Adapter for Smaller Chuck to Larger Spindle
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  1. #1
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    Default Adapter for Smaller Chuck to Larger Spindle

    Gentlemen;

    I'd like to buy, or make a spindle adapter to allow mounting of a smaller (and older) 3-Jaw chuck with a 1 1/2" x 8 thread to a larger spindle with a 2 1/4" x 8 thread. This may have already been done a million times (?), I just can't find the correct reference in the archives. The general concept I have is as depicted in this attachement:

    adapter.jpg

    If I have to make one, I'd like some advice on the following:

    1. General Configuration
    2. Material spec

    Intuition tells me it needs to be as short as possible, while still able to carry whatever load is applied. As always, thanks in advance for comments!

    Lou 0.

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    Would go a different route.
    Make or buy a chuck adapted for the larger sized thread. (Flat plate ,OD same as the small chuck threaded to accept the lathe spindle)

    Remove the back plate off the small chuck
    Drill and tap the plate to the same bolt pattern as your small chuck uses to hold the back plate.
    Bolt the small chuck directly to the face plate....
    Best if possible to machine the face of the plate to have a register to locate the small chuck when mounted.
    Cheers Ross

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    Thanks for the reply, Ross. The small chuck in question only has the threaded mount (see pic attached). I do have larger chucks that fit perfectly, but are really heavy for small stuff, hence the smaller chuck idea. I don't want to drill any holes in the back of this old chuck just to mount it on a plain faceplate. So maybe I'm misunderstanding you?
    Lou O.

    img_20200312_140617185.jpg

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    Quote Originally Posted by louosten View Post
    Thanks for the reply, Ross. The small chuck in question only has the threaded mount (see pic attached). I do have larger chucks that fit perfectly, but are really heavy for small stuff, hence the smaller chuck idea. I don't want to drill any holes in the back of this old chuck just to mount it on a plain faceplate. So maybe I'm misunderstanding you?
    Lou O.

    img_20200312_140617185.jpg
    i guess that if you take out the three screws you will find that it is on fact a sort of back plate.

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    Quote Originally Posted by janvanruth View Post
    i guess that if you take out the three screws you will find that it is on fact a sort of back plate.
    Yes. And tightly fitted, as well. Mebbe even a shrink-together "interference" fit.

    That's a nuisance to pull. But a looong way from "integral back" permanent.

    What Ross - and Jan - have suggested is simply "the way", not theory nor guesswork.

    We ALL do that...and always have done, IOW. No "magic" to it.

    JFDI.

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    Yep, guaranteed that chuck comes apart on the back....gotta be a way to get the scroll in there you know.....
    Cheers Ross

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    Quote Originally Posted by AlfaGTA View Post
    Yep, guaranteed that chuck comes apart on the back....gotta be a way to get the scroll in there you know.....
    Cheers Ross
    Meahh.. "Scroll operated" is actually a separate travesty in any case...

    I mean.. if yah actually have some compelling NEED to HALF-grip round stock off-center?

    Why leave it to fate, wear, damage, poor QC and other random happenstance when yah can just dial-in EXACTLY however much intentional TIR error yah WANT with a 4-J and have double the grip so it STAYS as off-centre as you commanded it be?

    Put another way?

    If you MUST run a scroll-operated intended-to-be-self-centering chuck?

    Salvaged one with an age of wear and prangs on it arredy is a poor gamble.

    Budget is tight? Go order NEW and to tight tolerance value-for-money from ToS Svitavy.

    Chucks | TOS Svitavy, a.s.

    You won't likely need to do it twice. Cheaper than ruint work over the next 10 or 20 years?

    Could was. Česká Republika folk know their metalworking.



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    I agree with those other guys! I have done that too! You will like the smaller Chuck for all the small jobs you can't hold in a bigger Chuck. Make a new backing plate for that smaller chuck.

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    Quote Originally Posted by thermite View Post
    Not really about the OP's original post, but since you opened this......

    Quite happy with my Schunk "Rota-G" Thank you...
    No scroll here, but plenty accurate, and just gotta love them quick change jaws....

    YouTube

    Cheers Ross

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    Quote Originally Posted by AlfaGTA View Post
    Not really about the OP's original post, but since you opened this......

    Quite happy with my Schunk "Rota-G" Thank you...
    No scroll here, but plenty accurate, and just gotta love them quick change jaws....

    YouTube

    Cheers Ross
    Great product.. but... as I am NOT a "revenue shop"?

    I run a 2005 vintage all-aluminum Jaguar XJ8-L instead. I may have less money in that motorcar than what Schunk gets for their superb workholding goods, too!



    My better 4-jaws. Forged steel or at least "semi-steel"?

    SCA 7 + inch: (new, but VERY old stock.. Sweden, narrow jaws)

    Bison 6": (new, but VERY old stock.. Poland, narrow jaws)

    Yausa 6": (new, but VERY old stock.. Japan, HEAVY jaws)

    ISTR there is a vintage US-made Cushman-Skinner-Horton or such around on D1-3 integral-back as well.

    Bigger or smaller seldom-used are ignorant El Cheapo "San Ou". 4-J are just not as picky as scroll-operated, so they "work OK".

    I gave up buying "used" after about five attempts. Seems all the big kids got the good ones, then KEPT them.

    Most of what is in circulation, used, is wore out or has even been crashed. And that's for FOUR jaw!



    I'd not touch a used 3-jaw if even I allowed them under-roof at all. No fear. I do not!


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    Quote Originally Posted by louosten View Post
    Gentlemen;

    I'd like to buy, or make a spindle adapter to allow mounting of a smaller (and older) 3-Jaw chuck with a 1 1/2" x 8 thread to a larger spindle with a 2 1/4" x 8 thread. This may have already been done a million times (?), I just can't find the correct reference in the archives. The general concept I have is as depicted in this attachement:

    adapter.jpg

    If I have to make one, I'd like some advice on the following:

    1. General Configuration
    2. Material spec

    Intuition tells me it needs to be as short as possible, while still able to carry whatever load is applied. As always, thanks in advance for comments!

    Lou 0.
    A possible alternative approach: a 5C collet to chuck adapter. I have one that I use with a 4" chuck. This setup has been handy for lots of little jobs. Sorry, I can't help with sourcing; it came with a used lathe I bought and there are no names, numbers, or any identifiers on it.

    img_1336-2-.jpg

    Big_E


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