1.5mm HSS Drill Bit Long Series Carded 2501-1.50S by Bordo

BLACK FINISH (also called blue finish) A black finish is achieved by steam tempering, a thermal process resulting in a porous tool coating. This surface helps to keep lubricant on the tool, particularly important on the cutting edges, thus reducing friction and cold welding. The result is increased tool life. Black finish tools are generally recommended for ferrous applications where the oxide layer aids chip flow and heat dissipation.