Add offset rings

offset-rings.scad

@@ -0,0 +1,23 @@
+/**
+ * Offset rings for tracing rough (eg jigsaw) cuts around templates
+ * to save some work for the mill
+ */
+
+H = 1; // Disc thickness
+Z = 0.2; // Hole thickness
+D = 1; // Hole diameter
+R = D / 2;
+
+module ring(i) {
+  difference() {
+    cylinder(h=H, r=25.4 * i, $fn=100);
+    cylinder(h=Z, r=R, $fn=50);
+    translate([0,0,Z]) cylinder(h=H-Z, r1=R, r2=R+2*(H-Z), $fn=50);
+  }
+}
+
+ring(1);                      // 25.4mm
+translate([50,0])  ring(3/4); // 19.05mm
+translate([100,0]) ring(1/2); // 12.7
+translate([150,0]) ring(3/8); // 9.52
+translate([200,0]) ring(1/4); // 6.35