Taps/dies and Thread Repair
October 15, 2018
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In a previous post, I discussed tools to remove seized fasteners. Hopefully, by following a few of the tips in that article you were able to easily move past any sticky situations you found yourself in. If, despite your best efforts, you have now ended up with a buggered hole, I will discuss tool options and repair tips in this post.
Thread Repair – Have you have inadvertently bungled up the threads on a hole or fastener? Maybe you simply have some corrosion and debris you would like to remove from the threads? If you’ve found yourself in either one of these situations listed above, a thread restoration tool may be just what you need. Available in master kits containing both metric and SAE, these tools are designed to repair/restore damaged and stripped fastener threads. During use, these tools will also remove nicks, corrosion and burrs. Unlike taps, these do not cut new threads, but simply chase the existing threads. Made of hardened steel, they apply force in the correct direction causing the threads to conform to the original pitch.
Thread Files – These can be used on external threads when it is not necessarily convenient to use a die. This might be a situation where you are working with threaded rod, or a fastener that already has a nut on it. To use, simply find the correct file pitch for your particular thread type. During application, you will feel the teeth on the file positively engage the threads. As you draw the file across the threads, the file will force anything out of tolerance back where it belongs and re-establish the correct thread pitch.
The tools/methods listed above will serve you in most situations. Every once in awhile though you may run into a situation that you need it repaired exactly the way it was and things are past the point of repair. There are some options if this has happened to you:
Welding/Filling – If you have access to a welder, you can use it to carefully fill the hole with material and then re-tap to the original size. This doesn’t help with fastener/bolt threads, but then again you can more than likely buy a new fastener if needed.
Insert Repair Products – There are several companies that produce an insert allowing you to perform a repair that results in the original hole, thread type. To install, you simply drill a larger hole, tap it at the insert manufacturers recommended size, and screw in the insert. You select the insert based on the correct size/thread pitch needed. Once installed, you have an undamaged clone of exactly what you started with. These can even result in a stronger install, as the insert may be harder than the material being repaired. I have never needed or used these before, but it’s comforting to know that more options are available!
Heli-Coil – This is perhaps the best known version of a thread repair insert.
Keensert – Another populare thread repair insert. This insert has for keys that actually lock it into place
There are so many products out there to help today that you really have no reason to fear that stripped fastener so cast away those anxieties that come up when starting a new project. You can do it!