Click on the highlighted URL below my name here titled "Knifemakers Supplies" and you will find the button lock design.
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The metal cutting hack saw blade you're talking about is probably made of M2 high speed steel. That will make a great blade but can't be drilled with HSS drills. You'd have to use carbide tools.
I suggest you try to find a piece of A2 or D2 tool steel, used everywhere to make dies and punches for industrial metalworking. That would have to be heat treated after it's formed to shape.
Welcome to the forums, Croatia man.
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