diff --git a/screw.scad b/screw.scad
index 917350c..c60ef1b 100644
--- a/screw.scad
+++ b/screw.scad
@@ -1,3 +1,5 @@
+include <curves.scad>
+
 /* common screw parameter
 length
 pitch = length/rotations: the distance between the turns of the thread
@@ -5,30 +7,48 @@ outside_diameter
 inner_diameter: thickness of the shaft
 */
 
-module helix(pitch, length){
 
+module helix(pitch, length, slices=500){
+    rotations = length/pitch;
+    linear_extrude(height=length, center=false, convexity=10, twist=360*rotations, slices=slices, $fn=100)
+        child(0);
 }
 
 module auger(pitch, length, outside_diameter, inner_diameter) {
-    rotations = length/pitch;
-	union() {
-		linear_extrude(height=length, center=false, convexity=10, twist=360*rotations, slices=100, $fn=1000)
-			polygon(points=[[10,10],[100,1],[100,-1],[10,-10]], paths=[[0,1,2,3]]);
-		cylinder(h=length, r=20);
-	}
+    union(){
+        helix(pitch, length)
+        polygon(points=[[10,10],[100,1],[100,-1],[10,-10]], paths=[[0,1,2,3]]);
+        cylinder(h=length, r=20);
+    }
 }
 
 translate([300, 0, 0]) auger(100, 300);
 
 
-module ball_groove(pitch, rotations, diameter, bearing_radius=10) {
-    rotations = length/pitch;
-    linear_extrude(height = 10, center = false, convexity = 10, twist = 360, $fn = 1000)
+module ball_groove(pitch, length, diameter, ball_radius=10) {
+    helix(pitch, length, slices=100)
         translate([diameter, 0, 0])
-        circle(r = bearing_radius);
+        circle(r = ball_radius);
 }
 
-ball_groove(100, 300, 10);
+translate([0, 300, 0]) ball_groove(100, 300, 10);
+
+
+module ball_groove2(pitch, length, diameter, ball_radius, slices=200){
+    rotations = length/pitch;
+    radius=diameter/2;
+    offset = length/slices;
+    union(){
+        for (i = [0:slices]) {
+            assign (z = i*offset){
+                translate(helix_curve(pitch, radius, z)) sphere(ball_radius, $fa=5, $fs=1);
+            }
+        }
+    }
+}
+
+translate([0, 0, 0]) ball_groove2(100, 300, 100, 10);
+
 
 module ball_screw(pitch, length, bearing_radius=2) {