Quote Originally Posted by Peter Laidlericon View Post
Or better still, bore into the existing thread. Now get a suitably threaded shaft, machine one end down to the diameter of the hole and soft solder* this new threaded shaft into the existing one. Cut to length. Now all you need to do is to machine a new thumbscrew head and thread that to the thread you've just inserted into the old lead screw. New locknut and you're home and dry. I did that to resurrect quite a few needy P-H sights at my sons old school (after being told many years before that they all needed to go back to P-H for repair by their expert craftsmen)
*soft solder means that you can always release it and start again. Unlike fixed-for-good compounds
Peter--

You gave me a better idea. I have access to a micro-laser welder and It can do the same as you suggested.

Many thanks

--fjruple