Quarter Turn - PA-3500 Line

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Captive quarter-turn stud assemblies with multiple hole receptacle rails.

PA-3500 Product Picture

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  • Type 3506-SC stud assemblies consist of a stud and coil spring captive in a steel cup. The assemblies are installed by flaring the end of the cup neck into a countersunk panel hole. Stud locking action compresses the spring, exerting a clamping force on the fastened parts. In locking, the stud spiral cam engages a rigid wire which is offered by the receptacle. MIL-F-25173A* approved.
  • Type 3522-S stud assemblies provide a nearly solid lock without allowing the sheet separation that occurs with 3506-SC assemblies while under tensile overload sufficient to overcome the expansion force of their springs. With 3522-S assemblies, the stud cam first quarter-turns onto the receptacle wire under spring tension supplied by a curved washer. Further locking rotation then starts to turn the cammed fastener head around a stud cross-pin. The head is moved downward as it turns, compressing a coil spring which is stronger than the curved washer, and finally compressing the curved washer flat. At the fully-locked position, the assembly has no remaining spring movement achievable by tensile overload. 3522-S assemblies are not MIL-F-25173A approved.
    CAUTION: Any external factor that prevents the stud from turning with initial locking torque could allow the fastener head to rotate first. This could convey an erroneous impression of locking while the stud cam has not locked onto the receptacle wire. All operators of this special purpose fastener should be trained to recognize proper stud cam locking.
  • Standard receptacles The PA-3500 Line receptacles come in both single hole and strip configurations. The strip configuration acts as a supporting frame for the panels or removable parts to be fastened, with continuous holes for stud engagement and rivet mounting on 3/8" centers. The strip is riveted to a support member and the stud panel rests against the strip face having the stud holes. The strips are aluminum alloy with a continuous rigid stainless steel wire staked across the underside of the stud holes. The fastened panel rests on the strip and its captive quarter-turn studs engage the rigid wire.
    Custom cut lengths of 3590 and 3595 strips may be specially ordered. The part callout system for cut lengths assumes standard hole spacing and location of the holes at each end at the standard distance from the end.

* Meets the design, physical and performance requirements of MIL-F-25173A. However, full mechanical properties testing may not be performed on each production lot.