Fractional Tap, National Fine Thread, 9/16-In. x 18

9/16" x 18, national fine thread, fractional tap, carbon steel, ideal for routine maintenance, repair work & for rethreading where high accuracy & tolerance thread is not critical, straight flutes are ground to provide rapid chip removal for efficient threading, designed for hand threading work in a variety of materials taps produce a class 2b thread, use 33/64" drill bit.