What is the difference between A194 grade 7 and grade 7L nuts?
A194 grade 7 nuts are commonly used nuts for both high temperature and low temperature applications, and is commonly paired with bolts made to either A193 or A320. When used in conjunction with A320 bolts in a low temperature application, or if specially requested, they are charpy tested to assure they will perform well in a low temperature environment. When that charpy test passes, the nuts are marked with an “L” to show that they have been tested. The same is true with A194 grade 4 and 4L nuts, although Grade 4 and 4L nuts are being withdrawn from the A194 standard by the ASTM committee due to lack of use and material availability.