What are Threaded Rods?

1
What is a Threaded Rod?
A threaded rod, also known as a stud, is a
comparatively long rod that is threaded on both
ends the thread can extend along the complete
length of the rod. They are created to be used in
tension. Threaded rod in bar stock form is
generally called as all thread. Fully threaded
rods and fully threaded studs are the fasteners
with threads running their entire length for
full engagement of nuts or other the female
threaded components. Threaded rods, are also
known as all thread rod (ATR) or thread full
length rods (TFL), offer high grip strength and
evenly distributed tension when mounting and
securing components. These fasteners are
appropriate for use in a variety of general
purpose applications, including electrical,
plumbing, maintenance, and fabrication.
2
Types Threaded Rod
With respect to shape, stud bolts also known as
studs are categorised into three basic types
"fully threaded stud bolt", "tap end stud bolt",
and "double end stud bolt". Each of these studs
have different implementations. As the name
indicates, fully threaded studs have full body
coverage with threads for full engagement of the
matings nuts or similar parts. Tap end studs
have threads at the extreme ends of the body with
unequal thread engagement length, while the
double end stud bolts have equal thread length
at both the ends. Apart from these there are stud
bolt for flanges which are fully threaded studs
with the chamfered ends, and the double end studs
with reduced shank for special bolting
implementations. For the studs that are not
completely threaded, there are two types of
studs full-bodied studs, and undercut studs.
Full bodied studs have a shank which is equal to
the major diameter of the thread. Undercut studs
have a shank which is equal to the pitch diameter
of the screw thread.
3
Undercut studs are created to better distribute
axial stresses. In a full bodied stud the
stresses are greater in the threads than as
compared to the shank. Undercut studs or rolled
thread are also stronger because the metal is
"rolled" up to the major diameter, and not
removed. This maintains the grain of the steel,
and in some cases even improves it. Full bodied
studs or cut thread are weaker because metal is
removed to make the thread, disturbing the grain
of the steel. Undercut studs are only required in
implementations where the stud is exposed to
fatigue. Cut threads are entirely appropriate for
many implementations, even when rolled threads
may be slightly stronger. Mass produced
fasteners (standard bolts and studs) are
generally rolled, but jobbed parts with custom
features and the small lot sizes are likely to
be cut.
4
Strength
The approved tensile force for a non-undercut
threaded rod is defined by the American
Institute of Steel Construction (AISC) as
where d denotes the nominal diameter and Fu is
the resulting tensile strength of the material.
For undercut threaded rods the approved tensile
stress is described as
where ds denotes the diameter of the shank and Fy
is the yield strength of the material. Both the
equations give units of force for the result, for
example pounds force or newtons.
5
Class

• Metric threaded rods are marked on the end with a
  color code to describe the ISO strength class.
  The color codes are
• 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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