Hi Folks,

I am truing the chuck jaws on the original 5" OD (Logan #431) 3-jaw chuck for my 10" Logan lathe (SN 6774A). I would like to grind the outsides of the *inside-mount* jaws. To do this, I need to pre-load them against the scroll at some particular position of the jaws, either with a ring, a hose clamp, or... read what I did for the insides of the jaws in my next post.

But what radius should the chucks be ground to? The jaws are so rounded and worn that I can't even easily tell what the radius of curvature is by looking at it, but it's something large, about the OD of the chuck body itself. Is that what it generally is when new? Is there some magic number one typically grinds to? With a large radius in the jaw, it seems I will have 6 points of contact against any part that has a smaller radius. Is this what one wants with the inside-jaws?

Does anyone (Scott Logan?) know to what dimensions the original Logan jaws were ground?

Thanks in advance for the replies.

Dan

"Daniel Koller" wrote in message
...
Hi Folks,

I am truing the chuck jaws on the original 5" OD (Logan #431) 3-jaw chuck
for my 10" Logan lathe (SN 6774A). I would like to grind the outsides of
the *inside-mount* jaws. To do this, I need to pre-load them against the
scroll at some particular position of the jaws, either with a ring, a hose
clamp, or... read what I did for the insides of the jaws in my next post.

But what radius should the chucks be ground to? The jaws are so rounded
and worn that I can't even easily tell what the radius of curvature is by
looking at it, but it's something large, about the OD of the chuck body
itself. Is that what it generally is when new? Is there some magic number
one typically grinds to? With a large radius in the jaw, it seems I will
have 6 points of contact against any part that has a smaller radius. Is
this what one wants with the inside-jaws?

Does anyone (Scott Logan?) know to what dimensions the original Logan jaws
were ground?

Thanks in advance for the replies.

Dan

I don't think the radii are that important. They should be slightly smaller
than the low end of the range each step will be used at.
You can probably ping Scott at Lathe.com.
Here's his page for regrinding jaws.
http://lathe.com/tips/chuck-jaw.htm

The old Logan chucks were made by Buck.

My Logan only had one set of jaws when I got it. After using it for years, I
happened upon a Buck SetTru probably 40 years newer.
When I put the new jaws in the old chuck, they fit like a glove.

Paul K. Dickman

"Paul K. Dickman" wrote in message
news

"Daniel Koller" wrote in message
...
Hi Folks,

I am truing the chuck jaws on the original 5" OD (Logan #431) 3-jaw
chuck for my 10" Logan lathe (SN 6774A). I would like to grind the
outsides of the *inside-mount* jaws. To do this, I need to
pre-load them against the scroll at some particular position of the
jaws, either with a ring, a hose clamp, or... read what I did for
the insides of the jaws in my next post.

But what radius should the chucks be ground to? The jaws are so
rounded and worn that I can't even easily tell what the radius of
curvature is by looking at it, but it's something large, about the
OD of the chuck body itself. Is that what it generally is when new?
Is there some magic number one typically grinds to? With a large
radius in the jaw, it seems I will have 6 points of contact against
any part that has a smaller radius. Is this what one wants with the
inside-jaws?

Does anyone (Scott Logan?) know to what dimensions the original
Logan jaws were ground?

Thanks in advance for the replies.

Dan

I don't think the radii are that important. They should be slightly
smaller than the low end of the range each step will be used at.
You can probably ping Scott at Lathe.com.
Here's his page for regrinding jaws.
http://lathe.com/tips/chuck-jaw.htm

The old Logan chucks were made by Buck.

My Logan only had one set of jaws when I got it. After using it for
years, I happened upon a Buck SetTru probably 40 years newer.
When I put the new jaws in the old chuck, they fit like a glove.

Paul K. Dickman

The jaws on my Bison 3-jaw have grooved flats on both ends.