12kg is too weak???
i think it should be enough for me. anyway, i tried to drill a bigger hole into the plastic servo horn (the metal one is too hard and i don't have proper tool) and now it can fit the bolt. so thanks for the suggestion
however i face another problem. my servo just can't be centered and can't push the rod (to turn left).
i suspect it is affected by the screwdriver magnet. is there a way i can fix it or need to return the servo for replacement? or any chance it's not the servo fault?
thanks for the help guys!