Hi Barry,
Thank you for the links.
The lead screw is one of (or similar to) those:
http://www.ebay.com.au/itm/TRPZ10x2-...0AAMXQVgBRGidh
During my first year at uni, we were required to spend couple of days in workshop (I worked on lathe and was very good at that)... I remember they used the "bath" of molten (red hot) salts mix for hardening the lower carbon-content steel, not sure what was used...
I also made my own hammer then (500g), that I used later for many years.