What are Dzus Fasterners?
Dzus fasteners are quarter-turn, self-locking panel fasteners made from heat-treated, cadmium plated nickel steel, used together with aluminum grommets and music wire springs. The system gives a secure, repeatable clamp that can be locked or released with a simple quarter turn, which makes it ideal for covers, plates, cowlings, and other panels that need quick removal and replacement on aircraft and vehicles.
When a stud is worn, bent, or broken, it must be replaced to maintain proper clamp and vibration resistance. Light-duty installations usually only require swapping the stud itself, while heavy-duty styles often require replacing the retaining grommet as well so the panel continues to locate and support correctly.
Modern manufactured “Dzus type” hardware is often zinc plated rather than cad plated, but the basic stud / grommet / spring system is the same.
Who invented Dzus Fasteners?
The Dzus quarter-turn fastener was invented by William Dzus in the 1930s, originally for aircraft applications where quick access and secure retention were both critical. As aviation technology spread, these fasteners were adopted in heavy machinery, race cars, motorsports bodywork, and a wide range of custom and restoration projects where panels are removed frequently.
How Dzus Fasteners are identified:
Each Dzus stud is identified by a type code, a size number, and a length, plus optional letters that describe special features.
For stud types and head styles:
In Dzus nomenclature, the leading letters tell you what the head looks like and how the stud behaves in the panel.
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Type A has an oval protruding head.
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Types F and FA have flush heads; FA adds a rounded edge while still sitting flush.
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Type HF has a hexagonal head for wrench operation rather than a screwdriver or Dzus key.
Additional letters modify those base types:
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J, as in AJ or FJ, indicates a longer undercut below the head so the stud can “eject” or sit proud of the panel when unlocked, making it easier to grip by hand.
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O, as in AO, indicates no undercut, which allows the stud to be fully removed from the panel when unlocked.
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W indicates a wing is attached to the head for tool-less operation; for example, FAW5-45 is a winged version of an FA5-45 stud.
For diameter and length:
The first number after the letters is the stud size family, which corresponds to its body diameter in sixteenths of an inch. A “5” size is a 5/16 inch diameter stud, a “4” is 1/4 inch, and so on. The number after the dash gives the nominal working length L of the stud in hundredths or thousandths of an inch, depending on the specific catalog series, and is what you match to your panel and spring stackup.
For springs:
Springs use the letter S, followed by a number showing which size stud they are paired with, then a dash and the nominal spring height. An S3-200 is a standard spring for a No. 3 stud, with a free height of 0.200 inches. Different spring heights in the same family allow installers to fine-tune clamp load as panel stacks vary.
For grommets:
Standard grommets are identified like springs, but with GA or GF prefixes that also indicate which stud head types they match. GA grommets are used with A and AJ studs, while GF grommets are used with F and FJ studs. A part like GA6.5-375 is a GA-type grommet for a 6.5 size A or AJ stud, with an overall length of 0.375 inches.
This coding system makes it possible to decode older drawings or airframe manuals and match them to modern stock, as long as you know the size family and required grip range.
Typical Dzus hardware types
In a complete Dzus installation you will usually see three components working together: the stud, the spring, and the grommet. The stud passes through the removable panel, the grommet supports and locates that panel, and the spring is mounted on the underlying structure where it reacts the load and provides the locking action when the stud is rotated.
Common combinations in vintage and restoration work include:
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Type A or AJ oval-head studs with GA grommets and S springs in light skins and access doors.
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Type F or FJ flush-head studs with GF grommets for cowlings and exterior panels that must stay flush with the airflow.
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Heavy-duty FA and HF styles in larger diameters where higher clamp loads or wrench operation are required.
Modern catalogs and suppliers also offer winged versions, captive grommet units, and special box-corner or side-mount springs that extend the original Dzus system into more complex panel geometries.
Dzus Hardware Visual reference
The following images represent thy typical Dzus hardware types. For more information on special Dzus hardware, please checkout the DZUS Quarter Turn Self Locking Fasteners Cataloge - 1944.
Type A Stud
Type F Stud
Type FA Stud
Winged Stud type AW
Winged Stud Type FAW
Winged Stud Type FW
Type GA Grommet
Type GF Grommet
Type S Spring
Type SB Spring
Type SB Dzus Spring
