57/64" X 10-3/4 Taper Shank Oil Hole Drills. - .8906 Decimal Equivalent, 6-1/8 Flute Length. Taper Shank Oil Hole Drills are twist drills containing a hole that delivers coolant to the edges of the drill bit. Coolant greatly reduces chip packing by flushing chips out of the hole and lowering the heat. Bisco Tool Supply sells Taper Shank Oil Hole Drills perfect for deep hole drilling.