Small Engines (Lawn Mowers, etc.): black&decker electric mower, dremel tool, nuts bolts

Question
i hit arock while mowing which caused my blade to loosen up.  i cant get the nut to either ntighten up or loosen.  I HAVE STRIPPED THE MACHINE downto the armature which the blade is aattached to. the only to lock the shaft to put pressure on the nut is to clamp onto the armature any suggestions?  fffffffffffffffffffffffffffffffffffffffffffffff

Answer
Can you get a pipe wrench on the blade shaft...just above the nut?

Will the blade keep the armature shaft from turning?  If so, you can use a C clamp or two placed on the side of the deck to hold the blade, which holds the armature to remove the nut.

Air impact gun?
My personal favorite, dremel tool and split the nut in half...of course you will have to replace the nut.  This is actually common; I have an air powered die grinder with a cut-off wheel to split large, rusted or stripped nuts/bolts.

Let me know if the armature threads are damaged.
Eric