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, plain finish 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. Plain 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 plain 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.
Nuts and washers can be reused??
@Daman- High strength structural nuts that have been fully tensioned should not be reused. Nuts that have not been fully tensioned are acceptable for reuse at the discretion of the project engineer. Washers can be reused provided they are not deformed from initial use.
What criteria and/or research is being used for the statement that high strength nuts that have been fully tensioned should not be reused?
@Todd- We do not have any published information regarding the reuse of nuts, just structural bolts. That said, based on the logic in this FAQ, nuts that have been fully tensioned may have been distorted or deformed due to the high tension. Additionally galvanized and waxed nuts will have the bulk of the wax come off during the initial installation, making reuse more difficult. Therefore, due to the low cost of the nut, we recommend to err on the side of caution and replace them.
sir we torqued new hsfg bolt in steel girder but due so.e mistake in length of girder we open the bolt can we reuse it
@Tanvir- ASTM guidelines allow for the reuse of plain steel A325 bolts at the discretion of the engineer. Reuse of galvanized A325 and A490 bolts is strictly prohibited. For other grades we are not certain.
Hello Dane,
Can you let me know about A325 Bolts for Derrick Base bolts Use log time?
@Simranpal- There are no specific parameters for use time on A325 bolts. In many applications they are used for decades. For your application, you should consult an engineer as vibration and fatigue can have adverse effects.
Thank you for sharing this information Mr. Porreco.
is it harmful for bolts and screw to torque it several times?
@Reza- It depends on the application. Some screw grades and applications allow for loosening and re-tightening, whereas others specifically prohibit the reuse of fasteners. You will have to consult with an engineer familiar with your application in order to determine that.
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?
@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.
I realize that I am responding to Fred Homes’ question several years after the fact, but if someone else like myself finds this it might help them.
Generally automotive manufacturers will stipulate in their technical service information wether or not bolts have been torqued to their yeild point. If the bolts have been torqued to yeild then they must be replaced.
If a bolt is reused you risk failure of the bolt when retorquing and the bolt will no longer provide the same clamping force as it did originally increasing the risk of leaks ect.