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I have multiple components that use M2 size holes that I want to connect with each other, but without restricting the relative movement in one axis with each other. They are supposed to be connected using a parallelogram setup as shown in screenshot 1 and 2. Screenshots 3 and 4 show the mechanism extracted from a video (https://youtu.be/RYyMxo1lW9I?t=31)in a real life application (elevator sword).

My problem is that a screw and nut does not work because the relative motion to each other causes friction at the nut and it will get loose pretty fast. Ball bearings are an option but maybe there is a cheaper alternative. I am also awaiting the delivery of Locktite but I would love to have a better solution if there is one.

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  • Chicago bolts, rivets, etc.
    – user263983
    Jul 30, 2021 at 12:59

1 Answer 1

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If you're going to bolt this together (and I see no reason not to, so long as there is clearance for the fasteners):

  1. Don't tighten the bolts too much or it won't move.

  2. Use lock washers to ensure that the bolts don't loosen over time. There are a variety of lock-washer types, and there are also "nylock" nuts that have a nylon insert that works very effectively as a locking mechanism to ensure the nut doesn't back off the bolt. There are also castle nuts that are designed to tighten around the bolt, then a split pin is put through one pair of groves in the nut and through a hole in the bolt, preventing it from backing out.

  3. Often times, bushings are used when pieces must be tightly affixed, but still allowed to pivot. These are often used in automotive applications. Depending on the strength needed, you will have to make your bolts smaller to allow for the bushing to fit into the hole & the bolt through the bushing, or make the hole larger so the bush can accommodate the necessary bolt size and the hole accommodate the bush. The bushings can be plastic, brass or bronze - they all have their advantages and drawbacks, and it would be on you to research which would be the best for your purposes.

  4. Put some washers between the nut/work piece/bolt - these should allow the freedom for movement.

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  • Your choice of these methods should be based on how much movement, how frequent, how aggressive, the degree of monitoring and maintenance you will do, and the consequences of failure. Start with a locknut loosely applied. A simple washer, a combination of teflon washers, a friction bearing, a ball bearing, etc. Each progression gives you more ease of movement, more reliability, and more safety. Or perhaps less safety, if extreme ease of motion is not desired. Another thing: Ball bearings fully assembled cost less than a dollar. Is cost really a factor?
    – jay613
    Jul 30, 2021 at 14:38
  • This DIY project really just boils down to a self-made 3d printed model-elevator run with an arduino, so safety is not an issue here. Jul 30, 2021 at 14:48

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