diff --git a/cad/build.py b/cad/build.py
index fe93a44..cc39096 100644
--- a/cad/build.py
+++ b/cad/build.py
@@ -27,7 +27,7 @@ assert (screw_blocks_width - (screw_blocks_radius * 2)) >= 0
 assert (bearing_offset - screw_blocks_height) >= 0
 
 
-with BuildPart() as builder:
+with BuildPart() as drive_shaft_mount:
     with BuildSketch() as sketch:
         with BuildLine() as profile:
             l1 = Line(
@@ -73,14 +73,14 @@ with BuildPart() as builder:
     extrude(amount=thickness / 2)
     mirror(about=Plane.XY)
 
-    with Locations((0, bearing_offset, builder.faces().sort_by(Axis.Z)[-1].center().Z)):
+    with Locations((0, bearing_offset, drive_shaft_mount.faces().sort_by(Axis.Z)[-1].center().Z)):
         Hole(bearing_diameter / 2, (thickness / 2) + (bearing_height / 2))
         Hole(shaft_clearance_diameter / 2, (thickness / 2) - (bearing_height / 2))
 
     Box(core_width + (screw_blocks_width * 2), track_width, track_height, (90, 0, 0), (Align.CENTER, Align.CENTER, Align.MIN))
 
-    with Locations(builder.faces().filter_by(Plane.XZ).sort_by(Axis.Y)[-2:]):
+    with Locations(drive_shaft_mount.faces().filter_by(Plane.XZ).sort_by(Axis.Y)[-2:]):
         CounterBoreHole(screw_body_diameter / 2, screw_head_diameter / 2, screw_head_depth)
 
-assert builder.part is not None
-export_step(builder.part, "drive shaft mount.step")
+assert drive_shaft_mount.part is not None
+export_step(drive_shaft_mount.part, "drive shaft mount.step")