Thanks for all the replies!

William, I like your idea best. Not so much because of the collapse problem, I
was not going to cut all the way through the tube but save the final cut for a
hand saw - like any parting off. Any "fringe" will be sanded off.

But by using your plan I can make use of that piece of closet rod I have kicking
around (it doesn't even need to be a full 36" long.) I'll be able to hold it in
place with my large Oneway live center in the tailstock. I'll true up the rod,
measure the diameter and cut holes in the spacer discs to fit over the rod.
After they are glued in place I can true up and adjusted the discs' diameter to
the ID of the HDPE. The tube should fit snuggly over the mandrel and if it slips
slightly while turning I can put a wedge between the disc and the tube. That way
I don't have the problem of a wobbly tail piece and I can also cut all the way
through!

In case anyone is interested in why I want to turn this stuff: I'm also a
pyrotechnician and I'm building a ball mill. The short (~11.5") segments of the
HDPE tube will have lids fitted to the ends and will function as milling bottles
with 3/4" lead plugs inside grinding chemicals for my pyro work. Only one tube
will be cut into 3 "bottles", 3 other tubes will have only one segment removed.
That will give me 3 bottle sets (use 2 at a time.) That way each set can be
devoted to tumbling only certain chemicals and avoid cross contamination. The 3
tubes that will be left at 24" long will be used to fire mines instead of
regular aerial shells.

All these will require more lathe work since the end caps for the bottles will
need to be a snug fit and the mine tubes will need wood end plugs. There is a
lot of things you can do with a lathe besides bowls!

Thanks again

Terry,

william_b_noble wrote:

having attempted this a few times, let me humbly suggest that you make a
mandril that fits snugly inside the tube rather than the cones - I can think
of several ways to do this, but start with some MDF (or other scrap) disks -
3 or 4 of them, space out with scrap lumber, drill through for a rod (use
water pipe maybe), then slide the tube over it and put the whole mess on the
late - that way when you cut the tube it won't collapse on you
"Terry Clark" wrote in message
...
I need to cut up a 6" HDPE tube with square ends. So I'm thinking of
mounting it on my lathe with cones to center the tube and keep the cuts
square.

The problem is I can see how to turn a cone (or at least truncated cones
for this large of piece) that will mount to the headstock but not sure
how to keep a cone straight when held in place on the tailstock. Yes I
know the pressure will hold it in place but this tube is 36" long and I
can see problems trying to keep the whole mess in alingment while trying
to tighten the tailstock.

I'm thinking of drilling several inches into "face" of the cone with the
Jacobs chuck while the cone is still unfinished and still mounted to the
headstock. Then when I mount that cone on the tailstock run a steel rod
through the tailstock in hopes that would help stabilize the alignment.
The rod OD would have to be the same as the tailstock tunnel's ID to
reduce the slop.

Anybody had experience using large cones to center tubes?