OK points taken and it seems that no damage was actually done but the arc was a bit intimidating.
The wedding ring seldom gets into exposed positions (fat fingers) but I am never without the trusty old (and thoroughly abused )Seiko Titanium, and the idea of it being welded to the chassis does not appeal.
However I am not sure if I can accommodate one of these https://www.cpaltd.net/dynamic-braki...l?options=cart

If I choose to dispense with the old Boxford control panel then that will vacate some space where the junction strip now resides so may think about it .
Laterally thinking, might it be possible to make the E stop a changeover switch which when it breaks connects the capacitor via the NO terminal to the heater to and thus on to earth , thus avoiding having an electric heater going continually in the panel as the machine is operating??