"DoN. Nichols" wrote in message
...
In article ,
Tom the Tinkerer wrote:
I believe it has a tapered spindle (havent been able to remove the
backplate
to see) the three bolts on mine are allen bolts, I've tried with both the
chuck still attached and removed, and soaked the spindle in wd-40 / RP7
to
try and loosen the connection.. the 4 jaw chuck does have its own
backing
plate, and if real worst comes to worst, i can probably re- machine the
backing plate to accept a new chuck, but i do like using the original
parts
and this wouldnt really help in the long run, as i'd eventually run out
of
backing plate

The "Locking bolt" is on a collar that fits around either the threaded
section or tapered section of the spindle (again not sure) , I believe
this
had been added after market to stop the chuck spinning off when cutting
in
reverse

Tapered and threaded don't normally appear on the same lathe --
with one exception which I will mention below. If it is threaded, there
should be a register following the threaded section. (That is -- either
the same diameter as the threads, or larger, but cylindrical, with a
step increase in diameter afterwards, which serves to locate the chuck.

If you have a locking bolt, it is most likely to be decreasing
the diameter of the register part of the backing plate (via a split) to
clamp onto the register of the spindle -- for the very purpose which you
suggested. You may simply have a case of some rust having formed where
the two meet, from water wicking down in the slot which the locking bolt
clamps. You might try loosening the clamping bolt, and then driving a
thin screwdriver blade into the slot to expand it a bit, and see whether
that allows things to unscrew. Add some penetrating oil and perhaps
some controlled heat to encourage the penetration. (More on this
subject after the exception paragraph below.)

* The one exception to the "threads don't mix with tapers" rule
which I suggested above is the L-00 (and other sizes, all
starting with 'L'). This has a long taper, with a key mounted
to the spindle nose, and a keyway in the female taper in the
chuck backplate or the chuck if it comes without a backplate.
The female taper on the chuck has an external threaded section,
which is engaged by a loose threaded ring on the spindle which
draws the chuck firmly onto the taper. To the best of my
knowledge, Emco did not use the L-00 on any of their machines,
though it is possible that E*n*co did -- totally different
machines.

Threaded spindles have problems which require proper care to
avoid.

1) The threads on both the spindle and the chuck *must* be clean
or you risk getting the chuck stuck in place. You should make a
spring loaded tool to clean chips out of the threads, and use
it before mounting the chuck each time. (The register should
also be clean.)

2) Another problem can come from either putting the chuck on
loosely and starting a cut, or from noticing that the chuck is
starting to unscrew from the spindle and switching it into
forward to catch up with the threads. Either case causes the
chuck to seat rather too vigorously, and risks having it on
tight enough so removing it will be difficult at best.

It was a combination of the two above which led me to replacing
my spindle (2-1/4x8 threaded) with an L-00 spindle when the opportunity
arose. I have not regretted this conversion. (And I *did* have to
fight a too-tight chuck a few times.

Note that there is one sure-fire way to deal with the problem,
especially since your chuck can be removed from the backing plate.
Remove it, procure a replacement backing plate, and machine the old one
off of the spindle. Eventually, you will get down to the spiral of
metal which made the threads of the chuck backing plate, which should be
easy to unwind or unscrew from the spindle. Be careful with the
register area. This is less likely to damage the lathe itself than some
of the more vigorous means of freeing a stuck chuck.

Since you have another chuck which fits the machine, examine it
closely, to see just how it works.

Once everyone knows what kind of spindle you have, you should
get lots of suggestions on how to remove the stuck backplate. Since
Emco has used several styles of chuck attachment over the years (mine,
for my Compact-5, bolts the chuck to the spindle nose by Allen-head
bolts passing through the chuck body between the jaws), and since some
at last seem to be confusing Emco with Enco (the latter, in recent
years, selling imported Asian lathes -- mostly Chinese and Taiwanese).

Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---


You would be right
at the headstock end of the nose there is an unthreaded portion, which is
where the clamp fits, i will attempt the levering of the collar this
weekend, although finding internal jaws would solve my problem for a while
too.. I'll have to try and source a new backplate as well. although i feel a
little anxious at cutting the existing backplate off
Thanks so far G

Tom the Tinkerer
Horologist in training
NSW Australia