Self Aligning Tap & Drill Set, National Coarse, 5/16-In. x 18

5/16" x 18, national course, self aligning tap & drill set, performance threading system self aligns tap in pre drilled hole especially in irregular surfaces or through holes, carbon steel, ideal for routine maintenance, repair work & for rethreading, straight flutes are ground to provide rapid chip removal for efficient threading, designed for hand-threading work in a variety of materials, includes letter f drill bit