diff --git a/motors.scad b/motors.scad
index 51f8d89..d575164 100644
--- a/motors.scad
+++ b/motors.scad
@@ -6,8 +6,7 @@ include <math.scad>
 
 
 //generates a motor mount for the specified nema standard #.
-module stepper_motor_mount(nema_standard,slide_distance=0, mochup=true)
-{
+module stepper_motor_mount(nema_standard,slide_distance=0, mochup=true, tolerance=0) {
 	//dimensions from:
 	// http://www.numberfactory.com/NEMA%20Motor%20Dimensions.htm
 	if (nema_standard == 17)
@@ -21,7 +20,8 @@ module stepper_motor_mount(nema_standard,slide_distance=0, mochup=true)
 			bolt_hole_size = 3.5,
 			bolt_hole_distance = 1.220*mm_per_inch,
 			slide_distance = slide_distance,
-			mochup = mochup);
+			mochup = mochup,
+			tolerance=tolerance);
 	}
 	if (nema_standard == 23)
 	{
@@ -34,7 +34,8 @@ module stepper_motor_mount(nema_standard,slide_distance=0, mochup=true)
 			bolt_hole_size = 0.195*mm_per_inch,
 			bolt_hole_distance = 1.856*mm_per_inch,
 			slide_distance = slide_distance,
-			mochup = mochup);
+			mochup = mochup,
+			tolerance=tolerance);
 	}
 	
 }
@@ -51,16 +52,17 @@ module _stepper_motor_mount(
 	bolt_hole_distance,
 	slide_distance = 0,
 	motor_length = 40, //arbitray - not standardized
-	mochup
+	mochup,
+	tolerance = 0
 )
 {
 	union()
 	{
 	// == centered mount points ==
 	//mounting circle inset
-	translate([0,slide_distance/2,0]) circle(r = pilot_diameter/2);
+	translate([0,slide_distance/2,0]) circle(r = pilot_diameter/2 + tolerance);
 	square([pilot_diameter,slide_distance],center=true);
-	translate([0,-slide_distance/2,0]) circle(r = pilot_diameter/2);
+	translate([0,-slide_distance/2,0]) circle(r = pilot_diameter/2 + tolerance);
 
 	//todo: motor shaft hole
 	
@@ -71,9 +73,9 @@ module _stepper_motor_mount(
 		{
 			translate([x*bolt_hole_distance/2,y*bolt_hole_distance/2,0])
 			{
-				translate([0,slide_distance/2,0]) circle(bolt_hole_size/2);
-				translate([0,-slide_distance/2,0]) circle(bolt_hole_size/2);
-				square([bolt_hole_size,slide_distance],center=true);
+				translate([0,slide_distance/2,0]) circle(bolt_hole_size/2 + tolerance);
+				translate([0,-slide_distance/2,0]) circle(bolt_hole_size/2 + tolerance);
+				square([bolt_hole_size+2*tolerance,slide_distance],center=true);
 			}
 		}
 	}