I'm wood-butcher, not a tin-bender. I made an oak tool-tote 30 years ago. The wheels are from an old library ladder, and the chromed pipe handle extends to wheel it around the job site like a hand-truck. My son, a finish carpenter, uses it daily now.
I never even liked changing the extension springs. I saw the hole in the cement tile roof caused by the one that had broken. This was before they added the wire limiters. Now I hire it done; this is the only head I've got!
Ever try to remove a broken tap? They're harder than anything you might try to drill it with. My trick is to "freeze" it with a shot of CO2 and then shatter it with a hammer blow. It will usually fracture length-wise, and you can use a magnet to extract the shards.
How to manage the required force is the remaining question. Hard to duplicate his "the last time I went to 2 oclock and this time I will try 2:30"...
I think I'll ask a retired machinist friend to look at it.
"There are mechanics, and there are parts-changers."
What is the LRA on the label? That's the amp draw when starting. What's the amp rating of the circuit breaker, and what is the total load on that circuit?
I have a Desmond Stephan 500 vice I want to rebuild. I have disassembled it, and the main drive screw is bent! Can it be straightened, maybe by a machine shop? If not, where can I find a replacement?