On 24/10/2019 18:10, Tim+ wrote:
John wrote:
lid (AnthonyL) wrote in news:5db09d2e.37820718
@news.eternal-september.org:

I've got a couple of awkward bleed screws. All the screws are direct
into the back of the radiator so not easy to get at and I've fractured
a couple of cheapo keys.

As a last resort I'd like to get a stronger key - what should I go
for? Draper Zinc?



With most keys it is better to file of the countersunk lead-in as this
wastes some of the gripping area and prevents you getting further onto the
square of the screw.

+1.

Ive never understood why so many of the brass keys in particular have the
socket countersunk (thus reducing the contact area).

Tim





I have never come across a bleed valve that goes all the way in until
the head is against the radiator. They normally have a pointy bit that
seals on the end and making contact with the head would stop them working.
Therefore a small chamfer makes bugger all difference to contact area
and does make them easier to make and use.