diff --git a/readme.md b/readme.md
index 8a52d2a..2891c9f 100644
--- a/readme.md
+++ b/readme.md
@@ -6173,18 +6173,18 @@ leaving a scar on either surface.
 ### Functions
 | Function | Description |
 |:--- |:--- |
-| `corrected_diameter(d, n = 0)` | Adjusted diameter to make flats lie on the circle |
-| `corrected_radius(r, n = 0)` | Adjusted radius to make flats lie on the circle |
-| `sides(r)` | Optimium number of sides for specified radius |
+| `corrected_diameter(d, n = undef)` | Adjusted diameter to make flats lie on the circle |
+| `corrected_radius(r, n = undef)` | Adjusted radius to make flats lie on the circle |
+| `sides(r, n = undef)` | Optimium number of sides for specified radius |
 
 ### Modules
 | Module | Description |
 |:--- |:--- |
 | `drill(r, h = 100, center = true)` | Make a cylinder for drilling holes suitable for CNC routing, set h = 0 for circle |
-| `poly_circle(r, sides = 0)` | Make a circle adjusted to print the correct size |
-| `poly_cylinder(r, h, center = false, sides = 0, chamfer = false, twist = 0)` | Make a cylinder adjusted to print the correct size |
+| `poly_circle(r, sides = undef)` | Make a circle adjusted to print the correct size |
+| `poly_cylinder(r, h, center = false, sides = undef, chamfer = false, twist = 0)` | Make a cylinder adjusted to print the correct size |
 | `poly_drill(r, h = 100, center = true)` | Make a cylinder for drilling holes suitable for CNC routing if cnc_bit_r is non zero, otherwise a poly_cylinder. |
-| `poly_ring(or, ir, sides = 0)` | Make a 2D ring adjusted to have the correct internal radius |
+| `poly_ring(or, ir, sides = undef)` | Make a 2D ring adjusted to have the correct internal radius |
 | `poly_tube(or, ir, h, center = false)` | Make a tube adjusted to have the correct internal radius |
 | `slot(r, l, h = 100)` | Make a horizontal slot suitable for CNC routing, set h = 0 for 2D version |
 
diff --git a/utils/core/polyholes.scad b/utils/core/polyholes.scad
index b8dcce2..6370b34 100644
--- a/utils/core/polyholes.scad
+++ b/utils/core/polyholes.scad
@@ -33,20 +33,20 @@
 //! When `twist` is set the resulting cylinder is extended by `eps` at each end so that the exact length of the hole can be used without
 //! leaving a scar on either surface.
 //
-function sides(r) = max(round(4 * r), 3);                                       //! Optimium number of sides for specified radius
-function corrected_radius(r, n = 0)   = r / cos(180 / (n ? n : sides(r)));      //! Adjusted radius to make flats lie on the circle
-function corrected_diameter(d, n = 0) = d / cos(180 / (n ? n : sides(d / 2)));  //! Adjusted diameter to make flats lie on the circle
+function sides(r, n = undef) = is_undef(n) ? max(round(4 * r), 3) : n ? max(n, 3) : r2sides(r); //! Optimium number of sides for specified radius
+function corrected_radius(r, n = undef)   = r / cos(180 / sides(r, n));                         //! Adjusted radius to make flats lie on the circle
+function corrected_diameter(d, n = undef) = 2 * corrected_radius(d / 2 , n);                    //! Adjusted diameter to make flats lie on the circle
 
-module poly_circle(r, sides = 0) { //! Make a circle adjusted to print the correct size
-    n = sides ? sides : sides(r);
-    circle(r = corrected_radius(r,n), $fn = n);
+module poly_circle(r, sides = undef) { //! Make a circle adjusted to print the correct size
+    n = sides(r, sides);
+    circle(r = corrected_radius(r, n), $fn = n);
 }
 
-module poly_cylinder(r, h, center = false, sides = 0, chamfer = false, twist = 0) {//! Make a cylinder adjusted to print the correct size
+module poly_cylinder(r, h, center = false, sides = undef, chamfer = false, twist = 0) {//! Make a cylinder adjusted to print the correct size
     if(twist) {
         slices = ceil(h / layer_height);
         twists = min(twist + 1, slices);
-        sides = sides ? sides : sides(r);
+        sides = sides(r, sides);
         rot = 360 / sides / twists * (twists < slices ? (1 + 1 / slices) : 1);
         if(center)
             for(side = [0, 1])
@@ -64,10 +64,10 @@ module poly_cylinder(r, h, center = false, sides = 0, chamfer = false, twist = 0
             poly_circle(r, sides);
 
     if(h && chamfer)
-        poly_cylinder(r + layer_height, center ? layer_height * 2 : layer_height, center, sides = sides ? sides : sides(r));
+        poly_cylinder(r + layer_height, center ? layer_height * 2 : layer_height, center, sides = sides(r, sides));
 }
 
-module poly_ring(or, ir, sides = 0) { //! Make a 2D ring adjusted to have the correct internal radius
+module poly_ring(or, ir, sides = undef) { //! Make a 2D ring adjusted to have the correct internal radius
     cir = corrected_radius(ir, sides);
     filaments = (or - cir) / extrusion_width;
     if(filaments > 3 + eps)