Slow Spiral, HSS M2 Fully Ground Replacement Drill BitsFor use with Drill Adapters, Counterbores and Adjustable Depth Stop Countersinks*.CNC CountersinkDrilling countersinks with these bits on the CNC machine is a great way to save time and have your pieces look great every time!With the adjustable depth drill bit you can adjust them for whatever size material you're working with. They are best used with a drilling toolpath, utilizing the peck drill option at 0.25" per pass with a 0.125" retract height.For best results run at 3,000 RPM with a 30 Inches Per Minute (IPM) plunge rate. No feed rate needs to be set with these as they only move up and down with the Z axis, not side to side. If your software doesn't allow a 0 feed rate, you can enter 1 IPM in the feed rate as a placeholder.*For 5/16" dia. round shank use a 7-8mm Spring Collet. For 3/8" dia. round shank use 9-10mm Spring Collet.