Need Help!- Turning Long Aluminum Tube

[jasondaniell]

I am needing to turn a 44" long aluminum tube that is 2.5" in diameter. I need to be able to turn the entire length, so I'm planning on using a mandrel collet on the chuck end and a live center on the other. There is currently about .050" of runout in the part that I need to cut out. My lathe is a Haas TL-2 with a 2000 RPM spindle. I will be using Seco KX polished inserts. Any suggestions on whether or not my setup will work and suggestion on cutting parameters? Thanks in advance.

[Cruiser]

You didn't mention the wall thickness of the tube, It may want to sing like a tennor and chatter like a *****. We had to stuff them with rubber footballs to try to dampen the harmonics. Its going to be all about getting a ballance with the tubes harmonic tendencies.

[Geof]

You really need a traveling steady, that length and that diameter is going to be very springy. If you are going to try it without a steady filling it with sand or something, as suggested, may help. Use low rpm and reasonable feed, 500rpm and 0.01" per rev maybe.

Good luck.

[jasondaniell]

The wall thickness is .375. I may try filling it with something to help absorb vibration. I've never tried that before so do I have to be careful to get it completely full in order to prevent the filling from acting like a counterwieght?

[Geof]

I think you don't need to worry about any out of balance effect from your filling because it is a small radius turning slowly.

Before doing any cutting you can test whether your filling material works by tapping the tube with a hammer. If it still rings like a bell it will probably still chatter when cutting. Tap all the way along the tube at one inch intervals and you will probably find the ringing is different.

Lead shot would be the best for vibration dampening but a tube that size and that long filled with lead shot would be heavy.

[RICHARD ZASTROW]

Or maybe inject high density foam??????? Don't forget a method to remove it later.

This is just an idea. I've not used it, just heard about it.

Dick Z

[Cmailco]

No programmable steady rest?

[jasondaniell]

Unfortunately no programmable steady rest. I decided to cut it in two sections and so far it is working great. I chucked up on it with about 22" hanging out and ran turned that then flipped the part, chucked on what I just cut, indicated it in and ran the second half. No chatter, great finish. Thanks for all the suggestions though.