Combination Drill/Tap Bits. 10-24NC. Complete Hole Drilling, Tapping and Deburring/Countersinking In One Operation With Power Drill Saves Labor and Time. Back Tapered Beyond Tap to Prevent Thread Damage From Over-Drilling. Deburr/Countersink Also Provided On Bit Beyond Back Taper. Made From Hardened High-Speed Steel VS. Carbon Steel For Longer Life. High Quality Hex Shank to Ensure Strong Connection to Drill Chuck. Designed to Tap Up to 10-Gauge Metal. Quick Change Adaptor Included In Both Metric A