Sb 13 Chuck replacement

SDE 56

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I need to replace the old Union Mfg Co. chuck on my SB 13. I have another 6" chuck on hand. It would attach to the old backing plate after I drill three thru holes in the backing plate on what I believe to be a 5.592" bolt circle. I have not measured it yet. This Chinese chuck has a recessed step in it about 3/16" deep. Do I need to adapt the backing plate so that it has a step in it to accurately locate the chuck and to provide rigidity or will the three M8 bolts have enough strength to hold it securely?
TY
SDE
 
The step is for the register between chuck and backplate. This will determine the runout of the chuck so you want these surfaces to be as accurate as possible.

The challenge is you need a lathe to machine the surfaces to match.

The M8 bolts are to hold the chuck and backing plate and should be strong enough, but are not the register.
 
I would add that the register diameters on the backplate and the chuck need to be nearly dead nuts the same exact size
 
These guys have given great advice. I suggest to all SB owners to find a copy of this book (it's available for free downloads). Just remove the old chuck, following the instructions from the book, clean everything and mount the backing plate on your spindle. Since yours has been machined previously, I would still take a very, very light true up pass on the face where it mates to the chuck and probably make a minimal register length since I don't know how much material you have left from the previous machining. Leave the plate as thick as possible while still facing true and turning the new register diameter.

Right out of South Bend's "How to Run a Lathe".

Ted

SB Mounting Chuck.jpg
 
If you turn the back plate on the same lathe that it will be used on it should be quite accurate and not difficult to do. If you are feeling cautious you can "creep up" on the final dimension, back off the lathe tool, and use the chuck to check the fit. Make sure there are no burrs on the back of the chuck.

I did that and I'm just a regular hobbyist. After I got the the back plate to fit, I then just clamped the chuck to the back plate, used a transfer punch, and drilled and tapped the holes.

https://www.hobby-machinist.com/thr...in-your-shop-today.14637/page-265#post-416421
 
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