The Yonico 31340-SC 5/16" works as expected and makes a clean cut and dovetail joint on the Leigh D4R router guide. When purchasing an up spiral router This is a double flute straight cutter that comes with a Leigh pilot cutter designed to handle a lot of small "overshoots". This is NOT Lee's fault, it's the way straight flute cutters cut. Straight bits cut , splitting wood. Upward twist drills cut, cutting through the wood and throwing the scrap up and away from the next cut. The scrap thatโฆ