[How-To] Threading a chuck backplate

Jim F

Jim F

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The new to me 3 jaw chuck does not fit my spindle.
It is 1 1/2-8, as is mine.
It starts but tightens up about 1 thread on.
The backplate threads are flat on top, I think they are not deep enough for my spindle. So, when I put it in the 4 jaw, where do I indicate it?
Spindle register or chuck register ?
 
Hey Jim ! I'm amazed at all the threads on here stating the back plates and chucks not fitting spindles , not running true etc . Are these manufacturers not using thread plug gages anymore ? As to your question , I would think the spindle register is more important , but I would true up both if it were me .
 
mmcmdl said:
Hey Jim ! I'm amazed at all the threads on here stating the back plates and chucks not fitting spindles , not running true etc . Are these manufacturers not using thread plug gages anymore ? As to your question , I would think the chuck register is more important , but I would true up both if it were me .
Click to expand...
This is an old Horton, came from an Atlas owner on here.
 
If it fit his , it should fit yours ! Did you check YOUR spindle threads ?
 
Yes, my spindle threads are almost to a point, the chuck threads are flat on the top, almost like acme, but they are 60 deg.
All of my chucks and plates have almost sharp threads.
It's like the threads are not cut deep enough.
 
The flat is irrelevent . The pitch diameter is what matters .
 
I'll look for a tap . Could be the internal threads are damaged on the backplate . I would run a tap thru it before machining it . You may end up with a paperweight .
 
Don't use the chuck mounting surfaces. Once you get the back plate to to fit your spindle you will have cut whatever it takes off of these to true the backplate to YOUR lathe. This is another reason that lathes are so good at what they do. I would flip it around and use the thru hole.
 
A tap would be pretty awesome! You will still ha e to cut the face and edge afterwards.
 
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