Threaded Rod Grades & Specifications

Threaded rod is classified by the American Society for Testing and Materials International by grade, material and strength. The Society of Automotive Engineers specification J429 defines all threaded rod by its configuration as an externally threaded fastener. Usually full or continuously threaded, threaded rod is a head-less bolt and is also known as a stud, all-thread and T-rod. Used mainly for construction, renovation, electrical, maintenance and automotive repair applications, threaded rod comes in a variety of lengths, diameters, right- and left-hand thread pitches, grades and materials. T-rod is available in U.S. and metric sizes and is commonly sold at hardware stores, fastener distributors and manufacturers.

The most common steel threaded rod, classified as ASTM A307, is Grade 2 threaded rod made from low carbon steel. The stronger and more heat resistant Grade 5 threaded rod is made of medium carbon steel quenched and tempered. It is classified as ASTM A449. ASTM A354 is the classification for Grade 8 threaded rod, made of high-strength steel quenched and tempered. For proof load, yield and tensile strength values for threaded rod refer online to the ASTM, SAE and ISO mechanical requirements for steel fasteners chart or the Industrial Fastener Institute website and handbook, which can be found in Resources.

ASTM A193 Grade B7 is the specification for high strength, heat resistant American Iron and Steel Institute (AISI) 4140 alloy steel threaded rod. The versatile B7 threaded rod is in high demand because of its high strength, excellent heat resistance and resistance to corrosion. B7 is widely used in commercial plant applications and new construction projects for pipe and machinery installation and maintenance. Refer to the Industrial Fastener Institute and SAE handbooks online, which can be found in Resources, or in hard copy concerning other high strength alloy grades of threaded rod such as ASTM A193 Grade B16, Grade B7M and A320 Grade L7.

ASTM A193 Grade B8 (304 stainless steel) and grade B8M (316 stainless steel) are the two most widely used threaded rod stainless steel grades. Stainless steel threaded rod is used in high-temperature and high-corrosive environments such as chemical plants and refineries. Besides B8 and B8M, there are several ASTM specified stainless steel grades of threaded rod. By checking the ASTM, SAE and Industrial Fastener Institute reference information online, which can be found in Resources, or in hard copy, an engineer can find the right stainless steel grade of threaded rod for any application.

Threaded rod is available in metric grades as well. The International Organization for Standards (ISO) classification R898 includes low and medium carbon steel quenched and tempered class 4.6 and class 5.8, threaded rod similar to U.S. Grades 2 and 5. Class 8.8 and10.9 are classified as alloy steel quenched and tempered and are similar to U.S. Grades 8 and B7. Stainless steel threaded rod is also available in A2 and A4 stainless steel, which are the same as U.S. 304 and 316 stainless steels respectively. Metric threaded rods are marked on the rod tips with a color code. Class 4.6 is unmarked, class 8.8 is yellow, A2 stainless is green and A4 is red.

Threaded rod is manufactured in almost all ferrous and nonferrous metals as well as materials such as plastic and nylon. The ASTM and SAE have material specifications for the following nonferrous threaded rod material: aluminum, brass, copper, silicon bronze, monel and a host of exotic nickel alloys such as hastelloy and inconel. Material specifications, classes and grades are found on the ASTM,SAE, ISO and IFI websites, which can be found in Resources, and handbooks.