According to :
First off -- I got two e-mails from you today -- with the old
return address which your usenet articles show. I am not going to
bother typing answers to them, only to have the answers sit for a week
and then pop back up as undeliverable.

*If* you posted as well as e-mailed, I'll try to answer here in
the newsgroup. If you didn't -- then take this as a reason to not send
me e-mail copies of usenet postings, or e-mail with bogus return
addresses.

I wouldn't intentionally respond with a direct e-mail to a newsgroup
post. My home pc went down last week and I was posting from the
library, so that may have been the problem.

Yep. I found the articles, and posted a followup to one of the
two.

I guess machining a new set of jaws out of Aluminum is not plausible.
:-)

Why not? Where do you think the jaws come from? Actually, the
Taig soft jaws are easier to make than most, because there is not the
middle step to give precise location which is present on most master
jaws. All the Taig jaws have to offer are the screws which hold them
on.

What I meant was that I don't think he has the equipment for machining
the jaws himself.

"He"? Who else came into this thread?

I was referring to the original poster.

If you have milling attachments for the lathe, you can make soft
jaws -- especially the ones for the Taig with its simple mount.

Ok. Those "teeth" seem difficult to me. I thought they were courved,
and that tolerance was very critical.


O.K. You're talking about machining entire jaws from scratch,
while I was talking about machining new "top" jaws to bolt onto a
master jaw which remains in the chuck body. Quite a different task.

The chucks designed for this (such as my Bison 3-jaw) have a
hardened "master" jaw in the body of the chuck, almost flush with the
top of the chuck surface. They also come with a hardened set of top
jaws for normal lathe use, except that if you need outside gripping
jaws, you can unbolt and reverse the top jaws without having to remove
the master jaws and replace them, as you have to do with normal
one-piece jaws. There are also available from the maker or others sets
of mild steel soft jaws, which start out with no steps at all -- full
height all the way along the length. This, you bolt to the chuck's
master jaws, and then (after blocking the jaws in place with something
appropriate), you turn them in the lathe and chuck to make a set of jaws
precisely designed to hold your workpiece -- for any project where you
are going to need to make a lot of the same thing. These can be the
right diameter to hold the workpiece precisely (more accurately than
with the standard jaws), and can be bored with a step to ensure that
each workpiece is installed to the proper depth without having to
measure each time.

Normally, such a set of soft jaws is set aside with the other
special tooling for a project, and returned to the chuck when you have
to make that again.

However, if you don't expect any more of those, you set the soft
jaws aside until you have another project which can benefit from soft
jaws, and re-bore the jaws to fit the new (obviously somewhat larger)
job. Usually, they can go through several re-borings before there is
not enough metal left to re-bore them again.

Normal two-piece jaws have a longitudinal groove on the
under surface which matches a raised rib on the master jaw, and a
cross-groove across the middle of the top jaw which mates with a raised
rib across the master, thus giving accurate location in both directions
when replacing a soft jaw on its master jaw. (You should always mark
the soft jaws so you can restore them to the same master jaw each time,
or you lose a bit of the accuracy which is otherwise possible.

The 3-jaw chuck for the Taig has only the longitudinal groove,
with the radial location being done by the bodies of the screws which
attach the top jaws to the master jaws, so they are not quite as
precisely repeatable. But they also come only with aluminum soft jaws,
not with mild steel which is common with others.

In any case, it is easy enough to mill the underside of the
stock to make jaws and drill and counterbore the holes for the screws
which attach the top jaws to the master jaws.

Making entire one-piece chuck jaws, however, is a much more
difficult task, and not what I was referring to.

Note that the "Pie" jaws are actually made from electronics
heat-sink extrusion, which is why all the fingers.

Now -- This applies only to the top jaws to go onto existing
master jaws. For making complete jaws from scratch, you need to
consider how you are going to make the scroll teeth on the bottoms of
the jaws. Each of the three jaws has the teeth at a different offset,
so the three jaws wind up close to center when the chuck is assembled.

Sounds like a CNC job to me. Or a job for an experienced machinist.

It used to be done with the jaw blanks mounted on a fixture on
an index head which was geared to the X-axis leadscrew on a milling
machine. The index head would turn fairly slowly (from a power feed),
and the gears would turn the leadscrew to provide the proper feed per
turn. A small endmill would cut the spiral threads in the back of the
jaws. (Quite probably, the fixture would hold two sets of jaws at once
to improve production and to minimize the amount of time spent cutting
air.) A similar setup would machine the scroll plate for inside the
jaws. The jaws would be shaped, and hardened, and then the two sets of
scroll teeth would be lapped -- either together, or on separate
fixtures. This would shape the teeth to allow handling the varying
radius as the jaws close or open.

Yes -- it could be one with CNC now -- but it may be more
economical to use the old machines if they still work well.

But I assume that you don't recommend using a lathe for this, correct?

I do not. The problems, as I see them, a

1) The speed of the spindle is too fast to be practical, unless
the spindle is hand cranked.

2) The coupling from the spindle to the cross-feed is not
repeatable to make the cut in multiple passes. There is no
provision for something like the half-nuts used for normal
linear threads.

3) The task really calls for a rotating tool like a small end
mill, and an appropriate tool to drive it.

[ ... ]

Note that wood, even hardwood, changes dimensions with the
ambient humidity. You can't keep any kind of precision with wood.

It shouldn't be too extreme.

A friend made a copy of an old instrument called a
"hudry-gurdy". Not the barrel organs, but rather a stringed instrument
in which the strings were bowed by the rim of a wooden wheel. Well, the
problem was that as the wood dried out, what had started with a nice
round wheel shrunk differently along the grain and across it, so it was
pressing harder on the strings during part of its rotation than during
other parts. It could not be kept in a shape good enough to produce a
steady sound.

I finally machined one for him from plexiglass, which would not
shrink. The only problem was that I put too good a polish on the rim,
and it would not hold rosin to drive the strings. :-) He solved that
with a strip of wood veneer with a diagonal join.

So -- yes, wood *does* shrink enough to be a problem as it
dries. The original ones were almost certainly made with wood which had
been dried for decades before being shaped put to use, not modern
kiln-dried wood.

Solution: Keep a spray bottom filled with water handy. :-)

Hardly. The majority of the instrument was made of wood, glued
together.

Especially since the work is not big and
heavy. And a facing operation will not pull it out of the holder. But
one can use glue if a small hole is place in the center for ventilation
so the glue will dry.

But if it is still an issue then an option is Delrin which doesn't soak
up moisture and has excellent dimensional stability.

Delrin, a set of radial grooves from the center hole to near the
outside diameter, and a vacuum pump sucking on the center hole to keep
the workpiece in place.

But probably not for stainless steel. :-)

Sounds like a complicated set-up for such a "simple" project.

Sometimes, that is the best way to go.

Or perhaps brush some liquid insulation around the perimeter of the
disks and let dry. The kind used on electrical wires. It peels off
easily.

I doubt that it would hold very well, but you are welcome to
try, and report back on the results.

It's job would be to just keep the jaws from damaging the workpiece.

Oh -- that is what aluminum soft jaws are for. When they are
machined in place in the chuck (in the lathe) the shape is such that
they will match the curve of the OD of the workpiece, so there is no
sharp edge trying to indent the workpiece.

That's if he had or could find aluminum jaws. :-)

As long as your chuck has two-piece jaws, you can make more
aluminum (or steel) jaws with a milling machine.

Enjoy,
DoN.
--
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