NPT NATIONAL PIPE TAPER BUTTON DIES

Sutton Tools National Pipe Taper (NPT) Button Dies are premium-quality threading tools engineered for cutting new external threads or chasing worn threads on imperial pipes and pipe fittings. Sutton manufactures these dies in a universal 2-inch Outside Diameter (OD), making them compatible with standard 2" adjustable die stock handles or guides.

• Thread Size: 1/8" NPT (National Pipe Taper). The "1/8 inch" designation refers to the nominal inside diameter of the pipe it threads, not the physical size of the die or the external pipe diameter.
• Pitch (TPI): 27 Threads Per Inch.
• Outside Diameter (OD): 2 inches (50.8 mm). This is a massive outer disc size relative to the tiny 1/8" cutting hole, requiring a standard 2" die stock handle.
• Thickness: Approx. 5/8 inch (15.8 mm), providing enough depth to handle the standard length of an NPT pipe engagement.
• Thread Taper: 1:16 taper ratio (0.75 inches per foot or ≈ 1.79° angle relative to the center axis). This taper ensures that as the male fitting is screwed into a female port, the threads wedge tightly together to create a seal.

• Composition: Made from high-carbon tool steel with a bright finish.
• Best Suited For: Thread cleaning (chasing), rust removal, and cutting new threads into soft materials like plastics, brass, copper, and aluminium. 
• Critical Limitation: Carbon steel lacks the red-hardness of High-Speed Steel (HSS). It should not be used to cut new threads on stainless steel or high-tensile carbon steel pipes, as it will dull or chip the teeth quickly.
• Application Warning: Per Sutton Tools' product documentation, carbon alloy dies are rated for general purpose / DIY use only and are not suitable for critical pressure, safety, or precision industrial pipework.

• Target Major Diameter (Pipe Outer Edge): The pipe end must have a starting outside diameter of roughly 0.405 inches (10.29 mm).
• Chamfer Requirement: Give the tip of the pipe a 30° to 45° bevel (chamfer) down to about 9.3 mm. Because NPT dies cut on a taper, they require a heavily beveled leading edge to help the first 27-TPI teeth bite into the material square.
• Hand Tapping Rotation: Turn the die 1/2 turn forward, then 1/4 turn backward to fracture and clear out metal chips from the internal waste flutes. Always use a dedicated thread cutting fluid (or soapy water for plastics) to protect the carbon edges.