Broken worms seem to be quite a common issue

For easy removal of a stuck chuck use a block of wood, engage backgear and rotate the belt spindle manually in a backwards direction

I'm lucky because my Drummond has a handy grubscrew hole in the v-belt drive and I can put a thin bar into it to use for extra leverage

Welding cracked corners works well but you need to be in practice and have a steady hand. I found a cheapy mini diamond file set (freebee with an order from ArcEurotrade) very useful for cleaning up. Especially inside the square. But the ones I fixed were very badly mullered. On one I had to cut the remains of a key hole side completely off and weld a replacement side on so getting weld inside was almost inevitable.

If stick welding a half decent inverter welder is a lot better than the old style buzz box for this sort of precise, low current, work as you can use rather lower settings and still get a clean weld. Flip side is the need to be much more positive when breaking the arc. My Fronius brand magic box will stretch the arc to 6 inches or more, even on quite low currents, if you are not decisive enough on the break. Allegedly the industrial rated inverters are much better performers than the low end DIY breed. Before using mine a practised welder friend claimed inverter welders were grossly overrated and no better then a basic buzz box. I had to be quite firm when ensuring that the welder stayed at home in my workshop!

Clive