stuck radiator bleed screw

[Willam]

There is air at the top of our old radiator( probably fifty years old) in the first floor bedroom. Unfortunately the radiator bleed screw is stuck and does not respond to the small T type radiator key.
If I use pliers on the radiator key to apply extra leverage to try loosen the bleed screw, is it likely to strip the thread and cause a water leak?
Would appreciate any advice.
Thanks

 

[WC1]

Unlikely. Scratch off as much paint etc as possible around the bleed with a fine point.

 

[gmartine]

Your more likely to bend or break the key before you strip the thread, if it's a struggle and the rest of your rads are similar try investing in a set of larger set of radiator spanners that will allow more leverage.