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

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.

Written ,


    ASME PCC-1 2019 paragraph 4(c)(1) states that: “when using bolts and nuts of common grade as fasteners, the use of new bolts and nuts up to M30 (1-1/8 inch) diameter is recommended when bolt load-control methods such as torque or tension are deemed necessary”

    This is a post-construction standard published by ASME and developed by post construction commmittee. This standard is not code, but it is recognized and generally accepted good engineering practice (RAGAGEP) meant for in-service inspection and maintenance of pressure equipment and pressure piping.

    More and more companies are insisting that RAGAGEP is used in lieu of code requirements, when it involves the safety, operation, operability, maintainability, and availability of your people and assets.

    @Hossein- Neither the AISC, ACI nor ASTM have any recommendations regarding anchor bolt reuse. With nothing published to reference, it would be left up to the project engineer.

    @Ammar- Torque values are tricky and inconsistent. For your specific application, the project engineer should be consulted to determine proper values.


    I have Grade 12.9 Nuts and Bolts on a flange, they are torqued up to 1000nM (within last 6 months)

    The Flange needs to be disconnected and reconnected, is it possible to reuse the Nuts?

    Thanks in advance

    @Shane- Unfortunately that is not something we are able to answer. The only published guideline we are aware of is the AISC guideline above, we do not have any information regarding the reuse of 12.9 graded fasteners.

    Shall I torquing the bolt again and again..and how many times would be permitted for torquing the same bolt .if possible again’ and again the torque would be 100 or less than of next time.

    @Bhanu- Reuse depends on the grade and how much the bolt has been tensioned to. We are unable to make recommendations for your application, you will need to check with the project engineer and let them determine if reuse is acceptable.

    In my project Gr8.8 bolt is getting used but recently we got Bolt with grade ASTM A325 in site and our consultant refused to accept for using A325 and the explanation was grade changes. Could you tell me whats the difference of these two grades

    @Sandeep- Grade 8.8 and A325 bolts are very similar in chemistry and mechanical properties, but they are not identical. They are also dimensionally different, the A325 has a larger head and shorter thread length. We would concur with your consultant that the bolts should not be substituted for each other unless the project engineer signs off on it.

    @Jeffrey- The guidelines we referenced in this FAQ were specific to structural bolts, and were published by the AISC, which handles structural steel. We are not aware of any similarly published guidelines for A193 B7 bolts.

    I have similar situation except I did not use TC bolts, but plain hex heads. I used 1 inch A490 and they were torqued to 475 for some temporary hold points. Can I reuse?

    @Nate- Per the AISC/RCSC guidelines, A490 bolts should not ever be re-used. However, if your project engineer has reviewed the variables and is willing to sign off on it, that would be up to them.


    I am currently working on a project in the Middle East and the structural steel is being fastened using tension control bolts (splined tip at the end of the bolt). The application uses both TC490 and ASTM F3125 bolts. The installer set the bolts to the designed torque when the splined tip sheared off. However, recently the need arose to loosen some of the hardware. The installer would like to reuse the bolts. My understanding is that once the splined tip on TC bolts is broken off that bolt has been tensioned to its plastic region and must not be reused. I would appreciate your thoughts on the matter. Thanks.

    @Adrian- The AISC/RCSC says that A490 bolts do not have sufficient ductility to undergo more than one pretension and shall not ever be reused. Additionally, because these are TC bolts (I assume button head), and the spline has already snapped off, that adds a layer of difficulty due to the fact that you will have a hard time holding the head still when re-tightening. I’d say that the safe bet is to scrap them and procure new bolts.

    We have some ASTM A193 Grade B8M stud bolts, diameter 1.1/4″ L=200mm, and applied a tightness as 650 N.m, that represent 10% more than specified (590 N.m). Can we reuse this studs?

    @Andre- We are not aware of any published guidelines that reference the reuse of stainless studs, so we’d have to leave that decision up to the project engineer. If the studs have been elongated or deformed, they for sure should not be reused, but in the absence of visible damage, it is a judgement call.

    Can We perform Bolt torque (100%) more than once at construction for 4″ gate valve installation?

    @Ishad- Once a bolt is torqued to 100%, it should not be reused unless the engineer make an allowance for it. Galvanized A325s and plain A490 bolts should never be reused, plain A325 bolts can be reused at the discretion of the project engineer.

    @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.

    @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.

    @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.

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