Machine Design
Choosing Special Fasteners

Choosing Special Fasteners

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.

TAGS: Fasteners
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