On 09/15/2010 01:32 AM, George wrote:
Hello again,

I have a 60 year old Herbert preoptive Lathe. It is quite huge and I
have a chuck with a very bad case of worn out scroll. My question is:
is it possible to replace the scroll and the jaw carriers, or what
ever they are called. or would it be easier to get a whole chuck, -
Easier? Sure, replacing the whole chuck is easier....
But, machining a new scroll is not very difficult. The main thing is
you need to be able to replicate whatever the spiral thread pitch is on
the chuck, unless you will be replacing the lower jaws, too. Your lathe
may or may not be able to match that thread pitch with whatever
settings are available. Depending on how the scroll is turned by the
pinions, that can be the more difficult part. Often they have bevel
gear teeth cut in the edge of the scroll.

Making new lower jaws may be more difficult, as they need to be a very
fine fit into the chuck body, and have a number of bearing surfaces that
need to be ground.
there is no runout on the body of the chuck? I get runout that varies
over about 20 thou, depending on which bit of the scroll is in use.
What about the chances of finding a 4 jaw that would fit on the 3 stud
fixing.
I assume this is a D1-x camlock mount, when you talk about these pins.
These are still in current use, and many chucks, backplates and etc. can
be found in tool catalogs. Just measure the pin spacing and you
should be able to match the correct D1 size.

Jon