On Tue, 12 Jan 2016 19:27:41 -0600, amdx wrote:

On 1/12/2016 4:10 PM, Ed Huntress wrote:
On Tue, 12 Jan 2016 15:59:08 -0600, amdx wrote:


I have one of the Harbor Freight 7 x 10 lathes.
I have a bicycle seat post that I want to reduce the diameter by 0.025".
The spindle head is to small to accept the post, the bed is to short to
use the tail stock.
Any clever ideas how I could use this lathe to do the job. The post is
aluminum.
I took it to a machine shop, he laughed and said, "I've already spent
more time on this than the part is worth."

Mikek

You need a steady rest (Google "lathe steady rest"). For a one-shot
that doesn't sound at all critical, cutting aluminum, you can make one
out of plywood that will do the job.

Yes, as I wrote the question, I thought, I could make a holder for the
live center out of wood and bolt or clamp it to the end of the bed.
I did see a steady rest someone built for their mini lathe, it was
very nice but quite a project.

Well, you may want to rig a center, or just a steady rest. If you
have room for a center, that would allow you to turn the whole length
at once.


You may find a plan or idea for one online, or maybe someone here can
tell you how to jury-rig one.

However, if the bed is too short to use the tailstock, it raises the
question of how long this thing is and how much of it you want to turn
down. A long, thin aluminum tube is going to present a deflection
problem, in which case you may have to rig a follow rest in addition
to the steady rest. You can look that one up, too.

It's about 12", 11" of it I need to reduce. I'm not to worried about
deflection, it just needs to slide in my bike frame tube, nothing
precision about it.
It's a seat post with a spring in it, I want a little more protection
for my compromised spine.

Thanks, Mikek

The issue with deflection in this case is not accuracy so much as the
ability of the tool to cut, if the work springs away. Or, much worse,
especially with alumimum, is a positive-rake tool digging in, pulling
the work toward the tool, and wrecking the work.

Cutting aluminum is pretty easy, and skating of the tool is not
generally a problem, but use a sharp tool and try zero rake to avoid
digging in.

--
Ed Huntress