Radiator key size query

[galaxi]

I'm trying to find a suitable bleed key for my radiators but am having difficulty finding the correct size.

The main square hole is half an inch across while the inner square 'valve' (ie the square 'rod' that needs to be turned) is about three sixteenths of an inch across.

Most keys I've found state they are for, for example, 1/2 inch, 3/4 in and 1 in valves. Are these stating the overall diameter of the key or the central cut-out that fits the inner square 'rod' ?

Sorry that the description uses some nosensical words - I'm not exactly up on radiator valve descriptions. :)

[The3rd Earl Of Derby]

Those old windup clock keys are the same size as the radiator bleed valves,

3/16th.

-- Sir Benjamin Middlethwaite

[galaxi]

Would that be the same as the key at the bottom of this page:

how about these:

most unhelpfully, doesn't say the size (unless it's assumed that they're all the same).

[Set Square]

I'm not sure what keys you've been looking at, but what you need is something like this:

working part is a 10mm (or thereabouts) rod with a 5mm square hole in it to fit the central pin of the bleed valve. Any decent hardware shop or PM will sell you one.

Some radiators have removeable bleed screw assemblies, where the whole thing screws into a boss on the end of the rad, and with the bleed pin in the middle. The assemblies have a thread on the outer diameter - typically 1/2" BSP (which is actually about 3/4" in diameter) - which is maybe where the reference to 1/2" etc. valves has come from - but they all have the same sized pin in the middle, as far as I know - and that's the only bit you need to worry about.

[The3rd Earl Of Derby]

The second and last brass keys are the correct type. The second url is also, but you will have to email about the size. I would say they are the correct size for radiator bleeding.

-- Sir Benjamin Middlethwaite

[Stuart]

Why do Screwfix describe it thus :--

Radiator Valve Key For loosening and tightening radiator valves

Why not just say it is a bleed key or something for bleeding radiators instead of what they say .

Stuart

[Mark]

That's helpful except clock keys run from < No- 1 to No- 25 A No 11 will fit a rad bleed valve, but the only one that measures 3/16 is a No 9 ;-(

-

[Dave Plowman (News)]

Have you actually bought one from B&Q etc? They're not exactly expensive and fit all bleed valves I've come across.

[galaxi]

I've got a multi-purpose one, it just doesn't fit two of my radiators.

Thanks to all for their help.