Thermal Expansion Limits in Aerodynamic Thermoplastic Housing Design
Accommodate thermoplastic thermal expansion using kinematic sliding mounts and recessed lap joints to prevent out-of-plane buckling and boundary layer tripping.
Shoulder Fasteners
Meaning
Precision-engineered bolts or screws feature an unthreaded cylindrical section between the head and the threaded portion to provide a built-in pivot or spacer. Shoulder fasteners are commonly used in machinery to allow for the rotation of parts or to maintain a specific distance between components. The diameter of the unthreaded shoulder is held to a very tight tolerance to ensure a proper fit with the mating part.
Spatial Positioning
Alignment of moving parts depends on the accuracy of the shoulder diameter and length. When shoulder fasteners are installed, the shoulder itself acts as a bearing surface or a guide for a rotating wheel or lever. This design eliminates the need for separate bushings or spacers in many simple mechanical assemblies.
Transfer Load
Management of shear forces occurs through the thick unthreaded portion of the bolt rather than through the threads. This makes shoulder fasteners much stronger in applications where the parts are being pushed sideways against each other. The threads are only used to hold the fastener in place, while the shoulder carries the actual mechanical load.
Achievement Tolerance
Maintenance of a smooth motion in a joint requires a precise gap between the shoulder and the hole of the moving part. Because shoulder fasteners are often made from hardened steel, they provide a durable surface that resists wear over thousands of cycles. Specifications for these components include the concentricity of the shoulder to the threads to prevent binding during operation.