removing tight/stuck blade bolt

[bertsmobile1]

Unless the blade has a star type pattern the blade will self tghten during use
If you cant shift it chop the head off the remaining bolt will unscrew with your fingers .

 

[Bertrrr]

Penetrating oil will not penetrate a stuck bolt , good to use after it begins to move into a rusted thread area but it will not help a stuck bolt begin to move

 

[bertsmobile1]

Never found a rusted on blade bolt except for the tips of swing backs.
All spindle mounts are always overtightened
Some times cutting an X through the head will relieve enough tension to remove them but if I am under there with th 1mm cut off wheel, 3 cuts then a wack with a cold chisel will break the head off .