Shoulder Bolt :Things You Never Know

Shoulder bolts are frequently used in three-plate molds and stripper-plate molds.It hasthree main sections: the head, the shoulder, and the thread.

Shoulder bolts are available in both standard and precision grades. The diameter of the shoulder of a standard shoulder bolt is typically 0.002 to 0.004 in. smaller than its nominal value. Precision-grade shoulder bolts are only 0.001 or 0.002 in. smaller. Precision-grade shoulder bolts are typically used in applications where the shoulder acts as a shaft for a sliding or rotating component, such as a bushing or bearing. In these instances, the shoulder is referred to as a journal.

The tolerance on the length of the shoulder is typically ±0.005 in.If the length of the shoulders varies by a significant amount, any plate in contact with the bolts can cock and possibly bind. The more likely scenario is that the head of the shortest bolt will break prematurely due to uneven load.

Most manufacturers include a slight reduction in diameter directly under the head. This is called the shoulder neck.All manufacturers include a slight reduction in diameter at the end of the threads where they meet the shoulder. This is called the thread neck. It is necessary for manufacturing and lets the shoulder seat flush against its mating component.

The thread neck is the weakest point of a shoulder bolt because it has the smallest diameter. Properly torquing a shoulder bolt is very important. When you torque a bolt, it stretches like a spring. This spring-like tension reduces the chances of a bolt coming lose due to external forces such as impact and vibration.