DIY Skills: How to Loosen a Stuck Bolt With A Blowtorch

David in How To

3/21/17

[updated: 10/1/20]

This article may contain affiliate links, learn more.

We've all come across the stubborn bolt. You know the one. That bolt that needs come off, like, now, but for no visible reason, the nut won't turn. Turns out, there's a simple trick: add a bit heat and get it turning quick. Here's how I make it happen.

This year, ManMade is part of Bernzomatic's Torch Bearers program. We're sharing some our favortie creative projects and clever ways to use a blowtorch around the house. So, far we've shared we like lighting our grill with a blow torch , walked you through the basics of simple, safe pipe soldering, and built a simple DIY copper pourover coffee stand.

Why does this happen?

The problem with a rusted bolt is that the spaces between the threads get clogged with minerals and oxidized metal. Trying to turn the nut around these stuck joints can result in stripping, which transforms a simple task into a real pain in the … bolt.

That's where a bit of heat comes in handy. Metal expands slightly when heated, so warming up the nut a bit makes it ever-so-slightly larger, loosening the hold enough that it will be able to break free. It's important to keep in mind what you're heating here, make sure it's only the nut, if possible – or the female threads, and not the bolt's male threads.

Here are the steps:

Look around. We all get tunnel vision on these types of things, so it's easy to overlook things like paint or wires that might get ruined if they get heated up. Use a bit of heat shield or sheet metal if you need to protect something.

Prep the bolt. Use a wire brush to clean off the nut, and add some lubricant to help the process. A few squirts should do it; put it on and let it sit for about 15 minutes. Also, work in a well ventilated area or set up a fan to help flush out any gas from the heating process.

Think safe. You might be under a vehicle or in a tight spot, so always wear gloves, eyewear, and protective (non-flammable) clothing for your arms and neck if necessary.

Heat it up. Light up the torch and heat the bolt slowly, without getting the threads too warm in the process. It's not important to get them red-hot, just consistently warm around the outside. At this point, tap the bolt a few times with a hammer to help break it loose.

Unscrew and move along. For some extremely stuck bolts, it may take a few heat and tapping rounds to fully break it loose, but I've never had this method fail me.