module colop() {
difference() { // rough bottom 10mm of colop r40
    difference() { // outer edge of colop
        cylinder(h=10, d=55, center=true);
        difference() {
            cube([67,71,10], center=true); // outer box for cutter
            cube([47,67,10], center=true); // cutter's inner edge
        }
    }
    difference() { // inner edge of colop
        cylinder(h=10, d=47, center=true);
        difference() {
            cube([67,71,10], center=true); // outer box for cutter
            cube([42,67,10], center=true); // cutter's inner edge
        }
    }
}
}

colop();