Consider two stacked plates connected by some bolt, and the plates are supposed to be able to move independently.

Usually in such cases they are connected by rivets, and cannot be disassembled easily.

Is there a way to use a combination of bolts/washer/nuts instead?

I have tried these type of bolts with nuts inside:

enter image description here

but after only a few movements, the screw on the other end unscrews itself.

I think the issue is that after tightening, the bolt heads press hard on the plates, which is normal because you don't want play, but this also forces the screw to unscrew when moving the plates

  • 1
    Go to mcmaster-carr.com, look at the stuff in that catalog, get inspired. Feb 26, 2022 at 16:55

3 Answers 3


castellated nut image from Fastenerengineering.com

Better to involve bearings, but for a simple pivot on bolt with some washers as crude bearings, you just need a nut that won't unscrew. Meet the Castellated nut, (sometimes seen as Castle nut) and its friend the Cotter pin.

There is a hole through the bolt for the Cotter pin. The ends of the cotter pin are normally bent so it can't slip back out, not shown in this rendering. Sometimes there are two holes in the bolt (at right angles) which allows finer adjustment (1/12th of a turn to line up with one of the two holes rather than 1/6th of a turn for only a single hole.)

  • interesting, i've seen those type of nuts and didn't know what they are used for
    – Alex
    Feb 26, 2022 at 18:09

Or, instead of a castellated nut and the hassle of drilling the bolt for the cotter pin, there are two other possibilities:

  1. a nyloc nut - has a plastic insert which prevents rotation

  2. use two ordinary nuts, tightened against each other.


Sandwich some bearings in the stack.

If you can afford some gap between the plates, sandwich two bearings in there. One between the sheets, and one outside of "the moving" sheet. Now, the bolt will not feel any torsional force, as that will be interrupted by the bearings.

The only problem is the bearings cannot tolerate large compressive force (e.g. the way you tighten car axle bearings only slightly past bare contact, and certainly don't put any torque on it). So to keep the nut from walking off, you'll need a Nylok, jam nut or cotter, again just like a car wheel bearing.

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