In article ,
Fred Splittgerber wrote:
Hi all,
I am aware of the fact that parting is (usually/always?) not recommended if
the workpiece is held between centers.

Always. Think of what happens when it gets down to the point
where the remaining section is easy to bend. It will bend (away from
the parting tool, or up), rotate up, and slam down on the parting tool,
likely leading to something breaking, and at least to marring of the
workpiece.

What about parting off with the workpiece mounted between a regular 3-jaw
chuck and a live center? (1/4 hp lathe, Workpiece: brass, 5/8'' diameter).

I do it when working with fairly large and long workpieces, with
one caveat. Before I get to the point where it will *really* part off,
I loosen the center a bit, so it won't pinch, but the center will still
catch the free end. (Usually, the parted end winds up resting against
the side of the parting tool.)

The center serves in the early stages to keep chatter under
control, but once you are down to perhaps 1/2" or less left (of a 3"
workpiece), it serves little purpose, and could generate problems when
the part is (nearly) completed, binding the parting tool between the
workpiece in the chuck and the part just parted off.

Always think about what could happen when you are trying
something, and take steps to prevent the bad ones. (E.g. removing the
center's pressure before you get too deep, but after the support is no
longer needed.)

Enjoy,
DoN.
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