diff --git a/nhf/joints.py b/nhf/joints.py
index b066c77..9cdd0ad 100644
--- a/nhf/joints.py
+++ b/nhf/joints.py
@@ -8,7 +8,8 @@ def hirth_joint(radius=60,
                 base_height=20,
                 n_tooth=16,
                 tooth_height=16,
-                tooth_height_inner=2):
+                tooth_height_inner=2,
+                tol=0.01):
     """
     Creates a cylindrical Hirth Joint
     """
@@ -26,14 +27,16 @@ def hirth_joint(radius=60,
     # triangles.
     outer = [
         (radius * math.tan(theta), 0),
+        (radius * math.tan(theta) - tol, 0),
         (0, tooth_height),
+        (-radius * math.tan(theta) + tol, 0),
         (-radius * math.tan(theta), 0),
     ]
     inner = [
         (radius_inner * math.sin(theta), 0),
-        (radius_inner * math.sin(theta), inner_raise - tooth_height_inner / 2),
-        (0, inner_raise + tooth_height_inner / 2),
-        (-radius_inner * math.sin(theta), inner_raise - tooth_height_inner / 2),
+        (radius_inner * math.sin(theta), inner_raise),
+        (0, inner_raise + tooth_height_inner),
+        (-radius_inner * math.sin(theta), inner_raise),
         (-radius_inner * math.sin(theta), 0),
     ]
     tooth = (
@@ -43,13 +46,13 @@ def hirth_joint(radius=60,
         .workplane(offset=radius - radius_inner)
         .polyline(outer)
         .close()
-        .loft(combine=True)
+        .loft(ruled=True, combine=True)
         .val()
     )
     tooth_centre_radius = radius_inner * math.cos(theta)
     teeth = (
         Cq.Workplane('XY')
-        .polarArray(radius=radius_inner, startAngle=0, angle=360, count=n_tooth)
+        .polarArray(radius=tooth_centre_radius, startAngle=0, angle=360, count=n_tooth)
         .eachpoint(lambda loc: tooth.located(loc))
         .intersect(Cq.Solid.makeCylinder(
             height=base_height + tooth_height,
@@ -67,7 +70,7 @@ def hirth_joint(radius=60,
         .clean()
     )
     #base.workplane(offset=tooth_height/2).circle(radius=radius,forConstruction=True).tag("mate")
-    base.polyline([(0, 0, 0), (0, 0, 1)], forConstruction=True).tag("mate")
+    base.polyline([(0, 0, base_height), (0, 0, base_height+tooth_height)], forConstruction=True).tag("mate")
     return base
 
 def hirth_assembly():
@@ -90,8 +93,8 @@ def hirth_assembly():
     result = (
         Cq.Assembly()
         .add(obj1, name="obj1", color=Cq.Color(0.8,0.8,0.5,0.3))
-        .add(obj2, name="obj2", color=Cq.Color(0.5,0.5,0.5,0.3), loc=Cq.Location((0,0,80)))
-        .constrain("obj1?mate", "obj2?mate", "Axis")
+        .add(obj2, name="obj2", color=Cq.Color(0.5,0.5,0.5,0.3))
+        .constrain("obj1?mate", "obj2?mate", "Plane")
         .solve()
     )
     return result