Mat board push cutter, similar to a Logan push style bevel cutter. The cutting angle is set to 52 degrees and it was designed to cut 4 ply mat board (~1/16"). There are 7 unique parts to this build, two being 3D printed parts, a razor blade, melt-in style nuts, and 3 different sized #4-40 screws. If someone wanted me to redesign the cutter with smaller holes that could be tapped or used with self-tapping screws I'd be happy to do so. Also I could make the unit cut thicker (say 8 ply 1/8") mat board, which I plan to do if I ever get some thick mat but I'll make that a new part designation as I want the centered cutting mark on the units back to reflect the true cutting point.
To assemble: Clean up all the edges of the printed parts and press in the #4-40 nuts using a fine tipped soldering iron. Nuts should be flush or slightly below the surface. File down any plastic that is pushed above the back surface and also re-tap the threads to remove any plastic that gets into the nut's lower threads (or just use shorter screws than listed). Attached the base and the blade holder using the #4-40 X 1/2" screw as shown. Torque screw down till a fair amount of resistance is needed to rotate the blade holder, you'll need to use you own judgement here. You can put a ever-so-little dab of Loc-Tite on the screw but don't let it come into contact with the plastic as it could cause the plastic to get brittle and crank over time. Install the blade onto the blade holder and set the correct cutting depth by adjusting the set-screw on the bottom or the base. The tip of the blade should be just below the bottom surface of the material to be cut. Then start cutting or watch a Logan mat cutter tutorial video on Youtube.
I used 1.2 mm walls so there was some good meat for the press-in nuts to adhere to.