Back box lugs and cross threads.

[FatAlan]

Is it worth while re tapping lugs on back boxes? Just ordered a 3.5mm tapping tool as I had an issue at the weekend with the head of a screw shearing off and the resulting pain in the neck hassel of getting the remaining screw shaft out of the lug. This must be a very common problem. Is re tapping effective bearing in mind there isn't that much metal there in the first place?

 

[andyb]

I've always carried one, they're handy with poorly threaded lugs.

 

[kingeri]

If tapping out the lug is unsuccessful, you can also try drilling out the back of the box in line with the lug and use a long screw to reach right to the back. I have also managed to replace a lug before (obviously not a fixed one). I have also placed the threaded section from a drylining box behind the lug and managed to catch it with a screw and used that to secure the switch/socket. I found some of the older backbox screws my dad gave me are tighter in modern back boxes and seem to work without tapping.

 

[Andy78]

I use mine a lot more for tapping out poorly threaded new boxes than installed existing ones.

 

[Wonderwall]

It's certainly a handy tool to have. There is a fair amount of poorly threaded boxes on the market.

 

[Pat H]

On the odd time I have a duff thread I just use the junior hack saw to score the end of one of the screws alone the shaft. It makes a crude tap. Screw it in and it re-cuts the thread. Normally works.

 

[Rpa07]

In conclusion, when you haven't got one you wished you did and when you've got one it doesn't matter whether the thread is good or not - get me?

 

[FatAlan]

Thanks for tips chaps. It's silly snags like these that add time to a job.

 

[davesparks]

Yes these tools are worth having, I've got M3.5, M4 and an M20x1.5/M25x1.5 combined jobby, all very useful.

 

[FatAlan]

Recommend any particular sets / makes of taps?

 

[davesparks]

Recommend any particular sets / makes of taps?

I just use whatever my wholesaler has in stock, I use the threading tools that are basically a tap set in to a screwdriver handle rather than a full blown tap set.

 

[sparksburnout]

Useful to squeeze the lug with mole grips first, then re-tap. If you want to be nasty you can use a 3.5 nut and spring washer, nips up fine if you put a plug into the socket and pull it gently forwards as you tighten the screw. Guaranteed to drive the next person mad, specially under a kitchen cupboard.

 

[FatAlan]

Just ordered a CK type with screw driver type handle. Only about a fiver so will see if it's any good.

 

[Rpa07]

It will be

 

[FatAlan]

Last time I used taps and dies was aged 11 in metal work when making a screw driver. That was after the regulation key fob in metal which had followed the regulation laminated acrylic plastic key fob.