Removing Threadlocked Screws With A Soldering Iron

A soldering iron applied to a stuck threadlocked screw in a titanium pen

We’ve all been there – that last stubborn screw, the one thing between you and some real progress on a repair or restoration. It’s stuck tight with thread-locking fluid, and using more torque threatens to strip the head. Frustration mounting, drilling that sucker out is starting to seem pretty tempting. But wait! [Daniel] offers a potential solution using nothing but a soldering iron.

This tool hack is pretty simple, but all the great ones tend to be straightforward. In the video, [Daniel] is faced with a titanium Torx screw that refuses to come loose due to threadlocker, an adhesive that is applied to screws and other fasteners to prevent them coming loose. Available in a variety of strengths, thread-locking fluid is great at keeping screws where they need to be, but too much (or the wrong kind) can seize a screw permanently.

Instead of drilling out the offending screw, [Daniel] reaches for his soldering iron. By applying a significant amount of heat to the screw head, the adhesive starts to give. After heating, working the screw back and forth breaks the threadlocker, thus freeing the screw. The whole process takes just a couple of minutes, and potentially saves the repairer from destroying a screw.

The chemistry behind thermoset adhesives makes for some great bedtime reading, however the main takeaway is that threadlock fluid, while somewhat resistant to heat, will eventually become brittle enough for the screw to come loose. Unlike most adhesives, which melt under high temperature (think glue sticks), thermoset materials tend to initially harden with the application of heat, before turning brittle and breaking. While high-temperature threadlocker derivatives exist, typical Loctite-branded threadlocker (and similar products) would not appear to be able to stand the heat of a typical soldering iron.

This soldering iron hack isn’t the first we’ve featured on Hackaday – check out this method on removing enamel from magnet wire. If you’re not too squeamish, also check out our thoughts on soldering iron cauterization.

27 thoughts on “Removing Threadlocked Screws With A Soldering Iron

  1. Never thought to use a soldering iron, but regularly use heat. It is, after all, in the documentation. Many types are also quite susceptible to solvents, and common thread fits being at least a tad loose, solvents can, with time, get in.

    Bearing retainer, on the other hand, gets hinkey. Heat is often not applicable if the bearing needs to be preserved, as there may not be clearance for solvents to get in.

    1. Freeze the bearing with dry ice while keeping the part around it as hot as possible.
      Though seals often don’t like that.
      Thankfully bearings are pretty much standardized nowadays, and manufacturers often have web tools or catalogues dedicated to finding a replacement for a busted bearing.

        1. A horse is a horse, of course, of course

          And a tool is a tool, so it’s cool, it’s cool

          I would not use a good tip for punching plastic, but many manufacturers (weller, for instance) supply acessories for plastic welding, wood burning, and other activities unrelated to electrical connection using molten, low temperature alloys.

          For shrink tube, I use whatever heat source is to hand, including an oxy-acetylene torch and the hot end of a welding rod right after breaking an arc. Not optimal, but sometimes, when it’s time to railroad, you gotta horsecart

          1. (I have used a handheld clothes iron held in a vise as a hotplate in the lab, and use a ceramic hotplate from the same lab to press a shirt before an important presentation, back when I wore a tie. And have done vacuum tight seals with gallium on a hotplate, because the proper heating setup wasn’t available. I have no shame)

          2. I’ve used and at times still use a bread toaster to shrink heatshrink tubing. I find it most useful when puting tube over the 1/4″ plug and a few inches up the cable when repairing guitar cables. In my experience using a (too) small heatgun for this task often makes wrinkles in the tube, especially when using cheap no-brand tubing of eastern origin.

            Raychem DR-25 FTW!

  2. Most loctite branded stuff is designed to give up at about 180C iirc. its in the data sheets. a heat gun works just as well, just don’t make a mess of your nice carbon fibre by over heating it if the bolt through its stuck!

    1. Exactly what I wanted to say. It’s usually in the design of the threadlock to soften, or become brittle and breakable, with heat. I always use heat to soften the threadlock, when I’m working on a motorcycle.

      For some threadlockers, you can get special solvents. Never used that, and I wonder if it’s really possible for a solvent to get in between the threads. Applying heat works great.

      Never thought about using a soldering iron though. But I guess they get hot enough. Should be over 280 degrees Celcius to soften the thread lock (or make it brittle, I don’t know which it actually is, only interested in that it works to release the bolt ;)).

  3. Mate of mine showed me this trick when helping me swap out the grips on my motorcycle for heated ones. The bar-end bolts have a load of thread locker on them, he pulled out a soldering iron and said “Hold this here for a few minutes” with it inserted into the end of the screw. Worked a treat!

  4. MIG weld a nut on for the larger stuff. Just stack a nut on top of the bolt and weld it to the bolt. The heat will break almost anything free below. Very useful trick for stuck car studs or HD stuff.

  5. Using heat to kill anaerobic adhesives is not new except perhaps to the electronics world. For over 50 years I’ve been applying heat, generally from a torch of some kind, propane or oxy-acetylene turned down, to kill Loc-Tite on fasteners on race cars. Like flywheel bolts. For over 50 years. That’s also how you kill the “industrial adhesive” (generally but not always some kind of epoxy) used in riveted and bonded or just bonded aircraft and race car structures.

    For small fasteners in delicate applications like a screw in a hard disk chassis this is a wizard idea. Kudos. I’ve always been able to break them loose with a tool that fits really well and the really close fit is crucial. You can also use chemicals carefully applied in a very limited fashion, like with a q-tip or syringe or whatever (so as not to contaminate anything else). Like the various penetrating oils. Anything that will attack the adhesive.

  6. Blue is still considered permanent for small fasteners: the breaking torque may be higher than the head or fastener can tolerate! Loctite puts the cutoff where you switch to purple at 6 mm, but practically speaking it’s more like 3 mm for most materials / fastener heads.

  7. Threadlock compounds aren’t thermoset, though, are they? I thought the vast vast majority were some sort of self-polymerizing methacrylate compounds, a closer cousin to things like superglue and perspex.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.