4mm alan head screws

[Adie moore]

in this image of an isolator the screws to tighten down on to the tails were 4mm alan heads. I wasn't happy at all, am I wrong? As far as I can see the main thing with am3 was to do with consumer unit fires which 9 times out of ten are due to bad connections.
with this isolator I don't know how much torque I could apply via a 4mm alan but it's not much and well less than a 6.5mm flat head screw driver. and I don't have insulated alan keys so my bum was twitching like a rabbit's nose.

edit; its a brand new meter and isolator.

 

[davesparks]

You can apply a lot more torque via an Allen key than you can a screwdriver.

Why was your bum twitching? Surely you were working on the dead side of the isolator?

 

[Adie moore]

it didn't feel like it. yes it was dead and proved dead, but still, at the back of your mind your thinking.....what if.

 

[davesparks]

it didn't feel like it. yes it was dead and proved dead, but still, at the back of your mind your thinking.....what if.

Just do the maths, it's a simple calculation of moments. With an Allen key you are applying the force to a lever a few inches long whereas with a screwdriver you are applying the force almost directly to the axis of movement.

do you not trust your own ability to work safely?

 

[Adie moore]

I appreciate your point and agree. however my concern was rounding out the head from too much torque. I'm sure they have been designed and tested and will function perfectly. I'd just rather something a bit more substantial.

just trying to keep it light hearted.

 

[Specialist]

DNO's have been using 4 & 5mm Allen head screws for lots of kit for years around here, Including overhead line taps etc. Never had a problem with not being able to torque them down properly.
If your going to be doing many & buying an insulated Allen key, the T keys are much better to use.

 

[Richard Burns]

The only nuisance with allen keys is they are not a post origin standard fastener so it is less likely someone has the right tool available, as demonstrated in your post.
If your torque screwdriver takes 1/4" bits then you can just use an allen key bit, though or course you are then limited to the same torque as for a screwdriver.
As Davesparks and Specialist have mentioned the torque that can be applied is greater than with a screwdriver and the standard tooling is the T keys. Though I only have insulated allen key screwdrivers because I am cheap.

 

[Pete999]

Get some Allen bits for your torque screwdriver body

 

[freddo]

Aren't these 3mm? The trouble with a lot of these hex type of terminals is the screw is substantially smaller than the terminal hole so if the conductor is shoved in and the screw tightened, most of the strands end up in the space either side of the terminal screws. What is really annoying is many of these isolators have proper, full sized terminal screws that are the same diameter as the terminal hole, with slotted heads on the DNO side.
Comparison of proper terminals and the new hex rubbish:

 

[Specialist]

Reichelt list a 4mm VDE insulated Allen T key for £4.98 + carriage.

 

[Midwest]

Without getting into the 'torque screwdriver debate' (although I think we will!), clearly it would be possible to overtighten these terminals more so then, than a typical screw head, which I guess is OP's point?

Do we have the manufacturers details, and their recommendations for torque settings?

My torque screwdriver (which by the way needs calibrating), does not accept Allen head attachments, so guess in this case, I would need to purchase another device to correctly torque such terminals.

Incidentally, last time I checked, the cost of calibration was almost the same of a new calibrated replacement

 

[Stufin135]

This was why Armeg launched their new torque screwdrive set last year with a 3mm and 4mm hex head bit. Not the cheapest set out there though.

Armeg SDSBSET001FL Fully Loaded VDE Adjustable Torque Screwdriver Set - Black/Red (13-Piece): Amazon.co.uk: DIY & Tools - https://www.amazon.co.uk/d/Screwdriver-Accessories/Armeg-SDSBSET001FL-Loaded-Adjustable-Screwdriver/B01IBPRI8M

 

[Midwest]

Those blades look a bit chunky, will they fit in the terminal recess of mcb's etc?

 

[sam400]

I've been fitting MCCBs today with Allen bolts think they were 16Nm!
Over 3 times what my torque screwdriver can manage.
you wouldn't get a PZ2 that tight without cam out

 

[Adie moore]

by the sounds of it I'm completely wrong then, which is actually reassuring. I don't have a torque measurement I was just going on feel. what size were the Allen heads that needed 16Nm?

 

[sam400]

I think it was 4mm key so M5 bolt, your get it pretty tight with a T bar.
A lot of those isolators only have PZ fasteners done up to 3nM so your prob fine.

 

[Resu]

Found an insulated Knipex T bar that a local DNO operative had dropped loading his van. Never saw him again so kept it. Best thing I ever found! We have quite a lot of those isolators up here and quite often the MET on the cutout (or Henley block) can be hex heads.

 

[Richard Burns]

I was informed by one UKPN operative that their guidance on tightening terminals was "as tight as possible" and since they were using the T hex keys that could be fairly tight, if 16Nm is the actual recommended torque perhaps this was not such a bad instruction as I originally thought.