I imagine this is an easy concept but I do not know much about mechanical engineering design.

I am trying to make a "knob" like a control knob in solidworks that turns and is locked in place after twisting. I am thinking of a twisting knob in a labyrinth game or something like a foosball table knob that is locked in place after turning, or just a general control knob on an oven. I want to figure out how to design the "interface" that lets the knob turn yet stay in place after turning but do not know enough vocabulary to point myself in the right direction. Does the "interface" I am looking for have a name? How does one go about making it?

  • 1
    $\begingroup$ Do you want to it lock at specific points during turning (like how a stove knob might click into high or off, but can also be moved to lower temperatures freely). Or do you mean you turn it where you want and then it stays there until you move it? $\endgroup$
    – JMac
    Commented Jan 12, 2017 at 2:20
  • $\begingroup$ I think the term you are looking for is indexed. $\endgroup$ Commented Jan 12, 2017 at 10:50
  • $\begingroup$ Common biological optical-microscopes' nose-piece ( turnstile like ) contains a clip-like thing on the resting part and a groove-like thing on the movable portion. They serve exact same purpose (as seems from the text by OP). However I don't know their technical names. $\endgroup$
    – user8831
    Commented Jan 12, 2017 at 13:38
  • $\begingroup$ @Jmac Either one would work for me. $\endgroup$ Commented Jan 12, 2017 at 14:58
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    $\begingroup$ @TryingToTry So do you just want a common control knob? I'm pretty sure the "interface" they use is just surface friction. There just needs to be two interfacing faces with enough surface area to hold the knob in place. You would just need to tighten it enough so it doesn't move on it's own but is loose enough to move when turned. I assume most knobs use friction; but that may not be true at all so this is only going to be a comment. $\endgroup$
    – JMac
    Commented Jan 12, 2017 at 16:50

1 Answer 1


A cogged positioning system uses the concept of a detent - a pin, ball, pawl or bump that fits against a mating cavity. Usually there is some kind of spring to allow the detent to disengage when enough force is applied. This gives the familiar click as a knob is rotated.

So to answer the question the interface is called a detent. Google search detent ball for examples of how a detent works.

Wiki definition here https://en.wikipedia.org/wiki/Detent


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