Chuck questions

You'd have thought if you buy a lathe advertised as coming with 2 chucks that both would fit the lathe. I was surprised enough when I saw they
were both 3-jaw s-c but when I discovered that one of them had the wrong backplate...
Anyway I now have a chuck I don't really need, it's a Pratt type 58 whatever that is. It's mounted on a backplate threaded either 25mm or 1", hard to tell which and I wondered if anyone here knows what common lathes have such a fitting ? And also where the Pratt type 58 stands quality-wise so I can decide whether to dump it via ebay or go to the effort of turning up a new backplate for it. The chuck I got that does fit the lathe it came with is an inch bigger so all things being equal I'd like to keep it. Of course I've no way of comparing the runout unless I turn up a backplate to fit it which I don't want to do unnecessarily.
Thanks,
--
Boo

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wrote:

You clearly haven't "got it" yet then - the whole point is to acquire as many toys as possible, not to use them <bg>
Regards, Tony
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Boo
I'm with Tony here you can't have enough "toys" and 3 jaw chucks seem particularly useful. If you mount it on its back coupled to a gear with a reasonable No of teeth (60?) you can quickly make a passable rapid indexer which seems to get a lot of use with me on the drill and mill anyway. I'm sure there are a million other uses I just haven't found them yet.
Regards Keith
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Well, thanks to you both for your answers but I'm still interested in knowing what lathe the backplate on the chuck is intended for ? I've just measured the thread and the id is 22.25mm with a 25.36mm id register for the spindle nose (presumeably an inch). The pitch may be 1/8th of an inch or thereabouts. Is this a match for an old Myford spindle ?
If I was going to have another 3 jaw chuck i'd prefer to get a good new one and have a backplate to fit my lathe. Then I could keep it for best/light use and also, as you suggest, for possible use with indexing gear. I don't really need two similar 3 jaws half way through their life.
--
Boo

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wrote:

Sounds too small - Myford is inch-and-an-eighth thread.
Regards, Tony.
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Tony Jeffree wrote in message ...

Earlier Myfords ML1 through ML4 used a smaller thread and a MT1 taper
Bob
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ML4s have the same thread as an ML7, i.e 1 1/8" x 8TPI; ML2s (at least the version without tumble reverse) use 7/8" x 8 TPI. ML4 has an MT2 taper, ML2 uses an MT1 taper. No imperial thread that I can identify equates to a 22.25mm ID; 7/8" = 22.25mm, but that still doesn't match any of my thread tables, metric or otherwise. Martin
--
martin<dot here>whybrow<at here>ntlworld<dot here>com



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Um, I think it must be a 1" nominal thread - the 22.25mm is the measurement of the inside of the hole through the thread and there would be the thread depth to add to that to get the thread diameter. 1.5mm odd seems a reasonable value for the depth of the thread, no ? Also I have made a more careful measurement of the thread pitch and there are 6 threads in 15.6mm making the pitch 7/64ths of an inch.
--
Boo

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Boo said

Looking at all the data supplied leads me to suggest that it is a 1" x 10tpi Whitworth.
6 threads in 15.6mm equates 2.6mm or 0.10236" and allowing for measuring discrepancy 10 tpi (0.10")sounds plausible. The depth of thread (assuming 1" nominal (25.4mm) OD) and a bore of 22.25mm calculates out to 0.062" and the theoretical depth of thread of a 10 pitch Whit form is 0.064".
JG
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And for your bonus points now "name that lathe !" :-)
--
Boo

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Boo said

Now you are asking a very different question !
For about 8 years of my earlier life (while employed by Herbert Small Tools) "Threads" were my 'thing' - everything concerning threads that came through the Export Office landed upon my desk - 'Lathes' never was :)
JG
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Boo If you have now decided that it IS 1" x 10 tpi Whitworth then that is the spindle size used on the Randa lathe of the mid thirties. The lathe was a badged Zyto but I don't know if lathes sold under their own name used that spindle size. You have not said what size the chuck register is so I can't be certain if it is exactly the same; the Randa was only about 3" centre height so if the chuck is much bigger than 4" I suspect that their must be yet another lathe that uses it as well. I know that Zyto made bigger lathes but I don't know what spindle size they used - it certainly seems small for a more modern lathe.
If you want a lathe to go with the backplate I have a Zyto badged XL in bits under my bench, it is one of theose projects that you put away for a rainy day. From the state of it it will need to be a real wet winter to get it out. Sorry, don't need another backplate or chuck it already has several.
Regards Keith
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Boo I suffered from "brain fade" last night and posted some incorrect information re the lathe type for a 1"x10 spindle thread. A clear head this morning and a bit of measuring and I hope I can correct it.
I had already mentioned the Atlas 6" which in its' older version had a 1"x8 thread; by the Mk2 version (mid 70s) this had changed to a 1"x10 spindle thread so is one definite candidate (see Tony's "lathes" website). The only other I can find listed quickly is an Advance lathe that was made in Australia between the 50s and 70s (again covered on Tony's' webpage and also here:-http://www.titaniumstudios.com/tooljunkie/advance.html
It is still as was the 1"x8 thread a popular woodworking lathe spindle thread.
I would think that both the Mk2 Atlas 6" and certainly the Advance would be fairly rare in this country so you might want to see if you can find a more popular model that it fits, particularly if you intend to try and sell it.
Regards Keith
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Well, thanks to all who answered. I do believe it may have come from a woodworking lathe as there is some evidence of wood dust on it (though there is congealed oil as well).
Anyhow, I've decided to take the advice offered and buy a new backplate for it to use on my Boxford. If I ever get a rotary table it'll be a useful size for that too...
Thanks,
--
Boo

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On Fri, 10 Jun 2005 20:48:00 GMT, "Bob Minchin"

........and all those Super 7 Series made during the past three(?) years have a spindle nose register thread of 42.5mm, to allow the passage of one inch stock. --
Chris Edwards (in deepest Dorset) ..."There must be an easier way...!"
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All together now, "Oh! Yes you do!".

Turn up a new back plate.
Pratt, Pratt & Whitney, Pratt Burnerd - they don't make 'em like that any more so I would hang on to any Pratt chuck of known model number.
1. Sooner or later you may find that half way through a job you need to do something else but would rather not risk loss of accuracy by taking the current job out of the chuck and replacing it later.
2. Sooner or later you may need to use a chuck as a clamping device on the milling table or elsewhere.
3. Sooner or later you may acquire a rotary table.
4. Sooner or later you may find a need to obtain a set of 'outside jaws'
5. Sooner or later you may find a need to obtain a set of 'soft jaws'
6. Sooner or later you may find a need ....
--
Mike Hopkins
CSME <http://goto/cheltsme>
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Boo
I'm no lathe historian but loads of old lathes had odd size spindle nose threads, the only one I know off the top of my head with 1"x8tpi is the very old Atlas 6" and I believe that changed mid fifties.
If it is that size though it is a fairly common woodworking lathe spindle size but I can't see why they would want a 3 jaw (although I'm no woodworker). Also a lot of the early "import" lathes had various size spindles depending on who was buying them, the most popular 918 was bigger at about 1.5" or 39mm (ish) so if it is reasonably modern it might be the smaller 7x series - just guessing here I have no experience of these machines.
One last try then I will leave you alone to do as you want, one of the things I did early on in my collecting was get rid of all the old "junk" as I only wanted to keep the best (I like shiny new kit) and didn't like all those dark brown and worn bits about. This was a hard (expensive) way to find out that these things would have been very useful. When Fred/Bert whoever from up the road brings his piece of junk for repair (don't think you won't get asked) I hate loading it into my nice shiny new Bernerd particularly when it turns out to be a rough casting or some super hard material that is impossible to machine. Even worse is when a (close) friend just wants to do a "quick job" and then asks for a "bit of pipe" to do up the chuck properly!!
I know you won't see it now but there will be plenty of times to come if you use the machine seriously when an additional "old" chuck will be a godsend. I certainly regret having dumped several old Crown 3 jaws for about a tenner each when they could have saved my 150 chuck some serious bother. Unless you are lucky enough to get two village idiots bidding then if someone on Ebay will pay you a reasonable amount for it then they might also have learnt this lesson?
Hope you don't mind me trying once more to convince you - wish someone had told me. I'll let you get on with what you want to do now.
Best regards Keith
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