ERF Filametrix #4 hobby knife snapping jig

The ERF Filametrix toolhead mod for the ERCF MMU calls for a specially sized #4 hobby knife blade.  Since the blades are made of hardened steel, this seems like a very difficult thing to cut.  However, since the metal is quite brittle and very thin, it's easy to snap the end off.

I designed a jig to help with snapping the Filametrix scalpel blade to the right length. I made three different variants, since I found the 26mm length was too long for my toolhead and it interfered with the filament path even when retracted.

I printed these with 0.2 layer height and 40% infill in PLA.

Instructions:

1. Clamp the two parts together in a vice, just enough to force the alignment pins into their holes.  But not super tight yet.  We want a bit of room so we can put the blade in.
2. Carefully place the scalpel blade into the slot. The sharp end goes inside, and the other end sticks out.  Make sure the blade is all the way in, and aligned with the slot.
3. Now, tighten the vice so the blade won't move.
4. Use a pair of pliers to bend the blade back and forth until it snaps. It should only take one or two back-and-forth motions.
5. I used a credit card diamond sharpening stone to ease any remaining edge that didn't snap off cleanly.

These blades are sharp!  Please be careful not to cut yourself.  I am not responsible for any injuries.