On 15 Sep, 23:28, Jon Elson wrote:
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

Thanks very much Jon, but I am not up to cutting a new scroll, I am
afraid, I am very much an amateur. I have just found an old Forkardt
F250, 3 jaw chuck which I have carefully taken apart and cleaned and
it is in very good condition. The only problem - as far as I can see
is that the mounting is different and an adaptor plate will have to be
made. I am not sure about this, but the Forkardt seems to run on a
ground shaft about 66 mm diameter, and held on by 3 bolts, into a
rear flange. I am going to take some more photos of this, and later on
today will paste them on to the same page of my website. A more
professional view would be appreciated.

What is the pin spacing, is this the attaching studs spacing and what
does D1 mean? I put my dial indicator on the flange with the chuck
removed and there is virtually no runout. On the body of the chuck,
which is worn with dents it is essentially true.

Regards, George.