1236 lathe tail stock shear pin?

My Chinese 13x40 has a threaded hole coming up from the bottom of the tail stock casting and a hardened pin that fits the slot in the quill and is threaded at the bottom. It has a screwdriver slot for adjusting it. The pin is screwed in from the bottom until it bottoms out in the quill key slot, backed off just until it will slide freely the entire travel of the quill, and then a lock nut is tightened to the pin to hold the setting. It is a poor design. Its only redeeming quality is that it will probably fail before something more expensive does.
 
Most interesting that one can step drill all the way up to half inch with no pin of any kind in there. Bizarre.

-frank
 
I went the brass screw route, did pick up a couple of toilet bolts but they seem to have thin head to them.
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My Chinese 13x40 has a threaded hole coming up from the bottom of the tail stock casting and a hardened pin that fits the slot in the quill and is threaded at the bottom. It has a screwdriver slot for adjusting it. The pin is screwed in from the bottom until it bottoms out in the quill key slot, backed off just until it will slide freely the entire travel of the quill, and then a lock nut is tightened to the pin to hold the setting. It is a poor design. Its only redeeming quality is that it will probably fail before something more expensive does.

Is it difficult to get a wrench on the lock nut while holding the screw? Sounds similar to some valve lash adjusters on some four stroke motorcycles.
 
Is it difficult to get a wrench on the lock nut while holding the screw? Sounds similar to some valve lash adjusters on some four stroke motorcycles.
It is like a valve lash adjuster, but upside down, hex nut locking a screw with a screwdriver slot. In any event, it only is to stop rotation of the quill, so the adjustment is by no means critical, just get as much engagement as you can without bottoming in the groove and stopping or slowing the quill movement.
 
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