diff --git a/follow_focus.py b/follow_focus.py
index 7663648..1b39bd8 100644
--- a/follow_focus.py
+++ b/follow_focus.py
@@ -7,45 +7,47 @@ from shapely.geometry import LineString
 from shapely.geometry import Point
 
 # M3 screws for attaching lid
-m3_tap=2.5
-m3_head_diameter=6
-m3_head_depth=3
-m3_passthrough=3.5
+m3_tap=              2.5
+m3_head_diameter=    6
+m3_head_depth=       3
+m3_passthrough=      3.5
 
 # Fastener dimensions
-fastener_width = 11
-fastener_height = 3.5
-fastener_length = 20
+fastener_width=      11
+fastener_height=     3.5
+fastener_length=     20
+fastener_h_spacing=  .2
 
 # NEMA 17 stepper motor
-stepper_motor_size=42.0
-stepper_hole_width=31.0
+stepper_motor_size=  42.0
+stepper_hole_width=  31.0
 
 # Case
-part_thinkness=20
-outer_fillets=2.5
-slant_degree=15.0
-wall_width=1.6
-loop_width=wall_width
-loop_angle=40
-rod_diameter=15.2
-offset=9
-tab_height=6
-tab_width=25
+part_thinkness=      20
+outer_fillets=       2.5
+slant_degree=        15.0
+wall_width=          1.6
+loop_width=          wall_width
+loop_angle=          40
+rod_diameter=        15.2
+offset=              9
+tab_height=          6
+tab_width=           25
 
 # Gears
-mod=0.8
-gear_gap=0.2
-gear_offset=0.5
-large_gear_diameter=8.5
-gear_thinkness=10
-sg_teeth=11
+mod=                 0.8
+gear_gap=            0.2
+gear_offset=         0.5
+large_gear_diameter= 8.5
+gear_thinkness=      10
+sg_teeth=            11
 
 # Other
-mount_gap=2
-support_radius=11/2
+mount_gap=           2
+support_radius=      11/2
 
 # Calculated values
+fastener_hole_depth = tab_height-2
 lid_thicknesss = (part_thinkness-gear_thinkness)/2
 gap = stepper_motor_size * math.sin(math.radians(slant_degree)) / math.sin(math.radians(90-slant_degree))
 width = math.sqrt(gap**2 + stepper_motor_size**2 - 2*gap*stepper_motor_size*math.cos(math.radians(90)))
@@ -170,8 +172,8 @@ base = base.faces('<<Y[-1]').workplane().center(-5,0).circle(6.5/2).cutBlind(-su
 base = base.faces('<<Y[-1]').workplane().circle(8.5/2).cutBlind(-support_radius-mount_gap)
 
 # Fastener
-base = base.faces('<<Y[-1]').workplane().circle((fastener_width+1)/2).cutBlind(-4)
-fastener = base.faces('<<Y[-4]').workplane().circle(fastener_width/2).extrude(4.5+fastener_height, combine=False)
+base = base.faces('<<Y[-1]').workplane().circle((fastener_width+1)/2).cutBlind(-fastener_hole_depth)
+fastener = base.faces('<<Y[-4]').workplane().circle(fastener_width/2).extrude(fastener_hole_depth+fastener_h_spacing+fastener_height, combine=False)
 fastener = fastener.faces('<<Y[-1]').workplane().center(-fastener_length,0)\
                                                 .line(20,-fastener_width/2)\
                                                 .vLine(fastener_width)\