Change motor shaft diameter

Looks like printing with good printer makes this hole too large.
The captive nut then pushes the shaft when thightened unevenly,
ending up with the gear not turning around the shaft correctly.

3d_models/gears.scad

@@ -21,7 +21,7 @@ gear_shaft_h = 6;
 // GEAR1 (SMALLER GEAR, STEPPER GEAR) OPTIONS:
 // It's helpful to choose prime numbers for the gear teeth.
 gear1_teeth = 13;
-gear1_shaft_d = 5.5;  			// diameter of motor shaft
+gear1_shaft_d = 5.1;  			// diameter of motor shaft
 gear1_shaft_r  = gear1_shaft_d/2;	
 // gear1 shaft assumed to fill entire gear.
 // gear1 attaches by means of a captive nut and bolt (or actual setscrew)