This is the Mechanical Shears model from 507 Mechanical Movements: http://507movements.com/mm_130.html
You will need a 5/16" dowel, 4x 5/8" #6 screws, 2x 1/4" #6 screws, and a rubber band. The crank, nut, and cams all have a flat on one side so shave or sand off a bit of that dowel. Try to make it fit as snug as possible. It is best to assemble everything on the dowel, pilot drill through handle, nut, and base, screw screws in, and cut the dowel ends flush.
See my blog post about this here: http://artofrandomness.net/blogs/matts-blog/mechanical-shears-maychanisms-4/