Quarter Turn Fasteners Information
Many situations demand quick removal of a panel to access equipment or controls. Examples abound in the following industries:
- machine tool
- off road
- heavy equipment
Quarter-turn fasteners present the capability of quick, but secure, assembly. Quarter-turn studs engage receptacles and are fastened by rotating the stud about 90°, also known as a "quarter-turn" rotation. Quarter-turn fasteners apply a predictable clamping force and provide a detent in locked position that resists accidental opening.
A quarter-turn fastener consists of a stud, retaining ring, and receptacle. A spring element is also required in the joint to allow them to work properly. The spring element can be part of the stud or the receptacle, depending on the fastener type. Quarter-turn fasteners connect components under a spring preload. As a result, unlike threaded fasteners, quarter-turn fasteners do not rely on the mechanical properties of joint and fastener materials to attain preload. The stud assembly, or receptacle, is designed with an internal spring component that allows repeated application of preload over a great number of repetitions.
When the stud rotates inside the receptacle, a cross pin rides up a cam causing a loading action to be applied. The complete motion is finished by rotating the stud 90°. Once the quarter turn is achieved, a positive mechanical stop is attained and the cross pin drops into the locking detent with the aid of a spring. It is the spring that provides locking force and resistance to vibration and fastener loosening.
Quarter-turn fastener heads can range from simple to a complex customization to fit the application. Possible interfaces include a winged design to allow tool-free installation and removal or a knob with an arrow indicating whether the fastener is fully engaged. The simplest designs use a slotted or Phillips-head recessed for use with standard screwdrivers.
Quarter-turn fastener benefits over other fastening methods include vibration resistance facilitated by the spring compliance built into most quarter-turn designs. This spring action also creates positive faster locking against vibration. Quarter-turn systems can be designed to address multiple material specification requirements while keeping the user interaction consistent and intuitive. This design flexibility allows for a multitude of options in actuation, ejection, stud and receptacle styles, retention, and trim.
Savings in cost and assembly time can be realized through use of snap-in, adhesive-mount, and clip-on components for initial assembly. Key though, is the reduction in service time for multiple disassembles and reassembles over equipment lifetimes. The simple, self-aligning assembly action requiring minimal tools makes quarter-turn fastening an industrial engineered, ergonomic solution for panel and cover attachment.
The quick opening and closing action of quarter-turn fasteners makes them ideal for applications where fast and frequent access is required:
- inspection panels
- access panels
- motor covers
Unlike conventional nuts and bolts, a quarter turn is all that is needed to release a cover and allow access. The self-locking feature of quarter-turn fasteners is very strong as testified by use in the aircraft and heavy equipment industries. Today, quarter-turn fasteners have been the standard for many fastening applications and, when possible, should be put to good use.