diff --git a/attachments.scad b/attachments.scad
index 7a9da05..412c8c7 100644
--- a/attachments.scad
+++ b/attachments.scad
@@ -1723,11 +1723,26 @@ module face_profile(faces=[], r, d, excess=0.01, convexity=10) {
 //   `$idx` is set to the index number of each edge.
 //   `$attach_anchor` is set for each edge given, to the `[ANCHOR, POSITION, ORIENT, SPIN]` information for that anchor.
 //   `$profile_type` is set to `"edge"`.
+//   `$edge_angle` is set to the inner angle of the current edge.
 // Example:
 //   diff()
 //   cube([50,60,70],center=true)
 //       edge_profile([TOP,"Z"],except=[BACK,TOP+LEFT])
 //           mask2d_roundover(r=10, inset=2);
+// Example: Using $edge_angle on a Conoid
+//   diff()
+//   cyl(d1=50, d2=30, l=40, anchor=BOT) {
+//       edge_profile([TOP,BOT], excess=10, convexity=6) {
+//           mask2d_roundover(r=8, inset=1, excess=1, mask_angle=$edge_angle);
+//       }
+//   }
+// Example: Using $edge_angle on a Prismoid
+//   diff()
+//   prismoid([60,50],[30,20],h=40,shift=[-25,15]) {
+//       edge_profile(excess=10, convexity=20) {
+//           mask2d_roundover(r=5,inset=1,mask_angle=$edge_angle);
+//       }
+//   }
 
 module edge_profile(edges=EDGES_ALL, except=[], excess=0.01, convexity=10) {
     req_children($children);
@@ -1769,9 +1784,9 @@ module edge_profile(edges=EDGES_ALL, except=[], excess=0.01, convexity=10) {
                 if (!approx(pt1,pt2)) {
                     seglen = norm(pt2-pt1) + 2 * excess;
                     move(cp) {
-                        frame_map(y=-v1, z=unit(pt2-pt1)) {
+                        frame_map(x=-v2, z=unit(pt2-pt1)) {
                             linear_extrude(height=seglen, center=true, convexity=convexity)
-                                children();
+                                mirror([-1,1]) children();
                         }
                     }
                 }
diff --git a/gears.scad b/gears.scad
index 516ace4..9b966db 100644
--- a/gears.scad
+++ b/gears.scad
@@ -203,7 +203,7 @@ function spur_gear(
         p = pitch_radius(pitch, teeth),
         c = outer_radius(pitch, teeth, clearance, internal),
         r = _root_radius(pitch, teeth, clearance, internal),
-        twist = atan2(thickness*tan(helical),p),
+        twist = 360*thickness*tan(helical)/(2*PI*p),
         rgn = [
             spur_gear2d(
                 pitch = pitch,
@@ -245,7 +245,7 @@ module spur_gear(
     p = pitch_radius(pitch, teeth);
     c = outer_radius(pitch, teeth, clearance, internal);
     r = _root_radius(pitch, teeth, clearance, internal);
-    twist = atan2(thickness*tan(helical),p);
+    twist = 360*thickness*tan(helical)/(2*PI*p);
     default_tag("remove", internal)
         attachable(anchor,spin,orient, r=p, l=thickness) {
             zrot(twist/2)
@@ -268,7 +268,7 @@ module spur_gear(
                         circle(r=shaft_diam/2, $fn=max(12,segs(shaft_diam/2)));
                     }
                 }
-              }
+            }
             children();
         }
 }