Further testing needed ...

[Snag]

I got the back plate finished for the 3 inch chuck and I'm a bit
disappointed at my initial testing results . I've measured .015 runout
on a piece of 1/2 inch stock that I'm pretty sure is straight . Might be
the jaws since the chuck body indicates about .004 near the face . These
are the inside step jaws and the clamping surface is not very long so
that may be part of it . I'll be installing the outside step jaws
tomorrow and checking them - it came with 2 sets of those , one which
matches the chuck s/n and one that doesn't . The inside step set I have
installed do not match numbers ... aaahhh , what should I expect for a
$10 yard sale purchase !
Actually , it may be as simple as regrinding the mismatched jaw sets
to match this chuck . I have a little time to play with it , got no
"other people's projects" in the shop right now .

[Snag]

  I got the back plate finished for the 3 inch chuck and I'm a bit
disappointed at my initial testing results . I've measured .015 runout
on a piece of 1/2 inch stock that I'm pretty sure is straight . Might be
the jaws since the chuck body indicates about .004 near the face . These
are the inside step jaws and the clamping surface is not very long so
that may be part of it . I'll be installing the outside step jaws
tomorrow and checking them - it came with 2 sets of those , one which
matches the chuck s/n and one that doesn't . The inside step set I have
installed do not match numbers ... aaahhh , what should I expect for a
$10 yard sale purchase !
  Actually , it may be as simple as regrinding the mismatched jaw sets
to match this chuck . I have a little time to play with it , got no
"other people's projects" in the shop right now .

Further testing having been completed the chuck has runout with all 3
sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing straight with the ways ...
looks like it's time to set up the toolpost grinder .
So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece of
stock ?

[Bob La Londe]

   I got the back plate finished for the 3 inch chuck and I'm a bit
disappointed at my initial testing results . I've measured .015 runout
on a piece of 1/2 inch stock that I'm pretty sure is straight . Might
be the jaws since the chuck body indicates about .004 near the face .
These are the inside step jaws and the clamping surface is not very
long so that may be part of it . I'll be installing the outside step
jaws tomorrow and checking them - it came with 2 sets of those , one
which matches the chuck s/n and one that doesn't . The inside step set
I have installed do not match numbers ... aaahhh , what should I
expect for a $10 yard sale purchase !
   Actually , it may be as simple as regrinding the mismatched jaw
sets to match this chuck . I have a little time to play with it , got
no "other people's projects" in the shop right now .

  Further testing having been completed the chuck has runout with all 3
sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing  straight with the ways ...
looks like it's time to set up the toolpost grinder .
  So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece of
stock ?

Does a known straight rod point straight and parallel if is directly in
a collet that fits in the native spindle bore? If not then level
(untwist) your lathe before doing anything else.

Which pinion to use? I have no idea. Whenever I use a scroll chuck I
try to do all operations that are important to be concentric in a single
setup so runout is not a big deal. If I can't and close is good enough
sometimes I wing it or carefully clock the part, but if it must be dead
nuts I either dial in the set tru for that size or use the 4 jaw.

I expect when I get the turret/collet lathe finished I'll do most of the
close enough repetitive work in it.

[Snag]

Post by Bob La Londe

   I got the back plate finished for the 3 inch chuck and I'm a bit
disappointed at my initial testing results . I've measured .015
runout on a piece of 1/2 inch stock that I'm pretty sure is straight
. Might be the jaws since the chuck body indicates about .004 near
the face . These are the inside step jaws and the clamping surface is
not very long so that may be part of it . I'll be installing the
outside step jaws tomorrow and checking them - it came with 2 sets of
those , one which matches the chuck s/n and one that doesn't . The
inside step set I have installed do not match numbers ... aaahhh ,
what should I expect for a $10 yard sale purchase !
   Actually , it may be as simple as regrinding the mismatched jaw
sets to match this chuck . I have a little time to play with it , got
no "other people's projects" in the shop right now .

   Further testing having been completed the chuck has runout with all
3 sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing  straight with the ways ...
looks like it's time to set up the toolpost grinder .
   So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece
of stock ?

Does a known straight rod point straight and parallel if is directly in
a collet that fits in the native spindle bore?  If not then level
(untwist) your lathe before doing anything else.

The lathe is level and no twist as measured with a .005"/foot
precision level . I have no collets to test with , but with the 5" 3 jaw
I get no measurable taper .

[David Billington]

   I got the back plate finished for the 3 inch chuck and I'm a bit
disappointed at my initial testing results . I've measured .015
runout on a piece of 1/2 inch stock that I'm pretty sure is straight
. Might be the jaws since the chuck body indicates about .004 near
the face . These are the inside step jaws and the clamping surface is
not very long so that may be part of it . I'll be installing the
outside step jaws tomorrow and checking them - it came with 2 sets of
those , one which matches the chuck s/n and one that doesn't . The
inside step set I have installed do not match numbers ... aaahhh ,
what should I expect for a $10 yard sale purchase !
   Actually , it may be as simple as regrinding the mismatched jaw
sets to match this chuck . I have a little time to play with it , got
no "other people's projects" in the shop right now .

  Further testing having been completed the chuck has runout with all
3 sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing  straight with the ways ...
looks like it's time to set up the toolpost grinder .
  So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece
of stock ?

Does it have a pinion with a 0 next it? All my 3 jaw self centring
chucks have one and is supposed to be the pinion which result in the
minimum runout.

[Snag]

Post by David Billington

   I got the back plate finished for the 3 inch chuck and I'm a bit
disappointed at my initial testing results . I've measured .015
runout on a piece of 1/2 inch stock that I'm pretty sure is straight
. Might be the jaws since the chuck body indicates about .004 near
the face . These are the inside step jaws and the clamping surface is
not very long so that may be part of it . I'll be installing the
outside step jaws tomorrow and checking them - it came with 2 sets of
those , one which matches the chuck s/n and one that doesn't . The
inside step set I have installed do not match numbers ... aaahhh ,
what should I expect for a $10 yard sale purchase !
   Actually , it may be as simple as regrinding the mismatched jaw
sets to match this chuck . I have a little time to play with it , got
no "other people's projects" in the shop right now .

  Further testing having been completed the chuck has runout with all
3 sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing  straight with the ways ...
looks like it's time to set up the toolpost grinder .
  So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece
of stock ?

Does it have a pinion with a 0 next it? All my 3 jaw self centring
chucks have one and is supposed to be the pinion which result in the
minimum runout.

I'll have to look and see . I haven't noticed any markings next to
one of the pinions .

[Jim Wilkins]

"Snag" wrote in message news:vcn5gc$1n35p$***@dont-email.me...

Further testing having been completed the chuck has runout with all 3
sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing straight with the ways ...
looks like it's time to set up the toolpost grinder .
So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece of
stock ?

[Snag]

  Further testing having been completed the chuck has runout with all 3
sets of jaws of around .007" . Chuck body is more like .002-.003 . A
known straight 1/2" rod is not pointing  straight with the ways ...
looks like it's time to set up the toolpost grinder .
  So it looks like maybe a cheap chuck , though well made . Fit and
finish are good , everything fits as it should and the scroll moves
smoothly with all 3 pinions . Which brings me to a question - since
there's more than one pinion is it going to make any difference which
one I use ? Do I need to give 'em all 3 a twist when I mount a piece of
stock ?

------------------

In the new Mongolian 6-jaw I cleaned up the scroll plate fit quite
closely on its pivot in the body, too tight until it was cleaned. I
don't think it could shift away from whichever pinion I tightened.
Perhaps it might in a worn chuck.
------------------

I don't think this chuck has much wear . All the jaws look "new" but
that doesn't always mean much . I was told the original owner was into
woodworking , which doesn't necessarily require the precision needed for
metal working . By tightening all 3 pinions I have gotten it down to
average .004" , which is pretty close to my original equipment 5" chuck
. I can live with that ...

[Jim Wilkins]

"Snag" wrote in message news:vcnitb$1p0o6$***@dont-email.me...

I don't think this chuck has much wear . All the jaws look "new" but
that doesn't always mean much . I was told the original owner was into
woodworking , which doesn't necessarily require the precision needed for
metal working . By tightening all 3 pinions I have gotten it down to
average .004" , which is pretty close to my original equipment 5" chuck
. I can live with that ...
----------------------------------------

I've considered using a bearing press disk set to measure the jaw inner face
runout at several diameters, to see if it varied due to wear or errors in
the scroll or was a constant error of the jaw faces, which might be
corrected on a surface grinder. A 3-jaw will grip evenly if the disk isn't
quite round.

For a 6-jaw that won't a stepped cone of plastic or a trued lawnmower blade
balancer could have enough flex to allow all jaws to clamp tightly, then
measure runout on the outer jaw surfaces and subtract their thicknesses, a
job for a spreadsheet.

I haven't tried this because I have 5C collets for precise work, a Set-Tru,
and lower cost 3 and 6 jaw chucks on 5C mounts that can be moved between
lathe and mill without unclamping the workpiece. Since I design what I make
some surface can usually be sized to fit a collet or mandrel for second
operations or later mods.

It appears that tubing thin and flexible enough to need a 6-jaw is also
flexible enough to fit a shaft despite jaw runout, for instance bearing
spacer rings. I haven't yet had a job that would require fitted pie jaws or
a pot collet.
jsw