Hopefuldave
Cast Iron
- Joined
- Apr 1, 2010
- Location
- Surrey, England
I've discovered why my mill's motor comes straight on when power's connected, and why I can't stop the spindle motor or put the spindle into reverse...
Contacts on the forward contactor are welded closed (well, just one or two, the main motor contacts), enough to hold it in the "on" state and operate the aux contacts to prevent the reverse contactor pulling in (luckily...)
The contactors date from the early 60's, Italian, no maker's marks visible and unusually complicated with multiple aux contacts to enable / disable other functions like the feed motor, fed and spindle clutches etc. and fairly low profile (current available contactors with aux contacts would be poking out through the cast-aluminium cabinet cover...)
So... I'm looking at a major rewire, additional contactors to manage clutches etc., new cover if I change 'em out. Not good, and wouldn't look right!
I'm considering stripping the existing contactors and repairing instead, this will require separating the welded contacts, fitting new contact tips, so a few questions!
Separating - any method less destructive than a Dremelloid with the thinnest possible cutting disc? I've tried prying with the contacts in situ, no dice
Contacts / materials - silver/cadmium-oxide was the go-to until Europe came up with the COSHH regulations, would a silver/nickel or copper/nickel alloy be usable? Would I be better stripping a modern contactor or three and silver-soldering their points into the old relay? Could I even get away with building up new contacts with silver solder?
Any suggestions very welcome!
(Yes, it's always been like it since I got it, and no, I don't yet know why they welded closed...)
Dave H. (the other one)
Contacts on the forward contactor are welded closed (well, just one or two, the main motor contacts), enough to hold it in the "on" state and operate the aux contacts to prevent the reverse contactor pulling in (luckily...)
The contactors date from the early 60's, Italian, no maker's marks visible and unusually complicated with multiple aux contacts to enable / disable other functions like the feed motor, fed and spindle clutches etc. and fairly low profile (current available contactors with aux contacts would be poking out through the cast-aluminium cabinet cover...)
So... I'm looking at a major rewire, additional contactors to manage clutches etc., new cover if I change 'em out. Not good, and wouldn't look right!
I'm considering stripping the existing contactors and repairing instead, this will require separating the welded contacts, fitting new contact tips, so a few questions!
Separating - any method less destructive than a Dremelloid with the thinnest possible cutting disc? I've tried prying with the contacts in situ, no dice
Contacts / materials - silver/cadmium-oxide was the go-to until Europe came up with the COSHH regulations, would a silver/nickel or copper/nickel alloy be usable? Would I be better stripping a modern contactor or three and silver-soldering their points into the old relay? Could I even get away with building up new contacts with silver solder?
Any suggestions very welcome!
(Yes, it's always been like it since I got it, and no, I don't yet know why they welded closed...)
Dave H. (the other one)