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.

 

[Rpa07]

Everyone remembers their first knurled screwdriver handle!

 

[FatAlan]

Had to laugh the other day when my son came home from school with his laminated plastic key ring. Some things never change!

 

[Dave OCD]

The M3.5 tap is also useful when plasterers of today fill up the lugs with cr@p, as well as a fair bit of the box. There was a time when they cleaned boxes out really well but that seems a rarity these days.

 

[VoltzElectrical]

I carry M3.5 and M4, and yes they are invaluable. As mentioned, if the screw 'pops', then compress the lug slightly then re-tap. At the moment I am retrofitting bollards in a caravan park whereby I remove the top half of the attaching plate, leaving the bottom half of the plate attached to the part in the ground. This leaves me with an 8" flat plate with the cable coming through, which I then drill and tap to accept M10 bolts for the new bollard. Oh, and did I mention it was raining.

To make matters worse, the old cables were terminated into 4" metal boxes that don't fit into the new bollards so i also have to grind these off before reglanding the SWA into galv U-boxes with a flex outlet.

Oh, and did I mention it was raining?

 

[telectrix]

so you got wet. think anyone cares? i don't .