I've made a good number of small boxes and would now like to try my
hand at threaded boxes. What tool(s) should I buy? I note that neither
Craft Supplies nor Lee Valley list a threading tool in their catalogues
(the type I've seen used by John Berkley at shows.)

I'm in the uk and any advice/site pointers/etc. to get me started with
threaded boxes would be most welcome.

Thanks

Steve