Fix countersinking countersunk bolts

When we countersink socket head bolts, we only need to apply additional
head clearance when we exceed 1 heads worth of countersink (`countersink
> 1`). With countersunk screws, since the head is part of the bolt
length, this applies to any `countersink > 0`.

Author: mmalecki

catchnhole.scad

@@ -122,7 +122,10 @@ module bolt (
           b,
           kind,
           head_diameter_clearance,
-          head_top_clearance = max((countersink - 1) * head_length, 0) + head_top_clearance,
+          head_top_clearance = max(
+            (countersink - (kind == "countersunk" ? 0 : 1)) * head_length,
+            0
+          ) + head_top_clearance
         );
       }
     }

examples/simple.scad

@@ -23,9 +23,14 @@ difference () {
 
 
   // An M5 nutcatch with a countersunk screw:
-  translate([10, 0, 0]) {
+  translate([10, b * 1/4, 0]) {
     nutcatch_parallel("M5");
-    bolt("M5", 25, kind = "countersunk");
+    bolt("M5", h, kind = "countersunk");
+  }
+
+  // And just a countersunk M5 with a countersunk screw:
+  translate([10, -b / 4, 0]) {
+    bolt("M5", h, kind = "countersunk", countersink = 1);
   }
 
   // An M8 nutcatch with a socket head countersunk screw: