Repairing back box lugs

[jabuzzard]

Has anyone tried using something like these (3.5mm clinch nuts) for repairing back boxes where the thread on the lugs is damaged?

http://appianfasteners.com/pem-cls-m3-5-0-m3-5-clinch-nut-stainless-bag-of-100.html

In theory one would just need to drill out the hole to 4.75mm insert clinch nut and job is a good one. What do you think?

 

[EFLImpudence]

Could you drill a nearly 5mm. hole in the lug?

It would seem easier to re-tap it.

 

[securespark]

You could get one of these and glue it in place with araldite:

http://www.amazon.co.uk/3-5MM-SOCKET-SWITCH-SCREW-EXTENSION/dp/B007T8RTL4/ref=pd_cp_60_1?ie=UTF8&refRID=0XEXWA0N7V9DYMT90NSV&dpID=21ytTN8DchL&dpSrc=sims&preST=_AC_UL70_SR70,70_

What I have also done in the past is tapped with 4mm and put a CSK M4 in.

 

[jabuzzard]

Could you drill a nearly 5mm. hole in the lug?

It would seem easier to re-tap it.

Often re-tapping does not work, and yes there is never going to be a problem with a 4.75mm hole in the lug because the existing hole is at it widest 3.5mm so an extra 1.25mm is nothing.

I just thought this was a more professional and better solution (aka not a bodge) than gluing stud extensions or using none standard size screws. Would work out at around 10p per lug fixed.

 

[JohnD]

how does the clinch nut secure itself to the lug?

 

[stillp]

Would there be enough metal around the insert to hold it securely?

 

[ban-all-sheds]

there is never going to be a problem with a 4.75mm hole in the lug because the existing hole is at it widest 3.5mm so an extra 1.25mm is nothing.

Unless the lug is no more than 4.75mm across at its narrowest, in which case nothing is what you'll have left. Then, of course, there's the fact that the specs for it say you need a minimum of 11.2mm dia for the material...

 

[ban-all-sheds]

Would there be enough metal around the insert to hold it securely?

I'm guessing not...

 

[rsgaz]

I have read before, probably on this forum, of someone drilling through the back of the box with a 2.9mm HSS drill and then tapping the rear of the box to take an extra long plate screw. This method would damage the HSS drill and then damage the tap as it hit the brickwork behind (fine for a metal box on a wooden batten in a stud wall though of course).

If changing the box was too difficult or going to make too much mess and the lugs were already too damaged for re-threading, you'd be better off drilling through the lugs and then through the back of the box with a 5mm HSS bit, switch to a 5mm SDS bit and drill out deeper. By keeping the lug in place initially, it should help you drill the back of the box in exactly the right place. Then bend/snap the lugs off out of the way and just screw one of these.....

http://www.amazon.co.uk/3-5MM-SOCKET-SWITCH-SCREW-EXTENSION/dp/B007T8RTL4/ref=pd_cp_60_1?ie=UTF8&refRID=0XEXWA0N7V9DYMT90NSV&dpID=21ytTN8DchL&dpSrc=sims&preST=_AC_UL70_SR70,70_

...into a yellow wall plug in the back of the box.

Gaz

 

[Iggifer]

I have read before, probably on this forum, of someone drilling through the back of the box with a 2.9mm HSS drill and then tapping the rear of the box to take an extra long plate screw. This method would damage the HSS drill and then damage the tap as it hit the brickwork behind (fine for a metal box on a wooden batten in a stud wall though of course).

I've done this a few times to be fair. I use a 3mm HSS bit, and never had any issues with it. You could damage the bit of course, but you can pick up 3mm HSS bits for pence, and there are so few boxes that are actually flush to the blockwork on all parts of the box, not really an issue. And as for your threader, you've already cleared most of the space behind it with the HSS if there is block in the way.

I've also used this technique with a 3.5mm HSS and 4mm rethreader to replace broken off backbox earth lugs.

 

[ban-all-sheds]

Plus if the thread is shot you might get away with nipping the lug with pliers.

 

[Iggifer]

Plus if the thread is shot you might get away with nipping the lug with pliers.

Yea that's obviously first port of call, it's when the fixed lug snaps off you're up the brown creek

 

[ban-all-sheds]

Aye

 

[kai]

I have encountered broken lug problems on a couple of back boxes in my house - they are all dryline boxes though, so I bought a similar box and swapped out the lugs with the new ones, and problem solved. (They were the commonly available Appleby type boxes with the yellow plastic screw lugs on their sides). Saves disturbing the tiling around the box edges.

 

[333rocky333]

I have an AVK clinchnut tool and the smallest clinchnuts ive used are 4mm however the tool that fits them needs about another 6mm clearance round the nut, I use 4, 5 and 6mm quite often.
They dont do 3.5 mm but do a 3mm I was tempted to try 3mm ones and see if they rethread to 3.5 but as yet not found a seller.
As well as buying the tool you also need a mandrell for the size your using.