[How-To] Threading a chuck backplate

Jim F said:
I just checked and I do have an internal threading tool that will work.
Now if we have the 43 high temp. they are calling for, I might be able get to it tomorrow.
Click to expand...
Wuzzy ........................it's colder than that here in my shop at work . :rolleyes:
 
OK, gotta admit I didn't read the entire thread, but I had your exact same issue on my lathe two years ago. Swore up and down that the thread was undersized and even went so far as to make a lap to bring the thread larger. But I was wrong.

Just behind the spindle thread is a ground cylindrical register surface. Most faceplates will come undersized to this register, will start to thread on and then stop. You must machine the non threaded ID on the back of the backplate to fit to this register. It is super easy to miss if you aren't aware.

If you need to check your thread ID, buy yourself some thread wires and practice making GO NOGO gages for that thread. You can easily tell if the backplate is acceptably sized using these shop made gages.
 
macardoso said:
OK, gotta admit I didn't read the entire thread, but I had your exact same issue on my lathe two years ago. Swore up and down that the thread was undersized and even went so far as to make a lap to bring the thread larger. But I was wrong.

Just behind the spindle thread is a ground cylindrical register surface. Most faceplates will come undersized to this register, will start to thread on and then stop. You must machine the non threaded ID on the back of the backplate to fit to this register. It is super easy to miss if you aren't aware.

If you need to check your thread ID, buy yourself some thread wires and practice making GO NOGO gages for that thread. You can easily tell if the backplate is acceptably sized using these shop made gages.
Click to expand...
I did measure the spindle register,the new chuck is 1.5, my spindle is 1.510. I think it might be a combination of the 2.
The new chuck only goes on maybe 1 thread then locks up.
This a new to me chuck. It is a Horton, I believe it is 30's or 40's vintage.
 
Jim F said:
I did measure the spindle register,the new chuck is 1.5, my spindle is 1.510. I think it might be a combination of the 2.
Click to expand...

So the spindle register is larger than the bore? If so, that's the issue.
 
Jim F said:
I did measure the spindle register,the new chuck is 1.5, my spindle is 1.510.
Click to expand...
Huh ? .010 interference ? Are you even making it down to where the backplate registers onto your spindle ? You need to take some measurements , write them down and post them on here . If your spindle is 1.510 , you're gonna need a thou or 2 over that on the backplate . This ain't rocket science . :grin:
 
mmcmdl said:
Huh ? .010 interference ? Are you even making it down to where the backplate registers onto your spindle ? You need to take some measurements , write them down and post them on here . If your spindle is 1.510 , you're gonna need a thou or 2 over that on the backplate . This ain't rocket science . :grin:
Click to expand...
No, it is only going on maybe 1 thread.
I checked the register to see if it was going to fit.
 
Measure your spindle register , whatcha got ?
 
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