Threads, as crucial mechanical fastening components, are extensively utilized across various industries. Different types of threads exhibit significant differences in structure, characteristics, and applications. This article will delve into the distinctions among several commonly used thread standards: NPT, PT, G, ZG, RC, and M.
1.NPT threads, or National Pipe Threads, are a type of 60° tapered pipe thread widely used in North America. The key feature of NPT threads is their taper ratio of 1:16, meaning the diameter changes by 1/16 inch per inch of length. This design ensures a tight fit between the NPT threaded fitting and the pipe wall, delivering reliable sealing performance. NPT thread specifications are denoted in inches, with common markings such as 1/4, 1/2, and 1/8, which represent the nominal diameter of the thread.
2.PT thread, also known as the British Standard Pipe Taper thread, is a 55° tapered pipe thread with a 1:16 taper ratio. Characterized by its fine pitch and reduced thread crest/root height, PT threads feature a compact structure that significantly enhances sealing performance. With a 60° thread angle (Note: standard PT threads typically have a 55° included angle; this may refer to flank angle), this design withstands substantial axial pressure and delivers superior compressive strength.
3.G thread, classified under the 55° non-pressure-tight pipe thread category, belongs to the Whitworth thread family. Characterized by high international standardization, G threads feature unified parameters and symbolic notation, significantly reducing communication barriers and compatibility issues while enhancing operational efficiency. Their sizes are typically marked in inches (e.g., 1/4, 1/2, 1/8), representing the nominal diameter.
4.ZG thread, designated as a tapered pipe thread standard for pressure-tight joints, features a conical profile that creates progressively tighter compression during assembly, ensuring a reliable fluid-tight seal. Formerly denoted as ZG in China's obsolete mechanical drawing standards (GB/T 12716-1991), this specification has been superseded by ISO-compliant designations: R (external taper thread), R1/R2 (external thread variants), and RC (internal taper thread) per current GB/T 7306.1-2000.
5.RC thread, correctly defined as the internal taper thread under ISO 7-1 standards, is extensively utilized for pressure-tight piping connections. Characterized by its rounded thread profile (55° Whitworth form), RC threads distribute stress more uniformly than triangular threads while providing enhanced self-sealing capability. Its dimensions and specifications are governed by GB/T 7306.1-2000 (replacing obsolete GB/T 193-1981), which aligns with ISO 7-1 for metric pipe threads.
6.M thread, also known as Metric thread, is the standardized thread system predominantly used in China. Characterized by its 60° thread angle, M threads feature pitches (axial distance between adjacent thread crests) arranged in segmented arithmetic progressions per ISO 261 standards. Specifications are defined in millimeters and denoted as M[Nominal Major Diameter]×[Pitch], e.g., M10×1.5 indicates a 10mm major diameter with 1.5mm pitch.
If you have any enquiry about quotation or need details about our product please feel free to email us at sales@dljierui.com.
Thanks for your interest in our products.
