Flat Boring Bit 1-3/8″ x 6″ Bore small, clean holes at any angle in a variety of materials with the economical Milwaukee 1-3/8″ x 6″ Flat Boring Bit. This premium quality Flat Boring Bit is made of heat-treated high carbon steel, so the drill point and cutting edge can be resharpened for cost savings and long life. Bore clean, fast holes at any angle in wood, plastic, plywood and Formica. This bit offers a 6″ drilling depth but can be used with a 12″ extension (48-28-3350) for extended deep-hole drilling. 3/16″ shank diameter.