|
A couple of drops of penetrating oil or WD sitting overnight should help, galvanic corrosion between the screw and the aluminium knob, careful hitting it with an impact as you may damage the valve.
Heating the aluminium will probably make it tighter.
With larger flat head screws a hit with a small hammer and punch usually would break the taper free but you have the valve to protect.
__________________
87 930,
|