To make a router guide bush, the router bit should be fully inserted into the collet. Then, before closing the collet nuts, pull it back out by 1/8 inch to check the fit. Sand the edges of the boards before routing them to ensure that the guide bearing rides on a single layer when routing. Firmly press the router’s base against the wood ground to ensure the router from tipping. Set the cutter depth to a shallow cut, then rout all four edges of the piece of wood. Adjust the router and reverse the procedure once you’ve achieved a deeper cut.