diff --git a/cad/build.py b/cad/build.py
index bc12617..6629724 100644
--- a/cad/build.py
+++ b/cad/build.py
@@ -4,22 +4,63 @@ from build123d import *
 hole_offset = 20
 hole_diameter = 22
 
-width = 40
+core_width = 40
 thickness = 20
 
+screw_blocks_width = thickness
+screw_blocks_height = hole_offset
+screw_blocks_radius = 3
+
+screw_head_diameter = 8.5
+screw_head_depth = 5
+screw_body_diameter = 5
+
+track_width = 6.2
+track_height = 1.8
+
 assert (hole_offset - hole_diameter / 2) > 0
-assert (width - hole_diameter) > 0
+assert (core_width - hole_diameter) > 0
+assert (screw_blocks_width - (screw_blocks_radius * 2)) >= 0
+assert (hole_offset - screw_blocks_height) >= 0
 
 
 with BuildPart() as builder:
     with BuildSketch() as sketch:
         with BuildLine() as profile:
-            l1 = Polyline(
+            l1 = Line(
                 (0,0),
-                (width / 2, 0),
-                (width / 2, hole_offset)
+                ((core_width / 2) + screw_blocks_width, 0)
             )
-            l2 = CenterArc((0, hole_offset), width / 2, 90, -90)
+
+            polyline_path = (
+                l1 @ 1,
+                ((l1 @ 1).X, screw_blocks_height),
+                (core_width / 2, screw_blocks_height),
+            )
+            match (float)(hole_offset - screw_blocks_height):
+                case 0:
+                    FilletPolyline(
+                        *polyline_path,
+                        radius=screw_blocks_radius
+                    )
+                case len if len > 0 and len < screw_blocks_radius:
+                    sbl = FilletPolyline(
+                        *polyline_path,
+                        radius=screw_blocks_radius
+                    )
+                    Line(
+                        sbl @ 1,
+                        ((sbl @ 1).X, hole_offset)
+                    )
+                case len if len >= screw_blocks_radius:
+                    FilletPolyline(
+                        *polyline_path,
+                        (core_width / 2, hole_offset),
+                        radius=screw_blocks_radius
+                    )
+                case _: assert False
+
+            CenterArc((0, hole_offset), core_width / 2, 90, -90)
             mirror(profile.line, Plane.YZ)
         make_face()
 
@@ -29,5 +70,10 @@ with BuildPart() as builder:
     extrude(amount=thickness / 2)
     mirror(about=Plane.XY)
 
+    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:]):
+        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")