diff --git a/pygears/involute_tooth.py b/pygears/involute_tooth.py
index c0e02ce..7fdd7dc 100644
--- a/pygears/involute_tooth.py
+++ b/pygears/involute_tooth.py
@@ -180,17 +180,19 @@ class InvoluteRack(object):
         if self.properties_from_tool:
             pressure_angle_t = arctan(tan(self.pressure_angle) / cos(self.beta))
             m = self.m / cos(self.beta)
+            m_n = self.m
         else:
             pressure_angle_t = self.pressure_angle
             m = self.m
+            m_n  = self.m
 
-        a = (2 + self.head + self.clearence) * m * tan(pressure_angle_t)
-        b = (m * pi) / 4 - (1 + self.head) * m * tan(pressure_angle_t)
+        a = (2 + self.head + self.clearence) * m_n * tan(pressure_angle_t)
+        b = (m * pi) / 4 - (1 + self.head) * m_n * tan(pressure_angle_t)
         tooth = [
-            [-self.m * (1 + self.clearence), -a - b],
-            [self.m * (1 + self.head), -b],
-            [self.m * (1 + self.head), b],
-            [-self.m * (1 + self.clearence), a + b]
+            [-m_n * (1 + self.clearence), -a - b],
+            [m_n * (1 + self.head), -b],
+            [m_n * (1 + self.head), b],
+            [-m_n * (1 + self.clearence), a + b]
         ]
         teeth = [tooth]
         trans = translation([0., m * pi, 0.])