On 25/04/2019 19:50, Rob Morley wrote:
On Thu, 25 Apr 2019 05:27:35 -0700 (PDT)
wrote:

I was having some difficulty getting a good tight fitting of some
terminal strips and when I examined them I realised why.

http://wiki.diyfaq.org.uk/index.php/...nal-blocks.jpg

They have fractured with the force of tightening the screws on
conductors.

The metal block used to be solid brass (or nickel alloy?) in a
rectangular section, now it's extruded in that keyhole shape to save
metal and machining - I imagine if the extrusion isn't done at the right
speed/temperature or there are inclusions then that's the place it's
going to fail. I wonder if the screws are brassed steel these days,
rather than proper brass.

Good call. Also some brasses can suffer from stress corrosion cracking.
This might be "out of spec" brass.