I'm trying to mount a ceiling fan on an older electrical box... I need to buy some longer screws so it will fit, does anyone know what the standard size screw would be for the ones in the corner ? Please se image .
Most likely 8-32, possibly 6-32. Watch out, 8-32 is fine thread.
The -32 is intentional as it assures enough thread engagement.
Make sure you are hanging your fan by more than just a couple #8 screws!