1/2"-14 NPS Round Pipe Die, 1-1/2" Outside Diameter - High Speed Steel - National Pipe Straight Size: 1/2-14 National Straight Pipe Outside Diameter of Die: 1-1/2" High Speed Steel Round Split Adjustable Die Approximate Thread Diameter: .840" For OD threading standard "1/2" Pipe" - the actual thread dimension is greater than 1/2".