We’ve had a job in our shop for the last twenty years that requires turning 4130 tubes. (ID and OD) Our surface finishes and tolerances are acceptable, however we’re now adding robotic loading/unloading to a few of our machines, and this job is an excellent candidate for it, provided we can solve our chip (or lack thereof) problem.

We get long, stringy chips that are turning into a rats nest and require manually removing from tools or the workpiece at the end of every cycle. It renders the chip conveyors useless, and we end up having to routinely remove a giant razor sharp tumbleweed from the machine door. I’ve played with the speeds and feeds and achieved tight coils, but can’t seem to get them to just break into a damn chip.

Our setup is as follows;
Haas SL-20

For ID roughing, we have a .750 shank boring bar with a Korloy DCMT32.52-MP (32 nose radius) (NC3225 Grade). Depth of cut is .050”, 480 SFM, Feed Rate is 0.018”, Cut is continuous.

For ID Finishing we have a .625 shank boring bar with a Korloy CCMT32.51-MP (15 nose radius) (NC3225 Grade). Depth of cut is .020”, 550 SFM, Feed Rate is .006”, cut is continuous.

For OD Roughing we’re using a Korloy DNMG432-VM (32 Nose Radius) (NC3225 Grade). Depth of cut is .050”, 800 SFM (Have tried as low as 400, and as much as 1000), Feed rate is .013”, cut is continuous.

For OD Finishing we’re using a Korloy VNMG331-VL (15 Nose Radius) (NC3215 Grade). Depth of cut is .020”, 1000 SFM (Have tried from 600-1300 as suggested by Korloy) Feed rate is currently .005”, (anything over .006” and the finish turns into a record player) cut is continuous.

For the workpiece, raw stock is a 3” long, 1.875” Diameter, and .200 wall thickness. The material is normalized, and has not undergone any hardening/heat treating process.

I’m not married to any specific brand tooling or geometry of insert. I just need to figure out how to make this damn thing make chips so we can run it unmanned. I’m open to any/all guidance, I’ve been banging my head against the wall on this for the last three days, and it’s driving me nuts.

Our Korloy representative has sent us a DCMT with a different chip breaker arrangement, with a NC 3215 grade which he thinks will do a little better, however given the fact that our inserts have all different chip breaker arrangements (MP, VL, VM) I’m thinking that I’m overlooking something here. To make things worse, I am by no means a machinist, a week ago I had no idea what any of the above meant, and I didn’t even know how to modify a program on the control. I’m just the one getting thrown at the challenge as everyone else in the shop is busy with the more immediate money making projects. So, if anyone out there can lend a hand, I’d be very grateful.