4.8mm radiator key - help!

[LemonCake79]

I have a couple of very old radiators i need to bleed. I need a 4.8mm key, I believe this is 3 1/6th's of an inch in imperial. Google suggests it may also be called a 'size 12 clock key'.

I've been replacing the radiators as I've decorated hence there only being a few old ones left. The fittings are too worn to use s thing other than a proper bleed key but I can't find one anywhere.

Google comes up with loads but when you look more closely and read the information they are the more modern 5mm one. Sometimes they even say 4.8 but there will be bad reviews from people who've bought them to find they are 5mm.

Getting desperate... does anyone know if they still exist and where I might buy one please?

eBay?

Can you post a picture of the valve

www.amazon.co.uk/BRASS-CLOCK-SPIDER-WINDING-KEYS/dp/B017RP1T6O?tag=mumsnetforu03-21

clock key size 10

www.ebay.co.uk/itm/281157808905

@PigletJohn you absolute legend. I shall think of you when I'm all toasty in my little study now.

I'm not sure I've been using the right search terms as I had tried Amazon. All ordered 

@SweetBabyCheeses99, did try eBay but had the same issue with something looking promising but the reviews saying it didn't fit.

@Em45634, no, I hadn't tried that. Good idea, thank you.

@dementedpixie, think I'm sorted but thank you so much for offering to look.

I have very old radiators with a Recessed bleed nut. Apparently I need an
imperial vent key. Lemoncake where did you get yours? Seems all on amazon are the same!

Anyone? Its not reachable with a regular key.

Show us a photo. I expect it is a normal square. If you are fond of simple plumbing you can probably fit a new plug.

so the nut is recessed - usual key i use on other rads doesnt reach it, so dont know if it would even fit, and its also worn into a circle on the top.
thanks

There is an octagonal shape that a spanner would fit. Is it an octagonal projection, or an octagonal hollow? Or both? Take a diagonal photo as well please.

Take a photo of the other end too please.

Radiators are made with round threaded holes on ( usually) all four corners, and plugs, vents or valve tails are screwed into them. Older ones are undone with an L shaped key, newer ones with a spanner. Newer ones are sealed in place with PTFE tape, which prevents leaks and seizing of the thread. Old ones were sealed with plumbers jointing compound that sets very hard and sometimes the threads rust together. Scrape away the excess compound to see it better. The plugs are always removable, but sometimes very difficult if old and seized. A wrinkly old plumber can usually do it. The size and thread of the plug has not changed for a hundred years.

If that one is too difficult, you can remove the plug at the other end and fit a new vent.

Here is an example of a modern vent and plug, fitted using a spanner. They are very cheap and easy to fit. If you ending up getting a plumber, or managjng to do it yourself, I'd change them all to save future problems. You don't need to drain the system, just turn off the valves at each end of the radiator (and afterwards, open exactly the same amount they were at before).

https://www.screwfix.com/p/radiator-vent-blanking-plug-nickel-2-pack/40972

You wind a few turns of the tape onto the thread, clockwise, cut it off with sharp scissors, and run your finger round to press it into the grooves. Its thickness is practically nothing so it should not rub off or pucker up when you screw it in.

https://www.screwfix.com/p/ptfe-tape-for-pipe-joints-12m-x-12mm-10-pack/4625x

If it is 4.8mm across the nut I would think a 5mm nut spinner would do it.

You might need to pad it slightly.

4.8mm is ³/₁₆inch