IRWIN 1904P 3/8-18 NPT High Carbon Steel Pipe Tap High carbon steel pipe taps are ideal for pipe fittings, cutting internal threads and wherever an extremely tight fit is required. Taper taps have 8 to 10 threads chamfered for easy starts in tough materials. Four flute design on all taps ensures fast and easy chip clearance. Required drill size is permanently etched on the tool for quick and easy reference.