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A guide to threaded rods

clock 10 minutes | 07 Feb 2022

Threaded rod in various sizes

A threaded rod is a type of fastener typically used to stabilise structures or some other object to a wall or ceiling. It’s also used when even the longest bolt or screw is too short for the job.

Threaded rod is known by several other names you should become familiar with:

  • Threaded stud
  • All thread
  • All-thread rod
  • Threaded bar
  • Screw rod

It’s threaded in a helical structure, like a long-threaded bolt or screw: The threading causes rotational movements during installation. The combination of rotational and linear movements generate resistance to pressure. You can screw nuts or bolts to it.

Threaded rod vs. bolt

If a threaded rod is similar to a bolt, what’s the difference? A rod is threaded on both ends, whereas a bolt has a head and is threaded on the other end. Size is another difference. Rods are usually long, whereas bolts are typically just a few inches long. That said, it’s possible to make a one-inch left-hand threaded rod simply by cutting a long-threaded rod down. Left-hand refers to the direction of the rotation. Threads can be either right-handed or left-handed – even both.

What are threaded rods used for?

Threaded rods pin or fasten two materials together. Their purpose is to withstand high levels of pressure and tension, though this depends on the threaded-rod material.

Threaded metal rods, which include titanium, zinc-plated steel and stainless steel, are used for heavy-duty applications. For example, a stainless-steel threaded rod or a threaded steel rod for that matter, is used in construction to join wood and metal together and stabilise structures. Copper threaded rod is malleable and ductile. With its high thermal and electrical conductivity, it’s a popular choice as a heat conductor and applications involving electricity, and as a building material.

Plumbing and contracting typically relies on threaded rods made of steel or stainless steel. They’re commonly used in HVAC installations, for example. They enable quick level or the sloping installation of ductwork, heaters, air handlers and other equipment. They’re also used to hang suspended ceilings and are ideal when proper alignment is needed in manufacturing and medical machines. You can even get hollow threaded brass rods, which are typically used in lampholders to feed wires.

Threaded rod application

At a glance: Materials

Nylon and metal rod uses vary, but are common in these areas:

Steel

Stainless steel

Titanium

Nylon

Brass

Copper

Aluminium

Construction, structural





Construction, non-structural




Plumbing & contracting



HVAC installation






Refrigeration installation


Metalworking (e.g., furniture)


Machinery




Aerospace


Marine



Ornamental/aesthetics




Automotive


Oil & gas



Military



Threaded rod can be made from a variety of materials, such as titanium and aluminium. Titanium is lightweight, resists corrosion and boasts high strength. Aluminium is very versatile with excellent corrosion resistance and good machinability.

Plastic threaded rods have gained in popularity, particularly nylon. It costs less than metals and is non-corrosive. In some non-structural applications, nylon threaded rods have replaced metal as the material of choice. It’s easy to cut to size and offers good insulating properties. The fact that it’s lightweight and resists vibration makes it ideal for the automotive industry.

Nylon threaded rod

Threaded rod colour code chart

You might notice that threaded rods are sometimes colour coded on one end. These codes are defined by the International Organization for Standardization (ISO) and recognised worldwide. White indicates the strongest rods. Red is the second strongest, made of 316L stainless steel, also called A4. Green is the third strongest, made of 304 stainless steel, or A2.


Property class

Material

Colour

4.8

Plain steel and zinc plated

None

4.8

ISO metric hot dip galvanised

Light blue

4.8

Oversized hot dip galvanised

Orange

8.8

Plain steel and zinc plated

Traffic yellow

8.8

ISO metric hot dip galvanised

Steel grey

8.8

Oversized hot dip galvanised

Purple

10.9

Plain steel

Oyster white

12.9

Plain steel

Traffic black

A2 (304)

Stainless steel A2

Traffic green

A4 (316L)

Stainless steel A4

Flame red


You can learn about stainless steels by checking out Understanding stainless-steel grades.

Types of threaded rods

The types of threaded rod include:

Fully threaded rod

The thread runs the entire length of the rod. These are the rods that typically secure structures to walls and ceilings.

Fully threaded rod

Double-sided threaded rod

This is a rod with threaded ends. The rod usually fits into an unthreaded hole and both threaded ends are fixed with nuts. These are commonly used in doors and assembly housings.

​Double-sided threaded rod

Internally threaded rod

Designed to mate with a threaded component. This not only ensures a secure joint but makes it easier to take apart if needed at a later date.

​Internally threaded rod

Tap-end studs

Similar to double-end threaded rods, but one end is longer than the other and requires a nut. The shorter side is the tap-end and has a chamfered point, which should be lubricated before screwing into a tapped hole. These are commonly used in the automotive industry and also have industrial applications on machines.

Tap-end studs

Hollow-inside threaded rod

The most commonly used rod in the lighting industry. The rod is hollow to allow cables and wires to pass through.

​Hollow-inside threaded rod

How to hang threaded rod from ceilings

Thread the rod into ceiling attachment points. You’ll need brackets under the installed piece, held in place with nuts threaded onto the vertical rod. These two components will help with the process:

  • Threaded rod hangers

Rod hangers are ceiling fixings for threaded rod, though some designs can also be used for walls. With less drilling, they’re also an easier alternative to wedge, or drop-in, anchors. They have a self-tapping concrete screw tip at one end with a threaded socket for the rod on the other end. Unlike wedge anchors, these threaded rod fixings can be drilled straight in, repositioned and installed closer to edges and in cracked concrete.

  • Threaded rod connectors

Threaded rod installation can involve connecting two rods together. Also called threaded rod end fittings, coupling nuts, and threaded rod end connectors, these are threaded internally, like a nut. In fact, metal rod couplers look like elongated nuts. One end of a threaded rod screws into the connector, or coupler, and the second rod screws into the other end.

How to cut threaded rod

Threaded rod cut to length must be done carefully, as it could affect the threads, especially if you’re using a hacksaw. You can cut threaded rod with bolt cutters or any tool really, but it’s best done with a rod cutter, as it’s specific to the job. If that’s not an investment you’re ready for, then follow these directions:

The best way to cut all thread rods is to first ensure you have what you need:

  • Bench vise or table clamp to hold rod
  • Two nuts
  • Angle grinder with a metal cut-off wheel
  • Sharpie pen
  • Safety goggles

Cutting threaded road to length:

  • Step 1 - Thread two nuts onto the rod past the spot where you plan to cut – allow a few inches
  • Step 2 - Tighten the nuts against each other
  • Step 3 - Mark where you want to cut
  • Step 4 - Cut against the shoulder – this will give you a clean, right-angled cut
  • Step 5 - Use the angle grinder to round off the edges – you can also use a file for this
  • Step 6 - Loosen and remove the nuts to clean and realign the threads

Threaded rod sizes

The key dimensions when ordering threaded rod are diameter, thread pitch and length.

The terminology used is the same as that used for screws, although there’s more information for screws. You can learn more in What are screw heads, drives and threads?

Threaded rod:

Threaded rod

Pitch: The distance from a point on the screw thread to the point on the next thread. You can identify the thread pitch using a pitch gauge. This is a simple matter of checking each form size on the gauge against the thread you’re identifying. When you have a match, the gauge tells you the pitch.

Thread angle: The distance between the sides of the thread. It tells us that both sides of the thread are angled to the same degree. Unified threads all have a 60° angle, as mentioned above.

Major and minor diameters: The major diameter is the rod’s largest diameter. The minor diameter is the thread’s lower extreme diameter.

Pitch diameter: Half the distance between the major and minor diameters.

When specifying a threaded rod

Use the nominal major diameter. The overall length is measured from one end to the other. The length can also be measured first thread to first thread.

Specifying a threaded rod

Thread count is measured in threads per inch (TPI). Inch-standard fasteners typically use thread count. Metric fasteners use thread pitch. Thread pitch is the distance from a point on the screw thread to a corresponding point on the next thread, which is measured parallel to the axis.

Thread pitch is usually measured in millimetres. The thread series determines the TPI and thread pitch. For standard fasteners, these series include Unified Coarse (UNC), Unified Fine (UNF), Metric coarse and Metric fine.

Threaded rod specifications first list the major diameter followed by the TPI or thread pitch. (Remember, inch-standard fasteners use TPI while metric fasteners use thread pitch.) A dash (-) usually separates the TPI or thread pitch from the major diameter.

For metric threads, an “x” – meaning “by” – commonly separates the thread pitch from the major diameter. Here are two examples of how to specify dimensions:

  • Standard: ¼" – 20 x 6'
  • Metric: M12 x 1.75 – 6g x 200mm

There isn’t one full threaded rod standard length. That is, metal rods come in standard lengths of 3-, 6-, 10-, and even 12 feet. Nylon rods are available in smaller sizes. We’ve put together this rod thread-size chart as an example of the range of metal sizes available, which vary by manufacturer. It is by no means exhaustive, but for illustrative purposes only.

Examples: U.S. Standard all thread size chart

Diameter (in)

TPI (in)

Length (ft)

1/4

20

3

5/16

18

6

3/8

16

10

7/16

14

12

1/2

13

3

1/2

13

10

9/16

18

3

5/8

10

12

3/4

10

3

3/4

10

6

7/8

9

12

7/8

14

3

1

8

6

1 1/8

7

10

1 1/4

7

6

1 3/8

6

3

1 1/2

6

10

1 3/4

5

6

2

4.5

12

6

32

3

12

24

3

Metric threaded rod table

Common metric sizes are below.

Thread size

Major diameter

Thread pitch (mm)

M3

3

0.5

M4

4

0.7

M5

5

0.8

M6

6

1

M8

8

1.25

M10

10

1.5

M12

12

1.75

M16

16

2

M20

20

2.5

Download free CADs and try before you buy

Free CADs are available for most solutions, which you can download. You can also request free samples to ensure the nylon threaded rod you’ve chosen are exactly what you need. You might find The ultimate guide to fasteners helpful. If you’re not quite sure which product will work best, our experts are always happy to advise you.

Whatever your requirements, you can depend on fast despatch. Request your free samples or download free CADs now.

Questions?

Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.

Threaded rod
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