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The threads made by the tapper used for helicoil is not going to work with the standard size bolts. The taps used are specific STI (Screw Thread Insert) tools. But of course, if you decide the old thread is not too damaged you can use a standard tap and try to fix it.


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Use a planetary gearset. Drive the center continuously at the speed you want to tap. Use a mutilated gear to drive the ring in the opposite direction intermittently and at a speed that will back the chuck up. The chuck runs with the pinion gears. There needs to be a dog clutch rigged to the mutilated gear to hold the ring gear fixed when not backing it up. ...


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Short and simple, if you want to use the same size fastener again, you have to use a helicoil. By drilling out the old thread with the new pilot hole you have made it larger thus the fastener size will go up unless a helicoil is used to take up that change in diameter. Further more, helicoils also prevent the threads from needing to be repaired in the future,...


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Why does the helicoil need to be inserted if you have already tapped the new threads into a hole? Can't you just put a bolt in once you've tapped new threads? Consider the case of an M5 x 0.8 tapped hole. The helicoil will need the same pitch (0.8 mm) with a larger diameter hole. Note that the M6 is a 1.0 mm pitch so even if the helicoil tap was the same ...


2

The nyloc nuts come to mind... but sealing well around a thread will be a challenge. But why not keep a piston on the end of the thread in a cylindrical bore so the piston seals well on the bore and it is driven with a screw thread? Or just use a classic crank mechanism.


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The best I can think of is a barrel-cam indexer mechanism. Figure 1. Image source: nolte-nc-kurventechnik. See the Motion index drive on YouTube for a better view with fewer cam followers. The animation in Figure 1 shows a helical barrel cam but there are many other options. For industrial indexers there is often a period of "dwell" put into the ...


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There are a few alternatives. You can use blind rivets to attach the pieces together. This has the downside that its not easy to separate the pieces later. But is generrally faster as you can skip threading phase Another alternative is a blind rivnut (many rivnuts need acces to both sides). This has the advantage of being able to disasemble the structure. An ...


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Screw threads and nuts have to be made with clearance between their sliding surfaces to allow them to rotate without getting jammed stuck. If you try to use the head end of a threaded rod as a piston, the liquid you are trying to pressurize will ooze back through the clearance space and leak away. As pointed out by Solar Mike, there are types of threads ...


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When you see the distribution of the load in a thread, it usually involves only the first few threads. That is easier to understand when you consider that the thread is under load. The load is gradually transferred to the plate through the bolts. The fact that the core of the bolt transfers that load, creates a small elongation/compression (enough to ...


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Rivnuts are great, until they aren't. Get one that doesn't have a good grip and spins when you want to remove the bolt and it's all over. Your idea of using 1/4-28 threads is a good one, especially in steel and especially with the backup of VHB tape. With sufficient VHB tape, you could almost get away with tape only, but the risk factor is high. One-eighth ...


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The simple answer is that using a helicoil allows you to repair a thread while keeping it the same size. Say you have an M8 thread which is completely stripped, you now have an approximately 8mm diameter hole. If you want to restore the original thread size you need some way to reduce the size of the hole again. You could just drill out the hole to the next ...


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Also consider that the damaged thread / hole has to be drilled out to allow the oversize helicoil to fit to provide the new thread.


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The plumber's strap wrench is a very practical tool for this job. Here is one for $ 15.30 from Amazon, just for illustration.


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What I read in the references is BSPT is tapered similar to NPS. Of course you still need pipe dope to fill the spiral leak path, so not good for very high pressures such as 1000 + psi. The BSPP requires a copper washer, known as a metal to metal seal in the trade. There are hundreds of patented tubular threads used for oil/gas well pipe with various sealing ...


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The product that Jonathan R Swift created for himself does exist in commercial form, for 10, 12 and 14mm spark plug threads. Can save having to Helicoil a head, including all the labor to pull it, etc. Sold by NAPA, Amazon, and others. https://www.napaonline.com/en/p/SER3689


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