diff --git a/nhf/touhou/shiki_eiki/crown.py b/nhf/touhou/shiki_eiki/crown.py
index 8f9ef91..9cc6849 100644
--- a/nhf/touhou/shiki_eiki/crown.py
+++ b/nhf/touhou/shiki_eiki/crown.py
@@ -47,7 +47,7 @@ class Crown(Model):
     # brass insert thickness
     slot_thickness: float = 2.0
     slot_width: float = 20.0
-    slot_tilt: float = 45
+    slot_tilt: float = 60
 
     material: Material = Material.METAL_BRASS
     material_side: Material = Material.PLASTIC_PLA
@@ -414,15 +414,17 @@ class Crown(Model):
 
     def side_guard_frontal_slot(self) -> Cq.Workplane:
         angle = 360 / self.facets
+        inner_d = self.thickness / 2 - self.slot_thickness / 2
+        outer_d = self.thickness / 2 + self.slot_thickness / 2
         outer = Cq.Solid.makeCone(
-            radius1=self.radius_lower_front + self.thickness,
-            radius2=self.radius_upper_front + self.thickness,
+            radius1=self.radius_lower_front + outer_d,
+            radius2=self.radius_upper_front + outer_d,
             height=self.height,
             angleDegrees=angle,
         )
         inner = Cq.Solid.makeCone(
-            radius1=self.radius_lower_front,
-            radius2=self.radius_upper_front,
+            radius1=self.radius_lower_front + inner_d,
+            radius2=self.radius_upper_front + inner_d,
             height=self.height,
             angleDegrees=angle,
         )
@@ -486,17 +488,27 @@ class Crown(Model):
         #)
         result = shell * profile# - channel
 
-        # Create the slots
+        # Create the downward slots
         for sign in [-1, 1]:
-            slot = Cq.Solid.makeBox(
+            slot_box = Cq.Solid.makeBox(
                 length=self.height,
                 width=self.slot_width,
                 height=self.slot_thickness,
             ).moved(
+                Cq.Location(-self.slot_thickness,-self.slot_width/2, -self.slot_thickness/2)
+            )
+            # keyhole for threads to stay in place
+            slot_cyl = Cq.Solid.makeCylinder(
+                radius=self.slot_thickness/2,
+                height=self.height,
+                pnt=(0,0,self.slot_thickness/2),
+                dir=(1,0,0),
+            )
+            slot = slot_box + slot_cyl
+            slot = slot.moved(
                 Cq.Location.rot2d(sign * self.side_guard_slot_angle) *
                 Cq.Location(self.radius_lower + self.side_guard_thickness/2, 0, 0) *
-                Cq.Location(0,0,0,0,-180 + self.slot_tilt,0) *
-                Cq.Location(-self.slot_thickness,-self.slot_width/2, -self.slot_thickness/2)
+                Cq.Location(0,0,0,0,-180 + self.slot_tilt,0)
             )
             result = result - slot
 
@@ -553,7 +565,7 @@ class Crown(Model):
             attach_left=AttachPoint.DOVETAIL_OUT,
             attach_right=AttachPoint.DOVETAIL_IN,
         )
-    @target(name="side_guard_3")
+    @target(name="side_guard_4")
     def side_guard_4(self) -> Cq.Workplane:
         return self.side_guard(
             attach_left=AttachPoint.DOVETAIL_OUT,