M3.5

[altec]

Any 'practical tips' for what to do when a socket screw (M3.5) breaks in the flush mounting box and your left with a 'bit of screw' stuck in the box!

Also what do you call this:
it's like an M3.5 screw with the head cut off and a tapped M3.5 tapped hole in place of the head. I would imagine you would use it for extending out the 'holes' (on a flush box)which the screws normally fit but why would you want to do this?

 

[securespark]

Yes!

If your broken piece of screw has any length left to grip on, try unscrewing it using grips. If it is broken off close to the lug, you can try to drill it out - I use a 2mm drill bit (make sure it's sharp!), then rethread the hole. You can get an M3.5 rethreading tool from most wholesalers or RS sell one, too.

Sometimes if you are lucky (and the screw is broken off close to the lug) you can get pin nose pliers behind the lug and screw it out backwards (ie turn the screw clockwise from behind the lug), assuming there is enough screw to get a grip on.

When using the rethreading tool, take great care not to exert any sideways pressure when threading, as these tools can snap very easily under that kind of use and leave you with the same problem again!

If the lug you want to clear is the adjustable one, and it won't shift for love nor money, (I have done this) then you could buy the same brand of box and replace the lug by carefully prising up the metal tabs holding it in place, refitting the new lug and bending the tabs back down.

The "screw with head cut off" part you're thinking of is made by MK and called an extension stud (code 3710 ZIC). They are from memory about 35mm long. Basically, you screw these into the box lugs, and then the accessory fixing screws go into these. I used to see a lot of them, but these days, people tend just to use very long ordinary screws instead.

Hope this helps!