These drill press cutters will give you professional results every time and because they have extra thick carbide tips, they will outlast and out perform steel cutters by up to 50 times. Improved design gives cleaner cut with less tear out. New miniature sizes for small boxes. All cutters 1/2" shank. To be used on heavy duty drill press or machine milling only. Recommended RPM is 1800 to 3000 based on the type of wood used. The harder the wood, the slower the RPM. When using in drill press, gradual, very slow feed rate is advised.