I am having problems w/ a new to me, very used Jacobs 900 series
collet chuck. First off, I have never used, nor have I ever seen any
one use, a collet chuck before. First problem, the collet holder
(nose pc or nut) threads on about 2/3 of the way and then frequently
binds. I can see that there is a groove in this part and a mating key
in the chuck. If I jiggle and unscrew the nut a bit it will go in
correctly about 1 time out of 4. Is there a special proceedure on
threading the collet holder to the chuck? Second problem is that I am
unable to secure the hand wheel via the locking ring. After
tightening the chuck / collet, and pushing the handwheel locking ring
against the handwheel, the locking ring does not hold the handwheel in
place when I start the lathe and engage the drive (note: I can feel a
very slight detent as I push the locking ring towards the handwheel).
The handwheel makes a pretty signifigant bang as it moves to the other
end of its travel. Same bang again when declutching. I would think
that this inertia and rapid stop of the handwheel will damage the
chuck in a short period of use - correct? What sort of a detent holds
the hand wheel locking ring in place and what sort of things to look
for in damage or misassembly to this lock ring asm?

In article ,
Aribert wrote:
I am having problems w/ a new to me, very used Jacobs 900 series
collet chuck. First off, I have never used, nor have I ever seen any

[ ... snipped because I don't know the answer to the above
part ...]

threading the collet holder to the chuck? Second problem is that I am
unable to secure the hand wheel via the locking ring. After
tightening the chuck / collet, and pushing the handwheel locking ring
against the handwheel, the locking ring does not hold the handwheel in
place when I start the lathe and engage the drive (note: I can feel a
very slight detent as I push the locking ring towards the handwheel).
The handwheel makes a pretty signifigant bang as it moves to the other
end of its travel. Same bang again when declutching. I would think
that this inertia and rapid stop of the handwheel will damage the
chuck in a short period of use - correct? What sort of a detent holds
the hand wheel locking ring in place and what sort of things to look
for in damage or misassembly to this lock ring asm?

I've not had a chance to work with such a chuck, but I have a
suggestion to something which you might be missing. If it has that much
free travel, it is probably there for a purpose. The purpose might be
to allow you to rotate the handwheel until the locking ring pins line up
with holes in the handwheel.

So -- try holding the locking ring pressed towards the
handwheel, while rotating the wheel. I suspect that you will find a
point at which the locking ring will suddenly move a bit more, and at
that point, there will be very little free play in the handwheel.

Sort of like engaging the locking pin when going from back gear
to direct drive on a belt-drive lathe. You have to rotate the bull gear
relative to the pulley to find one of the points at which it will
engage.

Good Luck,
DoN.
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Thanks for the reply.

The rotational freeplay in the hand wheel would appear to be for
loosening the collets (combination of freeplay & handwheel inertia) to
"hammer" the threaded joint loose.

To try to better clarify the issue in hopes that others will respond,
the locking ring when pushed up against the handweel does in fact
eliminate the freeplay. The problem is that the locking ring does not
stay locked - as soon as the lathe spindle begins to rotate, the
locking ring pops out of its (very weak) detents and the handwheel
once again has rotational freeplay.




(DoN. Nichols) wrote in message

I've not had a chance to work with such a chuck, but I have a
suggestion to something which you might be missing. If it has that much
free travel, it is probably there for a purpose. The purpose might be
to allow you to rotate the handwheel until the locking ring pins line up
with holes in the handwheel.

So -- try holding the locking ring pressed towards the
handwheel, while rotating the wheel. I suspect that you will find a
point at which the locking ring will suddenly move a bit more, and at
that point, there will be very little free play in the handwheel.

Sort of like engaging the locking pin when going from back gear
to direct drive on a belt-drive lathe. You have to rotate the bull gear
relative to the pulley to find one of the points at which it will
engage.

Good Luck,
DoN.