Also of course, are you absolutely sure that the earth itself is real, IE is
the wire at the switch end and the supply end actually connected? You may
laugh, but screws have a habit of working loose and wires bent at right
angles in a short space can also break if quite old. I had an ally one break
to a cooker like this some years ago.
There has to be a reason as otherwise when the live shorted and the earth
on the box formed a circuit some protection somewhere would have tripped.
Brian

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"Harry Bloomfield" wrote in message
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PJK wrote on 24/06/2018 :
The bit I don't understand is why nothing tripped. The live and neutral
wires are both wired into the contactor and the earth from the lathe and
from the feed from the plug both connect to an earth terminal on the
switch casing and were done up tight. The socket in the garage is fed
from a dedicated 16 amp breaker in a modern MK consumer unit with an RCD.
Should that not have protected me?

The RCD will only trip, if sufficient current passes through you, to
earth. Possibly there was not a sufficiently low resistance path through
you to ground to trip it. Another possibility is that the RCD is faulty or
seized up. All are fitted with a test button, does it trip if that button
is pressed?