Kreg LH-DKDB 3/8-Inch Left-Hand Step Drill Bit for DK3100 Pocket Hole Machine This heavy duty cobalt steel drill bit is uniquely designed for use with the high-production Pocket-Hole Machines This product is easy to use easy to install and highly durable This bit features an exclusive left-hand thread designed for the center spindle of a DK 3100 only (H6828) For use in Kreg's DK3100 Pocket Hole Machine only. Simple, one-piece design. Made form cobalt steel for longer life. Drill pocket and pilot hole in one stroke. Produces a clean pocket hole that can be plugged.