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Whether you're a seasoned contractor or a DIY enthusiast, you probably heard of threaded rods. Yet, not everyone's familiar with what threaded rods are and how they work or understands the different types and sizes associated with these types of industrial fasteners. This guide will provide a comprehensive overview of threaded rods, discussing everything from their basic anatomy to their various uses.

What Are Threaded Rods?

A threaded rod, also called a threaded bar or stud, is a metal rod with threading throughout its entire length. This type of metal fastener is typically made of carbon steel or stainless steel, with a black oxide or zinc-plated finish.

Their main characteristic (having threading all the way to both ends) is what separates them from typical bolts. Admittedly, both feature a very similar design, as they're both basically threaded fasteners. However, they're not the same.

Threaded bolts have threading on one end, while the other usually features a bolt head (commonly a hex head) used to drive the bolt. On the other hand, threaded rods have threading on both ends. The other significant difference is the shank length.

Bolts typically have shorter shank lengths measuring a couple of inches, while it's not uncommon for threaded rods to be a foot or even several feet long. By definition, threaded rods are long metal fasteners that have threading throughout their entire length, implying that both ends are threaded without any bolt head.

Different Types of Threaded Rods

There are three basic classifications of threaded rods: length, shape, and thread direction.

Length

Threaded rods are usually supplied in one-meter lengths (3.2 feet) or 3-foot segments at the larger diameter/thread sizes. Anything longer than that is basically made to order. These can be cut down to a specific length, either by cold cutting or abrasion. Threaded rods shorter than 12 inches are typically referred to as studs, regardless of their shape.

Shape

Threaded rods come in various shapes and sizes, and some shapes depend on the length of the threaded rod or stud.

Fully-threaded Rods

Fully-threaded rods, also referred to as all-thread rods (ATR), feature threading across the entire length of the rod. These typically have a uniform threading through the entire length, allowing full engagement of any mating fastener, such as a nut.

Tap-End Studs

Tap-end studs have a short thread length at one end that mates with the tapped machine hole. The other end, which often has a different thread pitch, is for engagement with other fasteners, such as nuts. They're available in both metric and imperial sizes.

Double-End Studs

Double-end stud bolts are threaded rods that have equal thread lengths at both ends with a gap in between. Unlike tap-ends, threading on both ends is of the same thread type and thread size, and it's typically designed to mate with a pairing nut.

Full-Bodied Studs

This is actually a subtype of tap-end and double-ends studs, and it refers to the correlation between the shank and thread diameter. Full-bodied studs are achieved by cutting the threads into the rod, which is why their shank is equal to the major diameter of the thread. Cutting disturbs the steel grain, so these aren't as strong as the following type.

Undercut Studs

Instead of cutting the threads into the rod, threading on the undercut studs is produced by rolling. This preserves the steel grain and even enhances its strength by a negligible margin, allowing for better distribution of axial stresses. However, since the material is rolled up to the major diameter, undercut threads often have the same diameter as the thread's pitch diameter.

Thread Direction

Thread direction refers to the direction in which the thread spirals, determining the direction of motion for tightening or loosening mating and pairing elements:

• Right-hand — Right-hand threads are configured in a way in which any clockwise rotation tightens the threaded rod to the fastener. This is the most commonly found thread on various machining elements.
• Left-hand — Configured in a way in which any counter-clockwise rotation tightens the rod to the fastener.
• Reversible — Reversible threaded bolts have a right-hand thread on one side and a left-hand thread on the other.

Materials

Material plays a crucial role in determining the tensile strength of the threaded rod. The most commonly used material is low-carbon steel and stainless steel. Stainless steel threaded rods are further divided into SAE 303, SAE 304, and SAE 316, depending on the application.

Additionally, other stainless steel grades are also used, such as ASTM A193 (Grade B7), ASTM A354 BD, and Grade 5. Other non-ferric materials include brass, aluminum, copper, and silicon bronze.

Tensile Strength

Tensile strength refers to the maximum stress a material can withstand before it breaks, and different rod materials and diameters have different tensile strength metrics. It's basically a maximum tension that can be applied to the rod before fastener fracture and failure occur.

These metrics are defined by the International Organization for Standardization, and each metric is assigned a color coding corresponding to specific tensile strength:

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

Finishes

Threaded rods come in a wide variety of finishes, depending on the base material. Since steel is the most commonly used material in threaded rod production, the most common finishes include black oxide, zinc-plating (chromate and dichromate), and hot dipped galvanized.

Applications

Threaded rods are a very versatile product that find uses across a wide variety of different industries, including construction (usually as anchor bolts), electrical, and agricultural industries. However, they're also used in the automotive, aerospace, and other types of manufacturing industries.

Stainless steel fully-threaded rods are particularly useful in all industries that require higher levels of hygiene, cleanliness, customization of appliances, and aesthetic appeal, such as medical, maintenance, and machinery industries.

Versatile All-Threaded Rods at Reid Supply

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