Many fasteners are designed for special functional or material requirements.
Design factors to consider when choosing specialty fasteners include:
Communication: Early supplier input will guarantee sufficient lead time to design the fastener, conduct tests, and make necessary alterations.
Underengineering: A purchase should not be made solely on price. The fastener may be improper for the particular application or too frail for the job. Do not specify a single-thread fastener where a multiple thread is necessary. Do not use an existing fastener for an application that requires a specially designed fastener.
Overengineering: Do not request metal that is too heavy for an application, critical tolerances where they are not needed, or oversized nut-and-bolt combinations.
Finish: Choose finish after the supplier studies the problem. Finish hardness should be based on application.
Material: Match the grade of steel to the application. Be particularly aware of gauge thickness.
Fastener function: Clearly specify what the fastener will do when ordering. Be aware of fastener limitations.
Servicing: Before ordering, know if the fastener will be removed. If so, determine how often it will be removed and if special tools will be required.
Assembly techniques: Be sure a requested fastener is compatible with existing automatic assembly equipment. But do not compromise fastener reliability for assembly speed.
Marketing: There may be delays when ordering fasteners made of hard-to-get materials. Order size must be evaluated carefully. Once an order is placed, some suppliers may not be able to handle high-quantity runs on short notice.