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Rules for Reusing Bolts

Question: Can a bolt be reused? If so, what grades and in what scenarios?

Answer: A bolt that has already been used in a given application may or may not be reused, depending on the grade, application, and recommendation of the “Engineer of Record”. There are a tremendous number of conflicting opinions on this subject, but the only definitive published information we can find on this issue from a reputable source is in regards to ASTM A325 and A490 structural bolts.

According to the Research Council on Structural Connections, Section 2.3.3:

“Reuse: ASTM A490 bolts and galvanized ASTM A325 bolts shall not be reused. When approved by the Engineer of Record, black ASTM A325 bolts are permitted to be reused. Touching up or re-tightening bolts that may have been loosened by the installation of adjacent bolts shall not be considered to be a reuse.”

“Pretensioned installation involves the inelastic elongation of the portion of the threaded length between the nut and the thread run-out. ASTM A490 bolts and galvanized ASTM A325 bolts possess sufficient ductility to undergo one pretensioned installation, but are not consistently ductile enough to undergo a second pretensioned installation. Black ASTM A325 bolts, however, possess sufficient ductility to undergo more than one pretensioned installation as suggested in the Guide (Kulak et al., 1987). As a simple rule of thumb, a black ASTM A325 bolt is suitable for reuse if the nut can be run up the threads by hand.”

When reusing bolts, it is critical to involve an engineer since the reuse of the fastener depends on a variety of factors including bolt type, application, grade, finish, installation method, etc. If the bolts have been tensioned beyond their yield point, they enter the “plastic zone” (where they elongate and do not contract once the load is removed), which means they may be subject to premature failure. Since it is virtually impossible to determine visually if a specific fastener has entered its plastic zone when previously used, the decision to reuse a fastener will be determined by the price to replace it versus the potential cost and/or liability of that fastener failing.

Spending a few hundred dollars replacing structural bolts supporting an overhead sign structure on the freeway makes sense when evaluating the potentially devastating consequences and liability involved in reusing bolts that may ultimately fail. On the other hand, attempting to reuse a few hundred dollars worth of bolts instead of replacing those fasteners on a noncritical pump or other piece of equipment might make sense when a failure would only result in the piece of equipment not working.

Posted by Anthony Porreco

Phone: (800) 599-6926 Email: anthony@portlandbolt.com
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The below content is submitted by readers and has not been researched or checked for accuracy. It is not endorsed in any way by Portland Bolt.

2 Responses to “Rules for Reusing Bolts”

  1. Sarah Kemp says:

    @FredHolmes Unfortunately, we are unable to answer this question. Portland Bolt manufactures nonstandard construction fasteners to ASTM specifications. SAE graded bolts for automotive applications are beyond our area of expertise. Sorry we can’t help.

  2. Fred Homes says:

    Is head bolts included in this subject matter? I meant head bolts cannot be reused too? I am just a second hand user and the person where I bought my car gives me a set of head bolts. I don’t have any idea if this is reusable or not but your article made me confuse. The bolts look like good and still on a great shape and loctite is still visible on all the bolts. So I want to know if I can reuse them or not?

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