On 2010-09-17, George wrote:
On 17 Sep, 15:29, George wrote:
[ ... ]
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 jawchuckwhich 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.
We'll need to be reminded what the URL is of the web site.
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 thechuck
removed and there is virtually no runout. On the body of thechuck,
which is worn with dents it is essentially true.
Regards, George.
Thanks Don, I did not see your post when I replied to Jon.
I think that my post was rather late, so it is not surprising.
My
Herbert (4) lathe is big compared with nearly every other one owned
by my friends. It is about 3 metres long and the Chuck is about 25 cm
diameter. It has a 7.5 Hp motor with , - luckily, a 3 Hp option. As
you say though, it is all relative.
O.K. 25 cm is pretty close to 10" (just a little smaller).
based on the normal fit of a 6" 3-jaw to a 12" swing lathe, this would
suggest that your lathe swings 20" over the bed -- so a serious sized
lathe.
I have found a chuck for sale on Ebay which carries a very good
description, it looks and sounds just like the one I have. Is it
possible that I can find a ground adaptor somewhere. It seems to be a
quite common chuck, as there are many other Google links to them.
Here is the other chuck advert.
http://cgi.ebay.co.uk/FORKARDT-F250-...em563b fedbba
Auction # 370373745594 extracted from that long URL as easier to
cut and paste for viewing. (My newsreader does not invoke the browser
(a separate program) directly -- I have to cut and paste between them.
This is by choice, BTW. :-)
advertised in the US for quite a lot of Dollars. (over a thousand)
apart from a lot of dents and scratches on the outside, the one I have
is hardly worn on the inside.
And looking at that web site, it is an interesting design.
Instead of the usual scroll plate, there are three separate blocks with
straight-line duplications of the scroll pattern. At first I thought
that it was independent adjustment of each jaw, but it appears not to be
so. I think that you withdraw the scroll blocks by turning the key in
one direction, and then slide the jaws in to near contact with the
workpiece diameter (the "quick-adjust" feature). Then you turn the key
the other direction and the scroll plates re-engage and move each jaw
perhaps one tooth inward before the end of travel. I guess that there
is a plate with three radial slots which engage the "house" shaped
objects, one of which is labeled "53" to match the pin on which it
pivots. This transfers the motion of one scroll plate to the other two.
You'll need to find or make a back plate which mounts to your
spindle and accepts the three bolts through the chuck body to mount it.
In the last image on the auction site, there are drawings of several
such back plates. After making the plate and mounting it on the lathe
spindle, you turn the OD to be a sliding fit into the recess on the back
of the chuck (being careful to allow for cooling after machining before
measuring so you don't get a size which is too loose).
That chuck in the auction is mounted to a strange back plate.
It is not clear whether the chuck key is included -- and it is
an unusual one, too -- the key has a 14mm square *socket* instead of a
square projection.
Good Luck,
DoN.
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