L.H. Dottie DRT6C 6 Piece Drill and Tap Hex Bit Kit. The DRT6C is an assortment of six different drill & tap bits that are manufactured from High Speed M2 Steel. They are used to create screw threads or countersunk holes for easy connections and smooth finishes. Their 135 self-centering split point allow them to drill, tap, and deburr in one operation and are designed for use in up to 10 gauge metal.