Designed for routing steel doors., titanium nitride (TiN) coating increases strength and durability. Tin coated router bits harden and protect the cutting edges in addition helps smooth the flutes for improved chip Ejection., #HSS1705TIN, (D) diameter: 1/2, (b) Cutting height: 2-1/2, (D) shank: 1/2, overall length (L): 5-1/2, Description: for norfield door machine, flutes: 1, HSS1705TIN High Speed steel (HSS) TiN coated 1/2 dia x 2-1/2 x 1/2 shank Single flute down-cut steel door Bit