I am trying to find some type of mechanism where I can have a smooth but not too stiff rotation between two metal pieces. I was thinking of putting a shoulder screw through the pieces (the pieces will be side by side) and a nut at the end.

A real world example I can think of is how when you're unfolding a ladder, the part that unfolds has a joint where rotation occurs. It's smooth and stiff enough that you can let go midway and the ladder wouldn't collapse inward, but not too stiff that you have to apply so much force to unfold the ladder. What do they use to do that?


You have the right idea using a shoulder screw.

In between the two pieces, use flat washers and a springy Belleville washer.

A Belleville washer, also known as a coned-disc spring, conical spring washer, disc spring, Belleville spring or cupped spring washer, is a conical shell which can be loaded along its axis either statically or dynamically. A Belleville washer is a type of spring shaped like a washer. It is the frusto-conical shape that gives the washer its characteristic spring.

You can even stack them if needed.

They are available from McMaster-Carr.

  • $\begingroup$ Thanks. I'm definitely gonna read more into this this type of washer. Haven't heard of it. $\endgroup$ – juniorsworld Sep 22 '19 at 6:53

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