On turning off the lockshield valve on our living room radiator, I managed to shear off the top so needed to replace it. We have tried two new valves - an 8mm and a 10mm. The 10mm is too big and the existing nut won't fit over the thread, and the 8mm too small. Does anyone have any ideas what we need? The house was built in 1999 and has rear bleed radiators which require the smaller size rad key which we have already struggled to get. Can someone also tell me if a lockshield valve just refers to the type of cap fitted and not anything to do with the valve itself?
just remove the entire thing, drain down, remove rad valve and rad tail and fit shiny new one to fit your pipework...8mm,10mm or 15mm and then fill up. As for your bleed key, buy a tommy bar type off amazon or ebay....if they don't work then its a new radiator and time to call a heating engineer.
Post a piccky with something for reference a ruler or similar we can advise better then Yes lock shield and rad valves are the same inside just a different cap
Certainly looks like 10mm you may well need to remove the existing nut and olive from the pipe and fit the new ones also the tail piece that screws into the rad will need to be changed for the one from the new valve. http://www.screwfix.com/p/angled-radiator-valve-drain-off-10mm-x/36552 Try one of these, pretty sure they come with both type of heads. As said by Dubsie a Tommy bar rad key will reach around the back.
Thanks for all the advice. We have used a 10mm valve, just had to remove the old olive and nut and all seems to be well so far. Also got a Tommy bar rad key and that fits perfectly too! Great advice, thanks for your time.