The Hardware Man - Basics: Nuts & Bolts

Howdy folks,

One of the first big changes we made in the store when we bought the place was to reset and refresh our fastener section. Our relationships within the business pushed us towards Midwest Fastener and they were able to analyze what we had against what we needed and give us an organized and useful section that customers love. My wife, being a newbie to the industry, had a learning curve to get up to speed on SAE vs Metric, grade 2, grade 5, and grade 8, zinc or stainless, as well as all the other nuances regarding the humble bolt and nut. We move a lot of nuts and bolts as well as specialty fasteners. So, what makes this department so interesting?

In doing some historical reading the other day, I came across a topic that had national security implications and resulted in a law passed called the Fastener Quality Act in 1990 by President H.W. Bush. It was an expansion of another law; all focused on preserving the integrity of fasteners used in building and manufacturing against fraudulent and subpar imported materials. There had been issues with cheap materials being used in bridges, airplanes, and other critical infrastructure that did not perform to the required specifications. This act implemented standards and markings allowing quick reference of grades and traceability to the manufacturer.

Each bolt has distinct markings on the top indicating its grade or strength rating. While color may indicate the grade, that is not a hard and fast method. A grade 2 bolt has no markings on the top, is made of low or medium-carbon steel, and is rated for 60,000 psi tensile strength. Grade 5 bolts have 3 lines on the top, made of medium carbon steel that is tempered and rated up to 120,000 psi. Grade 8 bolts have 6 lines on the top of the bolt, made of tempered alloy steel and rated to 150,000 psi. Nuts follow the same general markings. Metric bolts have a number stamped on the top indicating similar strength ratings.

Shear strength also increases with a better grade of bolt, but the fastener should compress the pieces, allowing the friction of the parts to prevent breakage. However, in some situations, a grade 5 bolt will bend before breaking, while a grade 8 bolt should snap under the same pressure.

A properly installed nut should never be reused, as the threads will change pitch when torqued. That would explain why some nuts don’t go back on easily. It is better to buy new for the best fit and hold.

I realize this may be a bit more information than most of you ever wanted to know about nuts and bolts, and to the professionals, I hardly scratched the surface. However, the quality of fasteners is critical to the integrity of your product. So, whether it is a building or bridge being built or MAC-Bid finds, you need to assemble it’s good to know that standards are the same when buying from a vendor whose products are made in the USA.

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Daniel Karns and his wife own Clintonville Hardware & Rental along with other businesses. Join the discussion by contacting him at info@clintonvillehardware.com.