Jet lathe chuck back plate

I picked up a jet 12x40 bench lathe today. It was manufactured in 1983.
It appears to be in fairly good shape however the chuck and backing plate is
missing on this lathe. It did come with turning plate. My problem is that I
have an 8" chuck and backing plate with a 2 1/4"x8 mounting hole but it
doesn't go on the jet. It appears the jet is a 2 3/8" hole but it is an 8
thread where as all the backing plates I've been able to locate in 2 3/8ths"
are a 6 thread. Is there anyone on this forum who has had any experience
with these backing plates or have any idea where to acquire one?
Thanks,
Dick
Reply to
rhncue
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Sounds like an easy turning job to me, enlarging a 2 1/4" x 8 backing plate to 2 3/8" x 8--all you need is a metal-turning lathe with threading capabilities, and a faceplate.
Ken Grunke
Reply to
Ken Grunke
Or -- if you can do so for less -- get blank plates, perhaps with a 2" unthreaded hole (or smaller), or with no hole.
Set it up on the faceplate, clamped in place with spacers between the faceplate and your backing plate to be, so you don't cut the faceplate itself, tap it to center and clamp it down hard. Then drill the center, bore out to the proper ID, and internally thread.
But before this, set up to measure the thread pitch diameter of the spindle (3-wire method, unless you have a pitch diameter micrometer of the right range). Otherwise, as you get close, you'll have to keep unthreading the faceplate and backplate combination, reversing it, and testing it for fit on the spindle nose. With that big a pair of plates, this will get old fast. :-)
Once you have it properly threaded, and the register cut, mount it, and turn the mounting face flat, and true the OD, then turn the necessary step to center it to the lathe chuck, and mount as necessary.
Among other possible sources, Bison makes blank backing plates, as well as pre-threaded ones, and New England Brass and Tool sells them. (I've bought the pre-threaded ones from them, as I only needed to fit a 2-1/4x8 spindle which was supported. Yours *might* be, or might not. But the unthreaded blanks are cheaper, of course. :-))
At least the Jet import lathes can cut their own spindle thread. Some of the others have a metric spindle thread, but are sold here with the gearing to cut only Imperial threads, so you are stuck having to buy chucks or backplates from the vendor. :-)
Good Luck, DoN.
Reply to
DoN. Nichols
have you tried Jet?
Qn
Reply to
Quincy
Last night I kept looking for Jet tools web-site but kept coming up blank. I found it today as the company actually has a different name. Anyway I'll contact them Monday about a backing plate. On their site they have available parts but they all seem to be for newer machines. I may have to make a mounting plate anyway as I was wanting to put a set-true chuck on the lathe and they certainly won't have one of them. The spindle on this lathe looks like it was threaded for a millimeter instead of imperial threads as it is almost exactly 60 mil. however the threads are 8. Thanks for the help all and I'll get back with you all when I've got it up and running and let you know what course of action I took. One remedy that wasn't mentioned was to turn the spindle threads down to standard instead of increasing the backing plates size. I've got a few days to decide what I'm going to do. Thanks again, Dick
Reply to
rhncue
Dick..you may not be aware of it..but our very own Leigh at snipped-for-privacy@aol.com MarMachine is a Jet dealer. He posts here occasionally. You might want to drop him an email and see what he can do for you.
Gunner
"Considering the events of recent years, the world has a long way to go to regain its credibility and reputation with the US." unknown
Reply to
Gunner
I just got a hold of Jet and all they said was that I have an obsolete machine that they no longer have parts for. I asked the man what exactly the size and pitch of the spindle was and I would make my own plate and upon checking he said that it was a D-4. I told him it certainly wasn't a D-4 but a threaded spindle and he then transferred the call to someone supposedly more knowledgeable about their older equipment but that person wasn't available. Now my question to you fellows is: if this was your lathe, would you make a faceplate to fit this thread or would you turn the spindle thread down to 2 1/4-8 from 60mm-8 so as to make it standard for future use? Dick
Reply to
rhncue
My advice is to leave the spindle alone and find a back plate with the correct thread. It mat take some digging, but surely there ar a few out there. Once you put a bit to the spindle, there is no telling what you'll find out about its metallurgy and soundness.
Several factories in China made these small lathes during the '90s, and all of them vary in the details of their construction and in overall quality. The PLA kept the really good ones for its own production use, and shipped the rest to us fat Americans...
rhncue wrote:
Reply to
Tim Killian
Sounds like good advise UNLESS you can grind the threads with a toolpost grinder; if so you might consider changing the threads, especially if the lathe cannot thread the spindle nose thread.
Reply to
Nick Hull
How big is the Morse taper in the spindle? Might your threads get too shallow if you turned down to 2-1/4x8? Check that before you thread.
I understand that at one period, Jet used to turn the metric spindle thread off the spindle, heat-shrink a sleeve onto it, and rethread the OD of the sleeve *on* the lathe, to a standard thread.
Also, look at the end of the nose to see whether you can see signs of a sleeve having been heat-shrunk in place. Beware that if that is the way your machine was done, re-threading it may make the sleeve too thin, and it will split off.
I know that the Jet which we had new at work back around 1990 was a D series spindle nose -- I think a D1-4 was what it was called.
The D series (like the L-00 on my Clausing) has the advantage over a threaded spindle that you can take serious cuts in reverse without risking the chuck unscrewing from the spindle.
Good Luck, DoN.
Reply to
DoN. Nichols
Don't get you hopes up to high as in that time frame many Jets had a Metric sized spindle with inch threads..
Yes I have one and its almost 2 1/4 by 8 but mine is actuall 52mm by 8tpi. And I finally got a manual from Jet that confirmed this. My lathe is smaller at 10x24 than yours.
I think the had some 55mm by 8tpi also.
Still not hard to make your own but you really need to 3 wire your spindle and make sure you have what you are guessing you have.
Garry
Reply to
Garry

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