I'm about to buy a 6" independent 4-jaw lathe chuck. ENCO has their
free shipping promo on this month, so I was looking there.

They have a no-name with threaded mount for $99.95 (ENCO #271-6382):
http://www.use-enco.com/pdfs/157.PDF

or

Bison plain back for $156.95 (ENCO #240-3064):
http://www.use-enco.com/pdfs/160.PDF
& it's "semi-finished" threaded back plate for $43.95 (BTW it says this
back plate is for self-centering scroll chucks, do you think it'll work
with the independent jaws chuck? There's no finished back plate shown
explicitly for the independent jaws chucks.)

I do believe that you get what you pay for, but I also believe in buying
what I _need_, even if it's not always the "best". So, what does the
$200 Bison have or do that the $100 no-name doesn't? With an
independent 4-jaw, all you really need is that the jaws are parallel to
the spindle axis, right? How much worse will the no-name be than the
Bison in this regard?

I expect that the chuck will get very little use, so durability is not
something I need.

If I get the Bison, how fussy would I have to be in finishing the
semi-finished back plate? My lathe experience was in high school shop,
45 years ago.

I hope that this doesn't provoke a debate or too many rants about
Chinese crap. My apologies in advance if it does ;-)
Bob

On Sun, 24 Aug 2003 16:33:02 -0400, Bob Engelhardt wrote:
I'm about to buy a 6" independent 4-jaw lathe chuck. ENCO has their
free shipping promo on this month, so I was looking there.

They have a no-name with threaded mount for $99.95 (ENCO #271-6382):
http://www.use-enco.com/pdfs/157.PDF

or

Bison plain back for $156.95 (ENCO #240-3064):
http://www.use-enco.com/pdfs/160.PDF
& it's "semi-finished" threaded back plate for $43.95 (BTW it says this
back plate is for self-centering scroll chucks, do you think it'll work
with the independent jaws chuck? There's no finished back plate shown
explicitly for the independent jaws chucks.)

I do believe that you get what you pay for, but I also believe in buying
what I _need_, even if it's not always the "best". So, what does the
$200 Bison have or do that the $100 no-name doesn't? With an
independent 4-jaw, all you really need is that the jaws are parallel to
the spindle axis, right? How much worse will the no-name be than the
Bison in this regard?

The no name threaded chuck leaves you at the mercy of the
chuck manufacturer *and* your lathe manufacturer as far as
it being concentric, and with the face and jaw slots perpendicular
to the spindle axis. If it isn't, there isn't a whole lot you can
do about it. You can grind the jaws in place to correct for a
small amount of error, but that generally isn't desirable.

With the plain back chuck (and Bison is good) it is up to you
to machine the back plate true. But since you'll be doing it on
*your* lathe, it should wind up perfectly perpendicular to your
lathe axis. How could it not? So that's generally the better
way to go. It allows you to remove any tolerance stack up or
manufacturing errors that your lathe manufacturer or the
chuck manufacturer may have made.


If I get the Bison, how fussy would I have to be in finishing the
semi-finished back plate? My lathe experience was in high school shop,
45 years ago.

You have to face off the semi-finished backplate, it is already
threaded for your spindle, and then spot and drill it for the chuck
mounting bolts. It isn't a particularly fussy job, and you want a
little slop in the mounting holes so you can adjust the chuck to
run dead true when you mount it.

Gary

"Bob Engelhardt" wrote:
I'm about to buy a 6" independent 4-jaw lathe chuck. ENCO has their
free shipping promo on this month, so I was looking there.

They have a no-name with threaded mount for $99.95 (ENCO #271-6382):
http://www.use-enco.com/pdfs/157.PDF

or

Bison plain back for $156.95 (ENCO #240-3064):
http://www.use-enco.com/pdfs/160.PDF


Hello Bob,

I have a Bison 6-1/4" (it's actually 160mm) independent 4-jaw chuck. I think
you will be very pleased if you bought this chuck. The no-name (usually
Chinese) chucks are hit-or-miss...you really have no idea what you'll be
getting. The Bisons are inspected and certified (and very well made).

In any case, if you decide to go with the no-name, then you should skip the
one with the threaded back and get the plain back #271-6005 (currently on
sale for $59.99). That way you can machine your own back plate on YOUR OWN
lathe. This will ensure that at least the chuck mounting surface is
concentric with--and perpendicular to--your spindle.


& it's "semi-finished" threaded back plate for $43.95 (BTW it says
this back plate is for self-centering scroll chucks, do you think
it'll work with the independent jaws chuck? There's no finished
back plate shown explicitly for the independent jaws chucks.)

It'll work alright...after you machine off about 8 lbs of cast iron! You
see, many 4-jaw independent chucks (including the Bison 6") do not use full
back plates. They use something more like a "back plug" that fits into a
recess in the back of the chuck. The mounting bolts are positioned near the
center axis of the chuck which is why the adapter plate doen't need to
extend to the full diameter of the chuck. (Whereas, on a scroll chuck, the
bolt are near the outer periphery in order to clear the internal scroll
mechanism.)

According to Bison's tech manual, the 160mm 4-jaw independent chuck requires
an adapter only 82.55mm (3-1/4") in diameter. So all you really need is a
piece of machinable steel 3-3/8" in diameter and roughly 1-1/2" long (length
depending on your actual spindle mount requirements). Of course, you can use
seasoned cast iron if you can find a piece like that.

(Note: this info in the last two paragraphs are specifically for the Bison
6-1/4" chuck. I don't know the requirments for the no-name plain back--and
you probably won't either until you get it. Some 4-jaw independents do
require full-sized back plates.)


I do believe that you get what you pay for, but I also believe in
buying what I _need_, even if it's not always the "best". So,
what does the $200 Bison have or do that the $100 no-name doesn't?
With an independent 4-jaw, all you really need is that the jaws
are parallel to the spindle axis, right? How much worse will the
no-name be than the Bison in this regard?

The Bison is machined to higher quality standards and is inspected and
certified during QA. Presumably, those chucks that don't pass inspection
never make it to market.

Of course, that doesn't mean you can't get a no-name that is as accurate as
a Bison (or other quality branded chuck). But I don't think you'll really
know what you're getting until you have it mounted on your lathe.


I expect that the chuck will get very little use, so durability
is not something I need.

You might find yourself using it more than you currently expect. The 4-jaw
independent has the potential to always be more accurate than a scroll
chuck. Once you get a good one and become experienced with it, you'll find
it doesn't take long to get it set-up.


If I get the Bison, how fussy would I have to be in finishing the
semi-finished back plate?

You should be as fussy as you can, of course. Seriously, the mating surfaces
for the spindle shoulder and for the chuck recess should be very well
finished and a very close fit. Or, as Bison says: "Centering surfaces of the
adapters should be fayed against the chuck body with the clearance the
smallest possible."

Some argue that the threads on threaded spindles are also partly responsible
for keeping the adapter (and chuck) located with respect to the spindle, so
they should also be well-finished and of close tolerance. You should make a
mock spindle plug that is an exact copy of the threaded portion of your
spindle nose, including the locating shoulder. That way you can test the fit
of your adapter while you are machining it (you obviously do not want to be
taking it off during the machining process to test against your actual
spindle nose).

Regards,
Michael

On Mon, 25 Aug 2003 06:12:59 GMT, "DeepDiver"
wrote:

snip
Some argue that the threads on threaded spindles are also partly responsible
for keeping the adapter (and chuck) located with respect to the spindle, so
they should also be well-finished and of close tolerance. You should make a
mock spindle plug that is an exact copy of the threaded portion of your
spindle nose, including the locating shoulder. That way you can test the fit
of your adapter while you are machining it (you obviously do not want to be
taking it off during the machining process to test against your actual
spindle nose).

The fitting of a chuck backplate to a threaded spindle has been
discussed here a number of times. Close fitting threads (short of any
binding) are good but the critical point of fit is where the back
plate goes over the unthreaded portion of the spindle just past the
end of the thread (the counter? I can't seem to come up with the right
word) and then contacts the face of the shoulder behind the thread.
Having about .0005 or .001 clearance there and full contact with the
shoulder provides very positive and repeatable locating.

If you have another pretty good chuck, a good way to fit a back plate
is to mount the rough casting facing backwards in that chuck (3 or 4
jaw, don't unchuck it for any reason until finished). Then bore it,
cut the thread, face the back shoulder perpendicular to the thread,
and chamfer the shoulder (both inside and outside edges).

Then start relieving the thread to the depth (a little extra is OK on
the depth to avoid thread bind) and diameter (critical!) that will fit
the counter. When you get mega close, simply take the chuck off and
turn it around to test the fit.

When the counter recess in the back plate will wipe blueing off the
counter shoulder, quit cutting, and polish it well. With any luck it
will wipe the blueing on both the counter O.D. and the shoulder face
and you're done with the critical part.

You may also want to take clean up cuts on the outside of the part
that goes over the spindle and the back of the plate. If you see
small holes or pockets don't try to go deep enough to get a clean
surface, you may run out of material first.

When you can wring the backplate down against the shoulder by hand you
are ready to turn it to the needed O.D. and clean up the face. That
can be a challenging cut, you may have to change speeds part way
through the cut to reduce the surface speed if it starts chattering.

Dirty work? You have not seen dirty work on a lathe until you have
machined a rough casting. Especially the cheap imports. There are no
chips, just powdered graphite and dirt.

For the Bison with the back recess, fit the O.D. to the recess and
chamfer the edge to avoid bind. Maybe even cut a very slight taper
towards the front so that the back plate is pulled into the recess and
flush against the chuck by the chuck mounting screws. Steal the
mounting bolt layout with a close fitting center punch through the
bolt holes.

You'll feel good about yourself every time you mount a chuck with a
well fitted backplate that you did yourself. And it will repay the
time spent almost every time you use it.



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just past the
end of the thread (the counter? I can't seem to come up with the right
word) and then contacts the face of the shoulder behind the thread.

The register.

Gary Repesh

.... the counter? I can't seem to come up with the right
word ...


It's called the "register".

Bob, I have a D-4 mount ENCO 3 Jaw chuck and it works fine. But since
its a 4 jaw independent chuck you are purchasing it really doesn't
make a lot of sense to worry about the alinement of the back plate to
the chuck, as anything you chuck up will need to be centered anyway
.

I also have a Bison 5C collet chuck and I love it! B.G.






Bob Engelhardt wrote in message ...
I'm about to buy a 6" independent 4-jaw lathe chuck. ENCO has their
free shipping promo on this month, so I was looking there.

They have a no-name with threaded mount for $99.95 (ENCO #271-6382):
http://www.use-enco.com/pdfs/157.PDF

or

Bison plain back for $156.95 (ENCO #240-3064):
http://www.use-enco.com/pdfs/160.PDF
& it's "semi-finished" threaded back plate for $43.95 (BTW it says this
back plate is for self-centering scroll chucks, do you think it'll work
with the independent jaws chuck? There's no finished back plate shown
explicitly for the independent jaws chucks.)

I do believe that you get what you pay for, but I also believe in buying
what I _need_, even if it's not always the "best". So, what does the
$200 Bison have or do that the $100 no-name doesn't? With an
independent 4-jaw, all you really need is that the jaws are parallel to
the spindle axis, right? How much worse will the no-name be than the
Bison in this regard?

I expect that the chuck will get very little use, so durability is not
something I need.

If I get the Bison, how fussy would I have to be in finishing the
semi-finished back plate? My lathe experience was in high school shop,
45 years ago.

I hope that this doesn't provoke a debate or too many rants about
Chinese crap. My apologies in advance if it does ;-)
Bob

Thanks to all for your advice. In my heart I knew that the Bison was
the way to go. I "afforded" it by using some of my Special Private
Money (SPM).

My wife and I each year get some SPM, kind of like a bonus. This is
off-budget money that does not have to be accounted for and it's use
does not require any justification. I use mine for things I can't
ordinarily justify. E.g., things that might be used very infrequently
(good power washer), or are much more than I _need_ (NEXGEN welding
helmet).

So, the chuck's been ordered and now I need to practice some lathe-ing
before I cut into that $40 back plate.

Bob