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Help with worn tailstock

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rbertalotto

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#1
The bronze threaded insert on my Jet 1236BD lathe is stripped. I want to order a bronze nut to replace the worn part.

My lead screw measures either .558” Dia x 8. Or 14.2mm X 3mm threads apart.

It appears the leadscrew is metric ...14 X 3......correct?..
 

P. Waller

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#2
Possibly a square thread, if so it will be difficult to find an off the shelf part with such threads.

If a trapezoidal thread form, 30 Deg. ISO or 29 Deg. Acme it should prove less difficult. Make sure that you are not measuring a burr on the screw Major Diameter, .2 MM is a good deal over the nominal diameter which is always the maximum.
The thread dimensions may be found here https://mdmetric.com/tech/thddat16.htm
 

RJSakowski

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#3
.558" is only .0025" under a nominal 9/16". You should be able to determine whether the lead screw is metric or inch fairly easily. 8 tpi would be .125" pitch. You should have exactly 16 threads, not counting the first thread, in two inches. If the pitch is metric, 3mm, you will have 16.93 threads.

To make it easier to keep track,, I mark every fifth thread with a Sharpie.
 

benmychree

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#4
It should be easy enough to make a new one, using the screw to gage the new nut's threads.
 

whitmore

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#5
The bronze threaded insert on my Jet 1236BD lathe is stripped. I want to order a bronze nut to replace the worn part.

My lead screw measures either .558” Dia x 8. Or 14.2mm X 3mm threads apart.

It appears the leadscrew is metric ...14 X 3......correct?..
Maybe correct, but not complete; it's a LEFT HAND thread, isn't it? And, single start?

If at least some engagement is still possible, use a dial gage to find the advance with 1.00 turn of the handle,
that'll give you the best pitch measurement. 3mm and 3.175mm == 8tpi are the candidates.

In a pinch, ink the screw and press it against paper, it's easier than getting calipers to
read the sloped edges.
 

derf

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#6
Contact Jet....that's probably a standard common part.
 

rbertalotto

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#7
Thanks everyone! All great feedback. I'll measure again and then order a bronze nut to repair.
 

Richard King 2

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#10
how does the screw look?

You may have to make a new one of those too....

Good Luck
 
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