chuck it in the lathe and no way to interpolate it round standing on edge on the pic. (I did try one time. But because of the flimsy tang, it squealed like a stuck pig).
So onto some custom tooling. I made a hollow mill. The first one was just a hunk of round turned down to be clamped in a end mill holder and bored and slotted to accept 3/8 shank brazed carbide turning bits. It worked OK. But it was hard to set the tools, they liked to chip the carbide, and it wasn't all that rigid. I switched to some small inserted tool holders. It solved setting the tools to the correct position, but they were a weak insert, and the lack of rigidity caused the inserts to fail way too often.
I needed something else. After a lil head scratching and some doodles on paper, I came up with a perfect design. Rigid, repeatable, and reliable. And it looks pretty darn cool too. Grabbed a chunk of D2 I had lying around and started whittlin. I used two left hand lathe toolholders with CNMG style inserts. Mounted it to a CAT40 facemill holder. Nice and rigid. I did have play with it a little to get them set to cut the correct diameter. The tolerance on the part is quite wide open (+/-.005). I had to take few test cuts and then shim the toolholders accordingly. After they were shimmed, with any insert change, they still cut perfectly to size. One tool is set lower and slightly larger than the other. Basically one roughs and the other finishes. With the tool being some much more rigid, the chatter was eliminated and the inserts last forever.
