Pinch and balanced turning in 15-5

[nickbe10]

Anyone had any experience doing pinch and /or balanced turning in 15-5?

We need to make a large "dogbone" out of 3.75" diameter 56" long 15-5.

The diameter in the center is 1.2" and the wall in this region is 0.085 (did I mention it is gundrilled?).

We are looking at expanding mandrels and an LU-35 to get the job done. Anyone had experience doing this sort of thing in 15-5? Anything in particular we need to be careful about, particularly with this material? Normally in milling work (where 98% of my experience lies) work I find the material to be free cutting and stable, so its really anything different in turning with these techniques I would prefer not to get blind sided by.... trying to gather as much info and research as possible before starting...

Any / all advice much appreciated.....

[workmantm]

We had a similar shaped but, but much smaller is 15-5 H1025. Gcode programmed it and we ended up running a SNMG 15deg lead holder for some pretty solid performance and tool life. I’d have to dig out my programs to see what S&F we ran, but we had excellent chip breaking with this approach. We used a false center and tooling spud because we had to mill flats in it after turning plus some other mill work. Ended up sawing off most of the spud and turning the end radius to a near match.  

 

Did pinch turning on a different part and it wasn’t an issue normally. Only issue I saw was poor forging a that required more material on an interrupted cut to be removed and the tools not liking that extra .07 I had to move Z to get a good clean up. 

[taperlength]

Used to turn 15-5 on an Okuma years ago.   Nowhere near that long though.  Nice feature on the Okuma is the LAP cycle can be modified with decreased depth of cut and/or feedrate depending on the diameter.  So it can start roughing with heavy cuts and then at  specified diameters, reduce the DOC and/or feedrate.  As I recall it is a G84 line after the G85 line and before the G81 line.