What is the Unified National Coarse thread pitch for a 1-5/8” diameter bolt?
Currently, the American Society of Mechanical Engineers (ASME) specification B 1.1 does not define a “standard” Unified National Coarse (UNC) thread pitch for 1-5/8” diameter bolts (or 1-7/8” for that matter). The “pseudo standard” coarse thread that is often used in the industry is 5-1/2 threads per inch. The 8UN (eight threads per inch) series is also frequently used for 1-5/8” diameter as it is the only truly defined thread pitch for that diameter. We believe the Industrial Fastener Institute is currently working on formally establishing Unified National Coarse thread standards for both 1-5/8” and 1-7/8” diameters. We’ll keep you informed of any developments in this area.
For a complete list of Unified National Coarse (UNC), Unified National Fine (UNF) and 8UN (eight threads per inch) thread pitches, see our comprehensive Thread Pitch Chart.