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Jon Elson

wrote:
On Oct 31, 8:00 pm, Dom wrote:

... It isn't bolted down, but weighs 1200kg. (2640 lbs). I guess if it was bolted down, it might
eliminate some of the vibration.

Doesn't matter how much it weighs; the headstock needs to be bolted
down. Sounds like a nice lathe though, get 'er bolted down and you
should be able to get real nice finishes with some heavy cuts.
I have a 3500 Lb Sheldon 15" lathe, and it is performing
PERFECTLY, and on truly amazing cuts, too. It has an 8-point
foot system, but is not bolted down. it is sitting on a typical
home basement concrete floor slab. The manual recomends bolting
to the floor, but I don't want to drill big holes and set
anchors. If the machine's feet are not properly adjusted so
that the machine can rock, that could be a small part of the
problem. But, something else is wrong. I wish I could be there
to see what you are doing. It could be material, it could be a
problem with the machine, it could be technique (tool height,
tool geometry, speed, feed, tool holding, and on and on.)

I used to have a lot of trouble parting off on my Atlas lathes,
but the Sheldon does it like it was nothing. I did grind a
groove doen the center of the parting-off blade, parallel to the
length of the blade. (I only made the groove 1/8" long or
something, it will have to be extended as the blade is
resharpened.) The idea is to make the chip curl inwards a
little as the chip is formed, thereby making it narrower than
the cut in the stock. It works quite well, and prevents the
chips from binding in the cut.

I still try to keep the center of the compound pretty much under
the work to avoid a bending moment on the compound rest, even
though that is quite massive on the Sheldon.

The other thing I wonder about is the chuck. If the jaws are
not gripping well out at the tips, then you have a flexible bar
that you are trying to cut at a distance from where it is
actually being held by the chuck. Also, you can check with a
dial indicator to see if the chuck is not mounted securely.
What is the chuck mount? D1? L00? You say all this is new,
but something is wrong.

Jon