Strong headed screws

Ectophile

Make sure you're using the right screwdriver for the job.  Flat screwdrivers need to have a nice flat end, but they tend to round off with age.  Use the biggest one that will fit the screw head.

Pozidrive is not Philips.  The screwdrivers have different shaped ends.  They may appear to fit, but will "cam out" a lot easier than they should.

fenwick458

not uncommon to me. firstly any M3.5 socket screw will be made of a soft metal, they are designed to be cut easily so are made of a soft metal, and they are made very cheaply so you can expect varying tolerances
2, some brands are worse than others, at worst you could end up with an MK or Chinese plate screw which will require a 3.5 tap/re-threader to be run through the backbox lug before you even attempt to put your new plate screw in. failing to do this will result in stripping the thread or cross threading it and damaging the lug on the backbox.
at best they are still not brilliant, as a rule of thumb if you can't start it with your fingers or minimal force using a screwdriver then use the re-threader tool first
3.I'm assuming the thread stripping is actually to the threads, but if the problem is the head is becoming chewed off then use a bigger screwdriver, and apply as much pressure towards the screw as you can whilst turning anti clockwise.

i've sometimes been to jobs where every single plate screw is almost impossible to remove, and most of the time it will result in total stripping and having to cut something off, and I used to think this has to be down to the installer using an impact driver to fit them, or just being carless whilst fitting them. but, over the years have in fact re-visited jobs that I did many years ago and found them to be very difficult to remove, yet I know they were installed properly.....
I'd say sometimes this was due to environmental factors, i.e damp, corrosion, but that's obvious to spot, sometime I drag a screw out of a backbox that I know I put in fine, yet it doesn't want to come out and results in total destruction of either the screw or the backbox...!
So I think the bottom line is,

1. M3.5 machine screws produced very cheaply en-mass, 
2. plus mass produced M3.5 plate screws, all produced to a price point 
3. both of them made out of a soft metal, 
4. both of them a very fine pitch,
5. sometimes the switch of socket is slightly off centre, so the thread will start ok but as it goes in at a slight angle it will get harder
6.  it's no surprise it goes wrong sometimes

A tip I have for anyone removing or re-fitting electrical switches or sockets, but a re-threader tool, and buy some extra screws. they will both cost less than £10 so it's hardly unreasonable. also if a screw is not biting, simply use a pair of snips to squish the backbox lug so that its slightly oval, then rethread it and it should work fine

neilmcl

Le_Kirk said:

nofoollikeold said:

The screws for electrical boxes are usually made of brass, which is soft.  
Check that the screw holes in the back box are clear.  They often get blocked with plaster.  If you have run, run a 3.5 mm tap through the screw holes, otherwise use a screw to clear the threads.  
By flex I assume you mean cable.  Back boxes shouldn't have any flexible wires in them.  

I would agree with the comment but when/if you go to buy a tool such as above, don't go to an electrical wholesalers and ask for a tap, they will send you to the plumbing store next door.  Being an engineer I asked for a tap, only to get the stock answer and was told the proper word is a re-threader!

If I go to my local hardware store that's been running for nearly a 100 years and ask for a 3.5mm tap kit, they'd know exactly what I was after. Not sure what wholesalers you go to but they sound a bit rubbish. 

coffeehound

I've heard of them called 'thread cleaners' too.  They aren't used to create a thread from scratch so it's reasoonable to not call them taps and dies I suppose.

Le_Kirk

Ganga said:

Le_Kirk said:

nofoollikeold said:

The screws for electrical boxes are usually made of brass, which is soft.  
Check that the screw holes in the back box are clear.  They often get blocked with plaster.  If you have run, run a 3.5 mm tap through the screw holes, otherwise use a screw to clear the threads.  
By flex I assume you mean cable.  Back boxes shouldn't have any flexible wires in them.  

I would agree with the comment but when/if you go to buy a tool such as above, don't go to an electrical wholesalers and ask for a tap, they will send you to the plumbing store next door.  Being an engineer I asked for a tap, only to get the stock answer and was told the proper word is a re-threader!

Never heard them called that ,i worked in engineering for over 50 years and they were always taps and dies .

Neither has I until I tried to buy a 3.5 mm tap from them and I worked in engineering for a similar length of time!

neilmcl said:

Le_Kirk said:

nofoollikeold said:

The screws for electrical boxes are usually made of brass, which is soft.  
Check that the screw holes in the back box are clear.  They often get blocked with plaster.  If you have run, run a 3.5 mm tap through the screw holes, otherwise use a screw to clear the threads.  
By flex I assume you mean cable.  Back boxes shouldn't have any flexible wires in them.  

I would agree with the comment but when/if you go to buy a tool such as above, don't go to an electrical wholesalers and ask for a tap, they will send you to the plumbing store next door.  Being an engineer I asked for a tap, only to get the stock answer and was told the proper word is a re-threader!

If I go to my local hardware store that's been running for nearly a 100 years and ask for a 3.5mm tap kit, they'd know exactly what I was after. Not sure what wholesalers you go to but they sound a bit rubbish. 

It was one we had used locally for work, Newey & Eyre - similar to City Electrical Factors.