This is model of simple nutcracker. 
To make part stronger I recomended to use 3-4 perimeters and 5 top and bottoms solid layers and at least 70% of infill. 
Holes for M4 screws in lever should be tapped  M4 thread.
Hardware needed. 
-1x M6x60mm Socket Head Screw
-1x M6 Nylon Lock Nut
-2x Washer for M6 screw
-2x M4x16 or M4x20 Socket Head Screw

Material recomended: PET-G or stronger
Layer high: 0,3
Support needed
Infill at least 70%