interested in buying the bleed-off valve for an old (about 60 years old hot water heat radiator), the treaded stem is abot 3/16 of an inch wide..

Have you tried to bleed the radiator it may be full of air.

if it has a thermostic valve (number should be visible and gives an indcation as to the flowrate thro'this rad.) check to see if the pipe just below this is warm/hot, if so in all probability the valve has become gummed-up or a piece of grit has blocked the hole were the valve needle is Aremove valve (easy) or rotate the valve from the low to high settingseveraltime, until it feels loose, then set to the hottest position, OR tap the metal part of valve fitting with the end of a spanner, you can normally WHACK IT BUT NOT WITH A HAMMER!! B of B JIMZJAZZ

turn on a radiator