SIX_INCH=152;
OUTER_RIM_WIDTH=4;
CUTTER_HEIGHT=12;

difference() {
  linear_extrude(2)
    circle(d=(SIX_INCH+(OUTER_RIM_WIDTH*2)), center=True, $fn=200);
  linear_extrude(3) circle(d=SIX_INCH, center=True, $fn=200);
}

linear_extrude(CUTTER_HEIGHT) {
    difference() {
    circle(d=(SIX_INCH+(.6*2)), center=True, $fn=200);
    circle(d=SIX_INCH, center=True, $fn=200);
  }
}