When he tried to attach the new front cover it singed the screw and blew the fuse. What could be causing this?
I am still trying to get my head around how anything could singe a faceplate screw while you are still working on the open socket...??
As any competent person would only ever be working on circuits that have been isolated and proved to be safe and dead to work on..
So unless you actually mean "when you tried to switch the power back on after replacing the faceplate"... it tripped an MCB/RCD/RCBO.. It does rather suggest that the power had not been safely isolated?
Putting the live conductors into the Earth terminal on the faceplate...
and the Earth and/or Neutral conductors into any combination of Live and/or Neutral terminals.. (with earth fly-lead to back plate) would create some bangs/sparks/singes when front plate screws come into contact with back box...
BUT only if there is some rather dubious live working practices involved!!
As a side-note warning..
The key fundamental requirement for anyone trained competent and working with electricity on a daily basis is NOT to just get something working..
As any ***** can do that!
But it is to... Ensure ALL alterations AND additions will disconnect the supply fast enough in the event of a fault so as not to endanger anyone!!
I would be very cautious of shrugging off mistakes such as this as a "it will take a while to live down" sort of problem... As just because something appears to be working does not mean that it is safe...
AND.. as electricity cannot be seen, heard or smelt.. BUT it can kill a healthy adult in less than a second.. It is vital that ALL alterations / additions are tested correctly to prove the relevant protective devices can disconnect the supply fast enough so that no loved one's, family, or friends, could receive a fatal electric shock from some dubious DIY work!!
Lets just hope that there aren't other past DIY hazards lurking in your home that you are not aware of... e.g. accessories with NO earth connected and/or polarity reversed... these would not trip anything at the consumer unit... even though they are unsafe... But would appear to work OK!
Circuits extended with the wrong sized cross-sectional-area cable conductors.. e.g. adding extra sockets to a 32amp circuit with cables typically only good for 6amp lighting circuits
Would again appear to work OK!!
I Just hope that all the terminations are tight and ring continuity is intact if applicable!
And... I would still like to know if it was an MCB / RCD / RCBO that tripped???