J-B Weld: What Is It & How Long Will It Last?

By thewriteDuffy •  Updated: 09/14/22 •  5 min read

While my husband and I are lucky enough to have many friends who do weld and are around if we have a big job, we’re not ones to go ahead and fire up a welder every time we have a small fix or something to bond.

And that’s where J-B Weld comes in. If you haven’t yet used this amazing DIY product, keep reading cause I’m certain you will love the J-B Weld Original as much as we do! It’s one of my favorite tiny tools!

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09/21/2022 03:32 am GMT

What is J-B Weld?

J-B Weld is basically an epoxy (or filler) which is chemically cures after mixing the epoxy resin (called the “steel” tube) and a hardliner.

According to J-B Weld the company, it was actually was developed as an alternative to traditional torch welding, and it can actually replace some small welding jobs.

Does J-B Weld Actually Work?

Yes, J-B Weld does actually work! But it’s not for every job, and definitely not a replacement for welding on all jobs.

In metal parts, JB-Weld is ideal for joining or filling holes. This allows JB Weld to do some jobs welding cannot. In contrast, JB Weld can be hard to use for certain welding jobs where the strength of a metal bond is really needed, such as joining two long metal pieces together at an angle.

On fiberglass, J-B Weld does a fantastic job of joining and filling gaps as well.

I’ve never tested it myself, but J-B Weld is also supposed to work on:

J-B Weld won’t work on:

How Long Does It Take for J-B Weld to Cure and Harden?

According to the package, J-B Weld should take about 15-24 hours to completely cure at room temperature, when mixed at the right ratio of 1:1.

From personal experience, J-B Weld stays pliable for about 30 minutes after you’ve mixed it and is set in about 4-6 hours enough to remove any clamps or ties you’re using.

With that said, they state that it takes 15-24 hours to fully set in room temperature for a good reason; things like temperature and humidity can affect this time at the extremes.

A good way to be sure is to set aside some of the excess mixed J-B Weld from your project and let it air dry in the same room as your project, under the same conditions. This will serve as a test splotch that you can poke at now and then to see if it’s dry, rather than poking at your project and potentially damaging the bond.

Once your text spot is completely dry and hardened, you can safely reasonably assume your project is dry as well.

Finally, when it doubt, and if the project is important, give it some more time.

Can You Remove J-B Weld After it’s Hardened?

Once it’s set, J-B Weld is not easy to remove, but apparently, it can be done.

According to the J-B Weld website, J-B Weld can be removed by grinding or filing it off, or by directly heating it above the 600º maximum temperature threshold.

How Strong is J-B Weld?

If you look in enough places, you can find some pretty specific strength data for J-B Weld. I’ve put it into a chart to show you how strong of a hold you can expect.

Important note: these strengths listed in the chart are for their older formula. According to their website and new packaging, J-B Weld now has a “Higher Strength Formula” and the tensile strength is listed as 5020 psi, which is higher than the original 3960 PSI you’ll see in the chart below (I couldn’t find the updated tests for the new formula).

Even though these PSI strengths are for the older formula, you can probably expect the gap between types of strength to be about the same.

How Long Will J-B Weld Last?

On the .com website, J-B Weld in the package is said to have a shelf life of only three years, but the twin tubes can last longer. While longer is pretty vague on the South Africa J-B Weld site, it claims that tubes of J-B Weld will last up to 25 years once open, as long as the caps are secured tightly between uses.

As far as how long it will last on your repair or project, that will depend on a number of factors like temperature, pressure, and movement.

That said, if used on a small, reasonable repair and that doesn’t experience extreme temperatures, pressure or movement, I can see J-B Weld lasting forever; there’s no reason for it not to.

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09/21/2022 03:32 am GMT

FAQ

Will J-B Weld Hold Up in the Cold?

As a Canadian, I can happily report that once cured, the Original J-B Weld formula is supposed to maintain its characteristics to temperatures as low as -55º C.

Is J-B Weld Permanent?

Yes! After mixing the two epoxy compounds together and curing it for 15-24 hours, J-B Weld forms a permanent bond and can be shaped, tapped, filed, sanded and drilled after curing.

What is the Strongest J-B Weld Product

J-B Weld actually makes a ton of products, but out of their twin tube epoxies, their Original formula and MarineWeld formulas are the strongest with both having a tensile strength of 5020 PSI.

thewriteDuffy

At home, April is a mom, wife, and DIY darling. Among other home projects, she helped her husband Dan renovate their 1986 bungalow and is currently designing and decorating the 2023 custom home they are building themselves. Professionally, April is a writer, author, and online marketer with 15 years of experience writing for newspapers and magazines, building online authority websites, and publishing books.