Addded M3, M4 variants.

Thumb Screw/Thumb Screw.scad

@@ -7,7 +7,7 @@
 
 // M2: 4; M3: 5.5; M4: 7; M5: 8
 nut_size = 5.5; // [1:50]
-nut_height = 2.5; // [1:50]
+nut_height = 2.5; // [0:50]
 base_size = 20; // [1:50]
 base_height = 3; // [1:50]
 wall_size = 2.5; // [1:50]