With a tensile strength of 3,960 psi, J-B Weld is a structural adhesive, meaning that it makes permanent repairs that are as strong as the material it bonds. Its ingredients include epoxy adhesive mixed with fine particles of iron and steel. J-B Weld consists of two parts; either part washes off your hands and tools easily. When cured, J-B Weld withstands temperatures of over 500 degrees Fahrenheit (300 degrees Celsius), making it a suitable material for repairing engines and other moving steel parts that generate heat. It isn't suitable, though, for super-hot applications, such as automobile exhausts.
Things You'll Need
- Acetone or lacquer thinner
- Utility knife
- Plastic spatula
Clean the surfaces you intend to bond thoroughly to remove grease and fine dust. The most effective way to do this is to wash the surfaces with a strong solvent, such as acetone or lacquer thinner.
Roughen the surfaces with sandpaper or by scoring them with a sharp knife. This increases the bond strength of the adhesive.
Deposit equal amounts of J-B Weld epoxy and hardener on a disposable sheet of cardboard. Mix them together with a thin plastic spatula or the tip of a utility knife blade. Stir thoroughly until the mixture is a uniform gray color.
Apply the epoxy to one of the surfaces being bonded and join the pieces. If you're patching a crack, fill the crack with the adhesive.
Clamp the pieces you are joining with clamps and leave them undisturbed for four to six hours. Similarly, if you filled a crack, leave it undisturbed for the same amount of time.
Allow the adhesive to cure for 24 hours before subjecting the repair to strain.
Tips & Warnings
- Heat helps the adhesive cure more quickly. If time is an issue, you can use J-B Weld KwikWeld. It sets in six minutes and cures in four to six hours, but its tensile strength is only 2,424 psi.
- J-B Weld bonds metal, ceramic and rigid plastics. It won't bond flexible materials, such as leather, vinyl, canvas or flexible plastics.