1/4-20NC Combination Drill Tap Bits. Drill, Tap, and Countersink in one easy to use bit. Tap holes up to 4X's faster than traditional methods. One-piece Drill/Tap design ensures proper hole size for threaded tap size. Available kit and individual bits in 8-32NC, 10-32NF, and 1/4-20NC thread sizes. Constructed of hardened High Speed Steel. Long length Drill/Tap Bits tap up to 1/2" (12.7 mm) thick material. Split-tip drills fast and resists walking. Back tapered beyond tap to prevent thread damage. Quickly deburrs and counter sinks threaded hole. Fast, secure 1/4" Quick-Change hex shank. Quick-Change adapter included in Standard Length, Long Length, and Metric Drill/Tap Kits. For best results, use Greenlee cutting oil with all Drill/Tap bits.