these weapons are illegal in some states.
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Step 1: Homemade Butterfly Knife
your gunna need a measuring tape, a disc cutter, a pen or a marker, and some nuts and bolts.
measure out the handles (what size you want) and mark the measurements.
take the disc cutter and cut out 4 handles.
do the same thing with the blade and drill 2 holes in each handle.
(making this knife may take a few tries to get it right).
take the screws and slide them threw the holes and bold them on.
you might have to grind the screws down with a bench grinder or a disc cutter.
to sharpen the blade, first shape it out to the way you want it and work on grinding it down, again, with the bench grinder or disc cutter.
Step 2: Homemade Butterfly Knife
this is where you will find some sort of metal pin to place in the tang.
i used 2 thick wood staples and twisted them with pliers.