When using locknuts, there are no special requirements […]
When using locknuts, there are no special requirements for bolts, as long as the bolts meet the national standards. The thread accuracy of the bolt must be 6g or above, and the tooth tip decarburization should be within the scope of the national standard.
Special note here: 6g thread precision and tooth tip decarburization are not special requirements beyond the national standard. Commonly used bolt national standards require 6g thread precision before surface treatment. Tooth tip decarburization is also required by the national mechanical performance standards. We emphasize these two points because:
a. If the thread diameter exceeds 6g or the tooth tip is decarbonized, after tightening, the anti-loosening performance of the anti-loosening nut will decrease, and it will be lost in severe cases.
b. Many bolt manufacturers and users only use thread ring gauges when inspecting threads. When the pass or stop inspection is qualified, the thread is deemed qualified. In fact, this is incomplete. Because the thread ring gauge only checks the pitch diameter of the thread, not the major diameter of the thread. Therefore, the inspection of the thread requires not only the through and stop ring gauge, but also the caliper (micrometer) to inspect the major diameter of the thread. Only the thread with pass and stop ring gauge inspection, and at the same time the large diameter inspection is also qualified, is a qualified thread.