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A threaded rod, also known as a stud, is a relatively long rod that is threaded on both ends; the thread may extend along the complete length of the rod. [1] They are designed to be used in tension. [2] Threaded rod in bar stock form is often called all-thread.

## Studs

Studs may have a drive slot in one end to facilitate installing the stud.

### Types

Undercut studs (rolled thread) are also stronger because the metal is "rolled" up to the major diameter, not removed. This preserves the grain of the steel, and in some cases even enhances it. Full bodied studs (cut thread) are weaker because metal is removed to create the thread, disturbing the grain of the steel. [4] [5]

Undercut studs are only required in applications where the stud is exposed to fatigue. Cut threads are entirely suitable for many applications, even when rolled threads might be slightly stronger. Mass-produced fasteners (standard bolts and studs) are usually rolled, but jobbed parts with custom features and small lot sizes are likely to be cut.

## Strength

The allowable tensile force for a non-undercut threaded rod is defined by the American Institute of Steel Construction (AISC) as: [6]

${\displaystyle P={\frac {0.33F_{u}\pi d^{2}}{4}}}$

where d is the nominal diameter and Fu is the ultimate tensile strength of the material. For undercut threaded rods the allowable tensile stress is defined as: [6]

${\displaystyle P={\frac {0.6F_{y}\pi d_{s}^{2}}{4}}}$

where ds is the diameter of the shank and Fy is the yield strength of the material.

Both equations give units of force for the result, i.e. pounds force or newtons.

## Class

Metric threaded rods are marked on the end with a color code to define the ISO strength class. The color codes are: [7]

• Unmarked — 4.6 class (tensile strength = 400 N/mm2, yield strength 240 N/mm2)
• Yellow — 8.8 class (800 N/mm2, 640 N/mm2)
• Green — A2 stainless steel (304)
• Red — A4 stainless steel (316)
• White — 10.9 class (1000 N/mm2, 900 N/mm2)

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ASTM A354 is an ASTM International standard that defines chemical and mechanical properties for alloy steel bolts, screws, studs, and other externally threaded fasteners. It is officially titled: Standard Specification for Quenched and Tempered Alloy Steel Bolts, Studs, and Other Externally Threaded Fasteners.

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## References

1. Soled, Julius (1957), Fasteners handbook, Reinhold Publishing, p. 90.
2. Speck, James A. (1997), Mechanical fastening, joining, and assembly, CRC Press, p. 54, ISBN   978-0-8247-9835-2.
3. Mavrigian, Mike (2008), High Performance Fasteners & Plumbing, Penguin Group, p. 49, ISBN   978-1-55788-523-4.
4. Machinery's Handbook (1996), pp. 1828–1830.
5. Machinery's Handbook (1996), pp. 1842.
6. Williams, Alan (2001), Structural Steel Design, 1, Kaplan AEC Engineering, p. 151, ISBN   978-1-58001-055-9.