TURNING 304L

[MoSHO93]

Ive been machining for about 23 yrs now and have had to machine 304 s.s many times. Never much liked it. I am currently turning some parts from 304L and not having much luck on tool life on my boring bar. Using the biggest insert drill we have (1 5/8), and having to bore 4.14 dia. thru with 2 steps of 5.544 dia. , and 5.92dia. Started at .125 depth of cut feed of .012 at 450 sfm. Oh using sandvik cnmg-432 insert 2025 grade. was getting 2 parts per corner. Went to .100 depth of cut at feed of .011 at 375 sfm and didnt get much better life. Anybody have any better luck with this. Thanks.BTW boring thru hole 2.2 deep.

[DennyAppsEng]

Heres a couple of my old tricks.

Change cut depths, .100 pass then .150 pass, then .075. This distributes the wear from that one spot that usually starts the rapid degrading of the insert.

In your case you may be able to face up. With the steps you have, and a good size BB that might work. Face up the two steps then use a standard Z axis bore for the rest.

The changing cut depths worked great on heat treated stainless...

Oh and buy a bigger drill

[scadvice]

Invite the local tool reps. to bring their tools and inserts for demo runs in cutting and boring these holes (in other words... on their dime). I've done it and it can be interesting and sometimes with good results. I would suggest having them show up on different days though.
Don't let them tell you its you coolant. (But, I would check it for its recommened concentration and if you have enough HP, push your feed rate a little more, 30 to 35% more at least, it seems a little low)
I like the idea of stagger depth boring, I never thought of that!

Steve