How to Measure NAS Bolts
National Aeronautical Standards (NAS) bolts are exclusive to aircraft construction. Due to federal regulations, measuring these types of bolts require an understanding of how the bolt is utilized. The smooth portion of the bolt, the area below the hex head leading down to the threads is the grip. The grip equals the thickness of material being held together. The diameter of the bolt must conform to strict engineering standards for shear strength in holding the materials. Grip length is measured in 1/6-inch increments. The bolt diameter is measured in 1/16-inch increments.