Series E524 straight flute high speed steel, straight flute unified national fine thread hand tap sets is a versatile tool, suitable for hand and machine tapping. Features and Benefits 1.5 x D usable tool depth to diameter ratio for versatile threading in through or blind holes Unified national fine thread construction Straight flute taps Right hand rotation High speed steel tap with bright finish enhances tool durability and performance 2B tolerance guarantees precise and reliable thread fits Typical Applications Free machining Plain carbon steel Copper Copper alloys Suitable for tapping in blind or through-holes Standards ISO 529 - hand tap standard Sets include 1 of each tap: Taper, Second, and Plug