Main board Earth blocks - shear screws

[JohnW2]

Some of the gear the DNOs use works on the principle of tightening until it shears off, though in at least some cases the shearing part is a seperate cap that can be removed in the unlikely event it needs to be unscrewed.

That is certainly a practice employed in some walks of life - although, as I've said, not something I've ever heard of in relation to screws of electrical terminals - but I am certainly not au fait with most of what DNOs get up to.

The most annoying of all are the type of 'security screws' that sheer off, since they are deliberately designed to make it very difficult for anyone to get them out once they have sheared ( a bit like 'child-proof' things which are also 'proof' against many/most adults!)

Kind Regards, John

 

[JohnW2]

C'mon...which do you think?

I honestly don't know - which is why I asked the question!

Kind Regards, John

 

[frank999]

You will notice that what you thought was fully tight, now isn't
Spot on with that, a good few weeks later the degree of tightness feels uncomfortably wrong.

I had a thread running that discussed the notion of cable clamping with screw compression vs spring clamps such as Wago's.,

When stripping out old MK sockets from say 20 years ago - you notice that the cable clamping slot has a small metal plate in each point that acts like a vice ... with the screw behind pushing down, seems with most sockets today the end of the screw bears directly onto the wire, which bruises the copper, which always seems such a crude way to clamp a cable. Why did that change over the years ?

Today I witnessed a BG dimmer switches screws literally slice through 1.5mm² copper with very little effort - the screw couldn't be removed to inspect - but peering into the cable slot, the end of the screw was very crudely machined, and looked quite sharp, so as screw end rotated in contact with the wire, it cut like a knife - rubbish.

DNO's tapping into street mains - live, use shear bolts, then encase the connection in resin, ironically a case where they will never need re-tightening ... which brings us back to the use of Loktite.