On Sat, 10 Dec 2011 13:15:25 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I must bore and hone a 6061 6.125" cylinder 15" long on my 14x40 lathe.

It must be smooth and round, but the actual i.d. is not important (except
to document on the drawings).

I have no experience boring long, large tubes, and figure tool flex is
going to be the primary problem.

Any hints on what size boring bar and cuts I'm going to have to take to
make this work? (none of the local machine shops, including a marine
diesel shop, will take it on).

LLoyd
Greetings Lloyd,
You have gotten many suggestions already. Making a bar from pipe will
help with the rigidity issue. Since you are only doing one and are
going to hone it I would suggest grinding the tool tip with a very
small radius. .005" would do. Run the lathe as slow as possible, use
cutting oil, and try dampening the vibrations with your fingers.
Sometimes when I do jobs like this I oil the outside of the tube and
press my fingers against the rotating workpiece to dampen vibrations.
It does wear out your fingers so holding a small piece of leather or
wearing a leather glove helps. I know this can be dangerous. I
probably wouldn't let someone do the above in my shop. But I do do it.
The finish will suck with the small radius tipped bar but you are
honing it anyway. If you are considering sending it out I can
recommend a very good shop in the Seattle area. They do a great job at
a reasonable price.
Eric