Added source code

utils/dogbones.scad

@@ -0,0 +1,46 @@
+//
+// NopSCADlib Copyright Chris Palmer 2018
+// nop.head@gmail.com
+// hydraraptor.blogspot.com
+//
+// This file is part of NopSCADlib.
+//
+// NopSCADlib is free software: you can redistribute it and/or modify it under the terms of the
+// GNU General Public License as published by the Free Software Foundation, either version 3 of
+// the License, or (at your option) any later version.
+//
+// NopSCADlib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with NopSCADlib.
+// If not, see <https://www.gnu.org/licenses/>.
+//
+
+//
+//! When square holes are cut with a CNC bit they get rounded corners. If it is important that
+//! a square cornered part fits in the hole then circles are placed in the corners making a bone shape.
+//
+include <../core.scad>
+
+module dogbone_square(size, r = cnc_bit_r, center = true) //! Square with circles at the corners
+{
+    union() {
+        square(size, center = center);
+
+        if(r > 0) {
+            origin = center ? [0, 0] : size / 2;
+            offset = r / sqrt(2);
+
+            for(x = [-1, 1], y = [-1, 1])
+                translate(origin + [x * (size.x / 2 - offset), y * (size.y / 2 - offset)])
+                    drill(r, 0);
+        }
+    }
+}
+
+module dogbone_rectangle(size, r = cnc_bit_r, center = true, xy_center = true) //! Rectangle with cylinders at the corners
+{
+    extrude_if(h = size.z, center = center)
+        dogbone_square([size.x, size.y], r, xy_center);
+}