On 2018-10-20, Jim Wilkins wrote:
"DoN. Nichols" wrote in message
...
...
Another approach is to take an appropriate length of 2x4, put it
between a jaw on the back side of the spindle and the lathe bed, and
engage the motor in reverse with the back-gear engaged to unscrew
the
chuck.

Personally I wouldn't subject a leather belt drive to that much shock.
I keep mine loose enough to slip before something else breaks.

Well ... my lathe has three parallel V-belts from idler shaft to
spindle, and one bigger V-belt from motor to idler.

And I wasn't talking about shock. Rotate the chuck so a jaw is
holding the 2x4 between it and the back of the bed.

With flat leather belts, do the same, but let it slip a bit as
you start the motor, and then adjust the slip out.

The only task that has made a chuck difficult to unscrew is turning a
square blank round. If I bandsaw the blank octagonal there's less
temptation to speed up the job with a heavy interrupted cut.

Granted, it is an extreme condition.

Chips in the spindle nose threads, or those in the chuck can
cause the locked chuck. The _How to Use A Lathe_ book (either the
SouthBend or the Atlas one, I forget which, has a drawing of a
spring-loaded bit of wire with chisel ends to clean chips out of the
internal threads in the chuck or the chuck backplate. A wire brush on
the spindle nose helps there, too.

Also -- a loose chuck on the spindle when you turn on the motor
can lock itself in place when the spindle runs up into the chuck
backplate.

I've never had to turn off the backplate on a locked spindle,
though that is something to keep in reserve just in case.

But I do very much prefer the L-00 spindle nose and backplate.

Enjoy,
DoN.

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