diff --git a/boxes/__init__.py b/boxes/__init__.py
index f04a3bf..15c9f2d 100755
--- a/boxes/__init__.py
+++ b/boxes/__init__.py
@@ -29,6 +29,7 @@ from boxes import edges
 from boxes import formats
 from boxes import gears
 from boxes import pulley
+from boxes import parts
 
 ### Helpers
 
@@ -346,6 +347,7 @@ class Boxes:
         # Gears
         self.addPart(gears.Gears(self))
         self.addPart(pulley.Pulley(self))
+        self.addPart(parts.Parts(self))
 
     def adjustSize(self, l, e1=True, e2=True):
         try:
diff --git a/boxes/parts.py b/boxes/parts.py
new file mode 100644
index 0000000..1bc43e0
--- /dev/null
+++ b/boxes/parts.py
@@ -0,0 +1,81 @@
+from math import *
+
+def arcOnCircle(spanning_angle, outgoing_angle, r=1.0):
+    angle = spanning_angle+2*outgoing_angle
+    radius = r * sin(radians(0.5*spanning_angle))/sin(radians(180-outgoing_angle-0.5*spanning_angle))
+    return angle, abs(radius)
+
+class Parts:
+
+    def __init__(self, boxes):
+        self.boxes = boxes
+    """
+    def roundKnob(self, diameter, n=20, callback=None, move=""):
+        size = diameter+diameter/n+2*spacing
+        if self.move(size, size, move, before=True):
+            return
+        self.boxes.ctx.save()
+        self.moveTo(size/2, size/2)
+        self.cc(callback, None, 0, 0)
+        
+        self.boxes.ctx.restore()
+        self.move(size, size, move, before=True)
+    """
+
+    def __getattr__(self, name):
+        return getattr(self.boxes, name)
+    
+    def disc(self, diameter, callback=None, move=""):
+        size = diameter+2*spacing
+        r = diameter/2.0
+        if self.move(size, size, move, before=True):
+            return
+        self.boxes.ctx.save()
+        self.moveTo(size/2, size/2)
+        self.cc(callback, None, 0, 0)
+        self.moveTo(r+self.burn,0, 90)
+        self.corner(360, r)
+        self.boxes.ctx.restore()
+        self.move(size, size, move, before=True)
+        
+    def waivyKnob(self, diameter, n=20, angle=45, callback=None, move=""):
+        size = diameter+pi*diameter/n+2*self.boxes.spacing
+        if self.move(size, size, move, before=True):
+            return
+        self.boxes.ctx.save()
+        self.moveTo(size/2, size/2)
+        self.cc(callback, None, 0, 0)
+        self.moveTo(diameter/2, 0, angle)
+        a, r = arcOnCircle(360./n, angle, diameter/2)
+        a2, r2 = arcOnCircle(360./n, -angle, diameter/2)
+        for i in range(n//2):
+            self.boxes.corner(a, r)
+            self.boxes.corner(a2, r2)
+        self.boxes.ctx.restore()
+        self.move(size, size, move, before=True)
+
+    def concaveKnob(self, diameter, n=3, rounded=0.2, angle=70, callback=None, move=""):
+        size = diameter+2*self.boxes.spacing
+        if self.move(size, size, move, before=True):
+            return
+        self.boxes.ctx.save()
+        self.rectangularHole(size/2, size/2, size, size)
+        self.moveTo(size/2, size/2)
+        self.hole(0,0, 3)
+        self.hole(0,0, diameter/2)
+        self.cc(callback, None, 0, 0)
+        self.moveTo(diameter/2, 0, 90+angle)
+        a, r = arcOnCircle(360./n*(1-rounded), -angle, diameter/2)
+        print(360./n*(1-rounded), a, r)
+        if abs(a) < 0.01: # avoid trying to make a straight line as an arc
+            a, r = arcOnCircle(360./n*(1-rounded), -angle-0.01, diameter/2)            
+        print(a, r)
+        for i in range(n):
+            self.boxes.corner(a, r)
+            self.corner(angle)
+            self.corner(360./n*rounded, diameter/2)
+            self.corner(angle)
+        self.boxes.ctx.restore()
+        self.move(size, size, move, before=True)
+    
+