diff --git a/cad/build.py b/cad/build.py
index cbf25a1..e2090ac 100644
--- a/cad/build.py
+++ b/cad/build.py
@@ -102,6 +102,8 @@ def build_drive_shaft_bar_adapter():
     thickness = 10
 
     ext_screw_hole_diam = 6
+    ext_screw_hole_head_diam = 10.5
+    ext_screw_hole_head_depth = 1
     ext_screw_hole_offset = 10
 
     shaft_hub_bore_diam = 8
@@ -131,9 +133,9 @@ def build_drive_shaft_bar_adapter():
             with BuildPart(screws_origin, mode=Mode.SUBTRACT) as ext_track_cut_out:
                 Box(ext_size, ext_size, ext_screw_hole_diam + 8)
                 chamfer(ext_track_cut_out.edges(), 3)
-            with PolarLocations(0, 4):
+            with PolarLocations((ext_size / 2) + thickness, 4):
                 with Locations(Rotation(0, 90, 0)):
-                    Hole(ext_screw_hole_diam / 2)
+                    CounterBoreHole(ext_screw_hole_diam / 2, ext_screw_hole_head_diam / 2, ext_screw_hole_head_depth)
 
         # shaft interface
         with Locations(drive_shaft_bar_adapter.faces().filter_by(Plane.XY).sort_by(Axis.Z)[1].offset(shaft_hub_screw_head_depth)):