diff --git a/freecad/gears/cycloidgear.py b/freecad/gears/cycloidgear.py
index fa6e859..d35dc85 100644
--- a/freecad/gears/cycloidgear.py
+++ b/freecad/gears/cycloidgear.py
@@ -201,10 +201,11 @@ class CycloidGear(BaseGear):
         )  # set read-only after setting the expression, else it won't be visible. bug?
 
     def generate_gear_shape(self, fp):
+        fp.gear.num_teeth = fp.num_teeth
         fp.gear.m = fp.module.Value
         fp.dw = fp.module * fp.num_teeth
-        fp.gear.z1 = fp.inner_diameter
-        fp.gear.z2 = fp.outer_diameter
+        fp.gear.num_teeth_1 = fp.inner_diameter
+        fp.gear.num_teeth_2 = fp.outer_diameter
         fp.gear.clearance = fp.clearance
         fp.gear.head = fp.head
         fp.gear.backlash = fp.backlash.Value
diff --git a/freecad/gears/involutegear.py b/freecad/gears/involutegear.py
index 9948163..8cf5520 100644
--- a/freecad/gears/involutegear.py
+++ b/freecad/gears/involutegear.py
@@ -287,6 +287,7 @@ class InvoluteGear(BaseGear):
         obj.gear.backlash = obj.backlash.Value * (-obj.reversed_backlash + 0.5) * 2.0
         obj.gear.head = obj.head
         obj.gear.properties_from_tool = obj.properties_from_tool
+        obj.gear.num_teeth = obj.num_teeth
 
         obj.gear._update()
         self.compute_traverse_properties(obj)
diff --git a/pygears/cycloid_tooth.py b/pygears/cycloid_tooth.py
index 14e2d97..3089ef1 100644
--- a/pygears/cycloid_tooth.py
+++ b/pygears/cycloid_tooth.py
@@ -21,24 +21,24 @@ from ._functions import rotation, reflection
 
 
 class CycloidTooth:
-    def __init__(self, z1=5, z2=5, z=14, m=5, clearance=0.25, backlash=0.00, head=0.0):
+    def __init__(self, num_teeth_1=5, num_teeth_2=5, num_teeth=14, m=5, clearance=0.25, backlash=0.00, head=0.0):
         self.m = m
-        self.z = z
+        self.num_teeth = num_teeth
         self.clearance = clearance
         self.backlash = backlash
-        self.z1 = z1
-        self.z2 = z2
+        self.num_teeth_1 = num_teeth_1
+        self.num_teeth_2 = num_teeth_2
         self.head = head
         self._calc_gear_factors()
 
     def _calc_gear_factors(self):
-        self.d1 = self.z1 * self.m
-        self.d2 = self.z2 * self.m
+        self.d1 = self.num_teeth_1 * self.m
+        self.d2 = self.num_teeth_2 * self.m
         self.phi = self.m * pi
-        self.d = self.z * self.m
+        self.d = self.num_teeth * self.m
         self.da = self.d + 2 * (1 + self.head) * self.m
         self.di = self.d - 2 * (1 + self.clearance) * self.m
-        self.phipart = 2 * pi / self.z
+        self.phipart = 2 * pi / self.num_teeth
         self.angular_backlash = self.backlash / (self.d / 2)
 
     def epicycloid_x(self):
@@ -120,9 +120,9 @@ class CycloidTooth:
     def _update(self):
         self.__init__(
             m=self.m,
-            z=self.z,
-            z1=self.z1,
-            z2=self.z2,
+            num_teeth=self.num_teeth,
+            num_teeth_1=self.num_teeth_1,
+            num_teeth_2=self.num_teeth_2,
             clearance=self.clearance,
             backlash=self.backlash,
             head=self.head,
diff --git a/pygears/involute_tooth.py b/pygears/involute_tooth.py
index bde0123..4b4a23b 100644
--- a/pygears/involute_tooth.py
+++ b/pygears/involute_tooth.py
@@ -43,7 +43,7 @@ class InvoluteTooth:
     def __init__(
         self,
         m=5,
-        z=15,
+        num_teeth=15,
         pressure_angle=20 * pi / 180.0,
         clearance=0.12,
         shift=0.5,
@@ -56,7 +56,7 @@ class InvoluteTooth:
         self.pressure_angle = pressure_angle
         self.beta = beta
         self.m_n = m
-        self.z = z
+        self.num_teeth = num_teeth
         self.undercut = undercut
         self.shift = shift
         self.clearance = clearance
@@ -76,12 +76,12 @@ class InvoluteTooth:
         self.pitch = self.m * pi
         self.c = self.clearance * self.m_n
         self.midpoint = [0.0, 0.0]
-        self.d = self.z * self.m
-        self.dw = self.m * self.z
+        self.d = self.num_teeth * self.m
+        self.dw = self.m * self.num_teeth
         self.da = self.dw + 2.0 * self.m_n + 2.0 * (self.shift + self.head) * self.m_n
         self.df = self.dw - 2.0 * self.m_n - 2 * self.c + 2.0 * self.shift * self.m_n
         self.dg = self.d * cos(self.pressure_angle_t)
-        self.phipart = 2 * pi / self.z
+        self.phipart = 2 * pi / self.num_teeth
 
         self.undercut_end = sqrt(-(self.df**2) + self.da**2) / self.da
         self.undercut_rot = (
@@ -109,7 +109,7 @@ class InvoluteTooth:
             self.m / (self.d) * (pi / 2 + 2 * self.shift * tan(self.pressure_angle_t))
         )
         self.involute_rot2 = (
-            1 / self.z * (pi / 2 + 2 * self.shift * tan(self.pressure_angle_t))
+            1 / self.num_teeth * (pi / 2 + 2 * self.shift * tan(self.pressure_angle_t))
         )
         self.involute_rot = self.involute_rot1 + self.involute_rot2
         self.angular_backlash = self.backlash / (self.d / 2)
@@ -206,7 +206,7 @@ class InvoluteRack(object):
     def __init__(
         self,
         m=5,
-        z=15,
+        num_teeth=15,
         pressure_angle=20 * pi / 180.0,
         thickness=5,
         beta=0,
@@ -219,7 +219,7 @@ class InvoluteRack(object):
         self.pressure_angle = pressure_angle
         self.thickness = thickness
         self.m = m
-        self.z = z
+        self.num_teeth = num_teeth
         self.beta = beta
         self.head = head
         self.clearance = clearance
@@ -247,8 +247,8 @@ class InvoluteRack(object):
         ]
         teeth = [tooth]
         trans = translation([0.0, pitch, 0.0])
-        for i in range(self.z - 1):
-            if self.simplified and i > 3 and i < (self.z - 6):
+        for i in range(self.num_teeth - 1):
+            if self.simplified and i > 3 and i < (self.num_teeth - 6):
                 tooth = trans(tooth).tolist()
             else:
                 tooth = trans(tooth).tolist()
@@ -258,7 +258,7 @@ class InvoluteRack(object):
                     teeth[-1].pop()
                     teeth[-1][-1][0] = 0
                     teeth[-1][-1][1] -= a / 2
-                if self.simplified and (i == self.z - 6):
+                if self.simplified and (i == self.num_teeth - 6):
                     teeth[-1].pop(0)
                     teeth[-1].pop(0)
                     teeth[-1][0][0] = 0