On 14 Mar, 22:29, "Carl Boyd" wrote:
"Amr" wrote in message

...



Hello all,

I have a SIEG C1 Micro Lathe (http://www.axminster.co.uk/product-
Axminster-SIEG-Axminster-SIEG-C1-Micro-Lathe-33289.htm), which I
bought from Axminster a year ago, although the lathe itself doesn't
see heavy use (perhaps, say, once a month?).

Recently, I've discovered 2 problems while turning. The first is that
my work is tapering, with the diameter being larger near the chuck.
I've run a clock along a test piece and have found that there is a
0.15mm deflection across a 55mm length, giving a 0.3mm change in
diameter. The second is that if I place the clock on the work near the
chuck and rotate the chuck, I find I'm getting deflections between
0.03 and 0.15mm, but they don't seem regular - the needle looks like
it's deflecting randomly.

To take these measurements, I put a 10mm diameter, 100mm long mild
steel rod in a 4-jaw chuck with about 60mm protruding and got it
running roughly true. Then I started taking light cuts across the
protruding length (touching on and feeding across). A clock was then
used to take the readings.

The lathe itself is just sat on a stand (seen here
http://www.axminster.co.uk/recno/2/p...EG-Stand-for-M...)
but is not fixed to it at all.

I can't say for sure when these problems started to happen, because
it's only recently that I've started to actively watch out for them. I
have a hunch that the tapering started quite recently when I removed
the lathe's 3-jaw chuck to try out the 4-jaw chuck that I had just
bought. But as I said, I really couldn't say for sure.

As a novice, I'm not sure whether these defects are ones which I can
fix myself or if they're serious problems with the lathe. I was
wondering if I could get some advice regarding these issues?

Thanks

--Amr

All your symptoms could be caused by the 4 jaw chuck being loose on the
spindle, or the jaws being loose in the body of the chuck. Put clock (I
assume that this is a dial indicator) on the chuck and see how much you can
move it left/right and up/down, repeat with your test bar. 10 mm is kind of
small, does your 4 jaw hold it tighly?

Carl Boyd

Hi Carl,

Thanks for your reply. I've done the suggested measurements and have
found that the chuck doesn't move left/right at all, but moves up/down
by about 0.01mm. Same with the test bar at the end, except it's up/
down movement is 0.02-0.03mm. The chuck does seem to be holding the
work tightly - doesn't seem to be any play. How does that sound?

--Amr