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Old 11th Apr 2018, 9:25 pm   #1
gramophone1
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Default MK Safety Plugs

Hi. I am new to this forum.

I recently purchased some new MK Plugs, and I have to say they are not the quality I was expecting.

The Vintage MK Safety Plugs were much better quality. I have found with the new plugs, you can't tighten down the caps that hold the wire too tightly, because the bolt you screw the cap on to snaps if over tightened.

You can only go about finger tight.

It goes to show that most vintage plugs, fuses, etc were usually superior in quality.

Has anyone else experienced this ?
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Old 11th Apr 2018, 9:45 pm   #2
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Default Re: MK Safety Plugs

I've experienced this with MK switches and sockets. Not the quality terminals of the past.
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Old 12th Apr 2018, 12:01 am   #3
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Default Re: MK Safety Plugs

I noticed this a few years back- originally, they had closely-toleranced brass knurled nuts that could be done up encouragingly tight but they changed to floppier ones that seemed to be of something softer (zinc alloy?) that strip all too easily. Not bought any for a few years, perhaps lower-quality brittle studding is another subsequent "improvement"?
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Old 12th Apr 2018, 12:14 am   #4
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Default Re: MK Safety Plugs

Seems that MK manufacture is being progressively shifted to the Far East. I have commented in another post about the lamentably poor design of the windows for, and mounting of, the neons of their cooker point with 13A socket.
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Old 12th Apr 2018, 2:02 am   #5
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Default Re: MK Safety Plugs

Probably cost cutting due to the competition from that ghastly BG crap that seems to be the default go-to for every electrician who isn't too concerned if the light switches are still working a week later. The Council did a one-day rewire of my flat a few years ago and 3 of the switches didn't even make it as far as inspection and testing. Seriously.
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Old 12th Apr 2018, 3:09 am   #6
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Default Re: MK Safety Plugs

I was PR Officer at Crabtree in the early 90s when together with MK the quality of the products from both companies was irrefutably market leading. I wrote press releases and articles on how far eastern products although somehow able to achieve the standards required on paper, were more often than not inferior, or even dangerous. I had a morbid collection of photos showing burnt and exploded examples of plug tops and sockets. The market was very dependent on the specifiers sector, and with individuals' retirements as old boy networks gradually shrank (for better or for worse), electric wiring accessories became commodity products, and thus began the race for lowest prices, poor qua!ity overseas sourcing, and no-one seemed to care so long as the stuff 'was seen to be legal' and fit for purpose according to its paperwork. Well, like I say, we all knew that it was often poor quality and lobbied accordingly, but if the goods achieved the required British Standards, there was little else we could do. And sadly that's were we are now, a plethora of poor quality wiring accessories flooding the market under a myriad of brand names, made in the far east. I'm not sure if Crabtree still manufacture in the UK, I will check.
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Old 12th Apr 2018, 4:12 pm   #7
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Default Re: MK Safety Plugs

Given the price (I bought a few at once) the cheapest being about £3.50 per plug ! They are just not worth the money.

I makes me wonder if these plugs are even safe if you can only go finger tight. They will work loose over time.

I have some vintage Marbo plugs, which are all top quality brass parts. I will go back to those I think.

It is so frustrating buying what I thought would be superior quality plugs, only for the MK's to come up far short on quality. I don't like the plastic cord grip either. The screw down cord grip is much better.

Disappointing.
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Old 13th Apr 2018, 12:50 am   #8
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Default Re: MK Safety Plugs

Funnily enough, today (Thursday) I bought a 2 gang MK grid switch (apparently the only way to get two 20A switches that fit a single box). Plastic front plate and switches made in UK, Grid plate made in China. Quality seemed OK until I tried the two M3 screws (supplied with the front plate) that attach the front plate to the grid. They were evidently out of tolerance as they would fit neither the grid plate nor ordinary M3 nuts. I had to run them though an M3 die first, which required non-trivial force. Never had this sort of problem before.

Last edited by emeritus; 13th Apr 2018 at 1:03 am.
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Old 13th Apr 2018, 1:51 am   #9
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Default Re: MK Safety Plugs

Quote:
Originally Posted by emeritus View Post
I tried the two M3 screws (supplied with the front plate) that attach the front plate to the grid. They were evidently out of tolerance as they would fit neither the grid plate nor ordinary M3 nuts. I had to run them though an M3 die first, which required non-trivial force. Never had this sort of problem before.
All the ones I have found have been M3.5?
When I made a custom back plate I had to use an M3.5 tap for the holes.
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Old 13th Apr 2018, 9:06 am   #10
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Default Re: MK Safety Plugs

I agree with Refugee - M3.5 each time!

Presumably older ones were 4BA (3.6mm) but I've never had to question these.
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Old 13th Apr 2018, 9:40 am   #11
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Default Re: MK Safety Plugs

Yes. M3.5. I save all the old M3.5 fasteners I find for use with electrical fittings.
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Old 13th Apr 2018, 11:04 am   #12
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Default Re: MK Safety Plugs

Must be a design change. The faceplate screws are definitely M3. Photos showing one of the short M3 screws that came with the plastic faceplate against the usual M3.5 electrical screw for comparison attached. The cheesehead captive screws attached to the grid plate for screwing to a standard box are M3.5.
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Old 13th Apr 2018, 12:24 pm   #13
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Default Re: MK Safety Plugs

I have found a quicker way of dealing with missing 3.5mm screws.
I clicked on a buy it now button and got a bag of them for a about a quid.
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Old 13th Apr 2018, 4:20 pm   #14
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Default Re: MK Safety Plugs

I believe the older back boxes did take an 4BA screw (whereas now it is certainly M3.5).

Screwfix sell M3.5 screws (they class them under 'electrical screws' on the website) which can be useful if you need some in a hurry. Doubtless other similar companies sell them too.

I have an M3.5 tap and die. Not just for cleaning up the threads on electrical back boxes, but also because that is the thread on HPIB cable jackscrews. Well, OK, early HPIB cables were 6-32 UNC, but most are M3.5
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Old 13th Apr 2018, 4:23 pm   #15
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Default Re: MK Safety Plugs

Incidentally, related to screw threads _and_ MK plugs, the thread for the terminal nut changed at some point. I lost a terminal nut from a modern plug, and one from my spares box (I keep such parts from plugs that have cracked plastic parts, etc) did not fit. I am not sure what the 2 threads are, possibly again 4BA and M3.5.

If modern MK plugs are not much good, what _currently made_ plugs are recomended by people here? I still have a few old MK ones in stock, but I am going to run out sometime.
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Old 13th Apr 2018, 4:32 pm   #16
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Default Re: MK Safety Plugs

Quote:
Originally Posted by emeritus View Post
Must be a design change. The faceplate screws are definitely M3. Photos showing one of the short M3 screws that came with the plastic faceplate against the usual M3.5 electrical screw for comparison attached. The cheesehead captive screws attached to the grid plate for screwing to a standard box are M3.5.
Yes, you are absolutely right! MK ‘grid’ faceplates have used M3 screws to fasten the faceplate onto the grid yolk for many, many years. Standard M3.5 screws fasten the yolk to the back box. Nothing has changed here!
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Old 13th Apr 2018, 5:19 pm   #17
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Default Re: MK Safety Plugs

What about the MK tough plug ?

They seem good quality. The ones I used were fairly easy to wire.

Very plastic though.

I have never used a vintage tough plug, so I can't compare quality.
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Old 13th Apr 2018, 9:45 pm   #18
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Default Re: MK Safety Plugs

Do they need the lid slid down the flex before you start wiring up?

A lot of plugs like that have a slash in the rubber where someone forgot & didn't want to redo it all.

I have an RS branded plug that has a gap in the plastic to stop this happening.
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Old 13th Apr 2018, 10:25 pm   #19
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Default Re: MK Safety Plugs

Quote:
I'm not sure if Crabtree still manufacture in the UK, I will check
Crabtree, or Siemens Electrium as they are now, have been making stuff in China for a fair few years now. My new boxes of Capital switches and sockets have 'made in China' moulded into them. Old stock has 'Made in England' in the same place.

I've never had any serious problems with MK plugs except for an article I read a fair few years back about a recall of some sort.
The thing about the terminal posts is that they grip really well with minimum torque required which risks crushing the flex strands.
I did have one with a badly tapped screw but a bit of grease stopped it squeaking.
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Old 14th Apr 2018, 9:06 pm   #20
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Default Re: MK Safety Plugs

Quote:
Originally Posted by TonyDuell View Post
Incidentally, related to screw threads _and_ MK plugs, the thread for the terminal nut changed at some point. I lost a terminal nut from a modern plug, and one from my spares box (I keep such parts from plugs that have cracked plastic parts, etc) did not fit. I am not sure what the 2 threads are, possibly again 4BA and M3.5.
I have the same experience, and have just checked in my box of spares.
One type is certainly M3.5.
I would be interested to know what the other is - having just ascertained that it is not 4BA, M3, M3.5, nor 6-32UNC. I wonder if they are 5BA (often used in GPO equipment), but I can't find a suitable screw to check.
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