Irwin 80230 Hanson 1/4"-20 NC Thread HCS Plug Tap and 13/64" HSS Drill Bit Combo Pack 1/4"-20NC Tap size / # 7 Drill Bit Designed for hand threading work in a variety of materials Tap size and drill bit size are etched on each tool for easy identification First 3 to 5 threads chamfered for general purpose threading Straight flutes are ground to provide rapid chip removal for efficient threading