Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine compared to the Smithy 3in 1 I had. It came two three jaw chucks and each of them had 20 mill run out. I bought a new cheap 3 jaw and was thrilled to see it had about 2 mill run out until the 2" diam Al rod jammed when I was parting it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.

The new chuck (Christmas present) is arriving in a day or two and it is supposed to be a step up from the cheap ones. I am also going to be way more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?

On Fri, 04 Jan 2013 15:35:52 -0800, d32 wrote:

Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine
compared to the Smithy 3in 1 I had. It came two three jaw chucks and
each of them had 20 mill run out. I bought a new cheap 3 jaw and was
thrilled to see it had about 2 mill run out until the 2" diam Al rod
jammed when I was parting it out. Now I have 3 cheap 3 jaw chucks with
20 mill run out.

The new chuck (Christmas present) is arriving in a day or two and it is
supposed to be a step up from the cheap ones. I am also going to be way
more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?

Uh -- start with a cheap chuck that's already beaten up?



--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

"d32" wrote in message
...
Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine compared
to the Smithy 3in 1 I had. It came two three jaw chucks and each of them
had 20 mill run out. I bought a new cheap 3 jaw and was thrilled to see it
had about 2 mill run out until the 2" diam Al rod jammed when I was parting
it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.

The new chuck (Christmas present) is arriving in a day or two and it is
supposed to be a step up from the cheap ones. I am also going to be way
more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?
================================================== ==

I bleeve you can grind the jaws pretty simply for zero runout. Dumont-type
grinder (or improvisation) in tailstock.
--
EA

On Jan 4, 4:13*pm, "Existential Angst" wrote:
"d32" wrote in message

...
Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. *Sweet machine compared
to the Smithy 3in 1 I had. * It came two three jaw chucks and each of them
had 20 mill run out. * I bought a new cheap 3 jaw and was thrilled to see it
had about 2 mill run out until the 2" diam Al rod jammed when I was parting
it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.

The new chuck (Christmas present) *is arriving in a day or two and it is
supposed to be a step up from the cheap ones. *I am also going to be way
more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?
================================================== ==

I bleeve you can grind the jaws pretty simply for zero runout. Dumont-type
grinder (or improvisation) in tailstock.
--
EA

http://www.youtube.com/watch?v=IAtASZxDaf4

"d32" wrote in message
...

Anyone have some rule of thumb for cut off operations?

When in doubt, finish on the bandsaw.

"d32" wrote in message
...
Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine compared
to the Smithy 3in 1 I had. It came two three jaw chucks and each of them
had 20 mill run out. I bought a new cheap 3 jaw and was thrilled to see it
had about 2 mill run out until the 2" diam Al rod jammed when I was parting
it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.

The new chuck (Christmas present) is arriving in a day or two and it is
supposed to be a step up from the cheap ones. I am also going to be way
more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?
===========================================

I'm not really a fan of parting, except on tubing. Thick solid stuff is a
pita.
Imo, better to cut thick stuff on a saw (band, RAS, abrasive, whatever does
the job), and then face it.
But then, ahm no 'spert, I just get thru the day.

Lest the 'sperts don't reply:

Don't have the parting tool too low below center.
Don't have it stick out any farther than necessary.
Be prepared to move the carriage in X bec of tool drift -- I've never parted
anything that didn't wind up convex or concave, unless it's very small
diameter, or tubing.

Make sure you have the right rake etc on the tool.
Use oil, coolant, make sure rpm is appropriate for mat'l, diameter.
Some people don't realize that even tho alum is easy to work, it's low
melting point/gumminess can cause its own problems with tool breakage. So
watch the rpm on large diam stuff.
--
EA

On Friday, January 4, 2013 5:35:52 PM UTC-6, d32 wrote:
Anyone else had trouble with the $150 three jaw chuck?



About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine compared to the Smithy 3in 1 I had. It came two three jaw chucks and each of them had 20 mill run out. I bought a new cheap 3 jaw and was thrilled to see it had about 2 mill run out until the 2" diam Al rod jammed when I was parting it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.



The new chuck (Christmas present) is arriving in a day or two and it is supposed to be a step up from the cheap ones. I am also going to be way more carful doing cut off operations.



Anyone have some rule of thumb for cut off operations?

You can modify the back plate to make it into an adjust true type chuck... So VERY easily.

Turn the back plate smaller than the mounting register on the chuck, make sure you have clearance for the mounting bolts, and add adjuster screws to dial it into position..
Even easier than making a new mounting plate for the new chuck..

On Fri, 4 Jan 2013 15:35:52 -0800 (PST), d32
wrote:

Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine compared to the Smithy 3in 1 I had. It came two three jaw chucks and each of them had 20 mill run out. I bought a new cheap 3 jaw and was thrilled to see it had about 2 mill run out until the 2" diam Al rod jammed when I was parting it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.

The new chuck (Christmas present) is arriving in a day or two and it is supposed to be a step up from the cheap ones. I am also going to be way more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?
I can't see how a chuck can go from .002" runout to .02" and can't
be adjusted back to the original .002" I don't know what your chuck
looks like but it probably mounts to a backplate that in turn mounts
to the lathe spindle. If this is the case then loosening the bolts
that attach the chuck to the backplate and tapping the chuck with a
soft hammer or similar back to center is the solution. Make sure to
re-tighten the bolts. Do you have a link to a picture of your chuck? I
have more than once converted standard chucks to adjustable chucks. It
is pretty easy.
Eric

"Existential Angst" wrote
Be prepared to move the carriage in X bec of tool drift -- I've
never parted anything that didn't wind up convex or concave, unless
it's very small diameter, or tubing.

Whenever I have to loosen the toolpost or compound I reset it square
with the parting tool holder pressed against the end of the spindle.

"Jim Wilkins" wrote in message
...
"Existential Angst" wrote
Be prepared to move the carriage in X bec of tool drift -- I've never
parted anything that didn't wind up convex or concave, unless it's very
small diameter, or tubing.

Whenever I have to loosen the toolpost or compound I reset it square with
the parting tool holder pressed against the end of the spindle.

Oh yeah, I knew I was forgetting something.
Which is proly why all my **** comes out convex/concave..... lol
--
EA

On Jan 4, 5:20*pm, "Existential Angst" wrote:
"Jim Wilkins" wrote in message

...

"Existential Angst" wrote
Be prepared to move the carriage in X bec of tool drift -- I've never
parted anything that didn't wind up convex or concave, unless it's very
small diameter, or tubing.

Whenever I have to loosen the toolpost or compound I reset it square with
the parting tool holder pressed against the end of the spindle.

Oh yeah, I knew I was forgetting something.
Which is proly why all my **** comes out convex/concave..... * lol
--
EA









Bull****. As soon as it does you're smart enough now to know what the
problem is and fix it.

"Existential Angst" wrote in message
...
"Jim Wilkins" wrote in message
...
"Existential Angst" wrote
Be prepared to move the carriage in X bec of tool drift -- I've
never parted anything that didn't wind up convex or concave,
unless it's very small diameter, or tubing.

Whenever I have to loosen the toolpost or compound I reset it
square with the parting tool holder pressed against the end of the
spindle.

Oh yeah, I knew I was forgetting something.
Which is proly why all my **** comes out convex/concave..... lol
--
EA

I should add that my parting tool holder is hardened Chromoly,
precision-ground to aerospace tolerances by elves in Switzerland.

Very large, well-armed elves.

If yours came from a Chicom prison factory the blade may not be so
precisely parallel to the end of the holder.

"Existential Angst" wrote in message ...
"Jim Wilkins" wrote in message
...
"Existential Angst" wrote
Be prepared to move the carriage in X bec of tool drift -- I've never
parted anything that didn't wind up convex or concave, unless it's very
small diameter, or tubing.

Whenever I have to loosen the toolpost or compound I reset it square with
the parting tool holder pressed against the end of the spindle.


Indicate it parallel to the axis travel, unless you are already certain that the spindle is accurately trammed to the cross slide.

Oh yeah, I knew I was forgetting something.
Which is proly why all my **** comes out convex/concave..... lol
--
EA

"PrecisionmachinisT" wrote in message
news:3fedne8Db41RB3rNnZ2dnUVZ_o6dnZ2d@scnresearch. com...

"Existential Angst" wrote in message
...
"Jim Wilkins" wrote in message
Whenever I have to loosen the toolpost or compound I reset it
square with
the parting tool holder pressed against the end of the spindle.


Indicate it parallel to the axis travel, unless you are already
certain that the spindle is accurately trammed to the cross slide.

If the cross slide axis isn't square to the spindle the cut will still
be concave or convex. My lathe is good old American iron and suffers
from wear and student abuse rather than poor manufacturing.

I bevel the end of the cutoff bit -very- slightly, as little as
possible by hand grinding really, to leave the teat on the work, the
opposite of conventional advice. Then if the bevel deflects the cut
the work has extra metal I can remove rather than being spoiled, and
the concave stock end is easily faced square before making the next
piece, and doesn't have a protrusion that deflects the center drill.
jsw

All

There are some great ideas here. Thanks!

I like the idea of grinding the jaws square. I am looking at making a tool post mount for my die grinder. Bearing seem to be pretty good and it should work but I will have to make sure the jaws are indexed or bad things will happen.

The other idea I like is to turn down the centering shoulder on the mounting plate then re set center, I am a bit worried the chuck will move as the only thing holding it is friction.

Thanks all

On Fri, 4 Jan 2013 15:35:52 -0800 (PST), d32
wrote:

Anyone else had trouble with the $150 three jaw chuck?

About 4 years ago I bought a used 13 X 40 Jet lathe. Sweet machine compared to the Smithy 3in 1 I had. It came two three jaw chucks and each of them had 20 mill run out. I bought a new cheap 3 jaw and was thrilled to see it had about 2 mill run out until the 2" diam Al rod jammed when I was parting it out. Now I have 3 cheap 3 jaw chucks with 20 mill run out.

The new chuck (Christmas present) is arriving in a day or two and it is supposed to be a step up from the cheap ones. I am also going to be way more carful doing cut off operations.

Anyone have some rule of thumb for cut off operations?


I could never part off work with any real sucess on any manual lathe.
Now on my CNC I have very good luck. Mostly I think because I no
longer use a HSS cuoff blade. I'm using Manchester carbide inserts.
Exspensive at $18.xx each, but I think the complex chip contol molded
into the top of them makes parting off work way better than any
sharpen job you can do on a HSS blade.

Remove 333 to reply.
Randy