A guide to threaded rods

May. 06, 2024

A guide to threaded rods

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A threaded rod is a type of fastener typically used to stabilize 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: Key Differences

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 key 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.

Applications and Uses of Threaded Rods

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 instance, a stainless-steel threaded rod is used in construction to join wood and metal together and stabilize structures. Copper threaded rod is malleable and ductile, making it a popular choice in heat and electrical conductivity applications, and as a building material.

Plumbing and contracting typically rely on threaded rods made of steel or stainless steel. They’re commonly used in HVAC installations, enabling quick level or 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. Hollow threaded brass rods are also available, typically used in lampholders to feed wires.

Overview of Materials for Threaded Rods

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

Steel

Stainless steel

Titanium

Nylon

Brass

Copper

Aluminum

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 aluminum. Titanium is lightweight, resists corrosion and boasts high strength. Aluminum 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.

Threaded Rod Color Code Chart

You might notice that threaded rods are sometimes color-coded on one end. These codes are defined by the International Organization for Standardization (ISO) and recognized 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

Color

4.8

Plain steel and zinc plated

None

4.8

ISO metric hot dip galvanized

Light blue

4.8

Oversized hot dip galvanized

Orange

8.8

Plain steel and zinc plated

Traffic yellow

8.8

ISO metric hot dip galvanized

Steel gray

8.8

Oversized hot dip galvanized

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: A Comprehensive Review

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.

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.

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.

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.

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.

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 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: A Step-by-Step Guide

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 Rod 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

Dimensions and Sizing for Threaded Rods

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 micro pile threaded rebar for sale.

Threaded Rod Details:

Thread 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.

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Additional reading:
Pros and Cons Of Steel Frames

When Specifying a Threaded Rod

Tata Wiron - Steel Wire Manufacturers & Suppliers

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.

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 millimeters. 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

5/16

3/8

7/16

1/2

9/16

5/8

3/4