Difference between revisions of "Threaded Fasteners"
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Revision as of 16:07, 2 June 2020
Threaded fasteners used in FS are most typically made of steel but are sometimes also made of stainless, titanium, or aluminum.
Contents
Standards
There are two main threaded fastener standards: metric and inch. Within these two categories lay additional standards set by various organisations. These standards may are often intercompatible but can differ in head size, strength, alloy, coating, pitch, and local avaliability.
Metric
Metric screws are listed in the following way:M6x25 x 1mm Class 8.8. The M6 referes to the major diameter being 6mm, 25: the shaft length is 25mm, and the pitch is 1 thread per 1mm. A class 8.8 bolt is a medium strength steel bolt with a tensile strength of about 800MPa and about 80% of that being the yield strength.
ISO
DIN
JIS
Inch
Inch screws are listed in the following way:1/4-20 x 1 Grade 5. The 1/4 is the major diameter of 1/4in, a thread pitch of 20 threads per inch, and a length of 1in. A grade 5 bolt is a medium strength steel bolt with a tensile strength of about _ksi and a yield strength of _ksi.
SAE
[grades, charts, etc...]
AN
Screw Types
| Photo | Names | Description |
|
Hex head | |
|
Twelve point | |
|
Socket head
Allen® head |
|
|
Shoulder screw | |
|
Set screw | |
| Quarter turn | A specialty fastener that allows quick installation and removal of body panels. |
Nut Types
Deez Nutz
Hex Nut
Weld Nut / Riv-Nut
Locknut
Locknuts resist loosening. Other methods can be used to resist loosening: lock washers, safety wire, locking adhesive, or design. Most locknuts are only designed to be installed a few times otherwise their loosening resistance is diminished.
| Photo | Common Name | Description |
| Jam nut | ||
| Nylon nut | ||
| Nylok | ||
| Distorted nut
Stover nut K-nut / Jet-nut |
Different components of the nut can be distorted to prevent loosening. For example: thread pitch and eccentricity. The temperature range is limited only by the parent metal or its plating and can be reused approximately 10 times before its locking capability is diminished[2]. A K-nut or Jet-nut is ideal for high temperature applications. | |
| Castle nut |
Threaded Insert
Fastener Characteristics (how to choose)
- Initial Tensioning
- Initial Tightening Force
- Brings bolt close to "proof load"
- Deformation of threads (pic)
- Maintenance schedule
Torque Tension Calcs
Further Reading
- NASA Fastener Design Manual
- Carroll Smith's Screw to Win
References
- ↑ https://en.wikipedia.org/wiki/Dzus_fastener
- ↑ Barrett, Richard. "Fastener Design Manual", Nasa Reference Publication 1228 (1990) pp7
