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I'm trying to find the right joint for a small but sensitive application. The joint should be around 10mm-20mm long with a diameter/height of <10mm. Because of the high sensitivity (thus a need for a low friction joint), do ball joints or universal joints typically have lower friction?

I see that camera stabilisers tend to use universal joints - do universal joints tend to have lower friction then?

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    $\begingroup$ Can you supply some more information about the application and what kind of load will be on the joint? That will affect how much friction the joint creates, especially depending on your ability/desire to lubricate the joint. Also, a u-joint will transmit rotation while a ball joint won't, which is a pretty significant difference. $\endgroup$ – Trevor Archibald Apr 22 '16 at 14:31
  • $\begingroup$ @TrevorArchibald Sure. The load is about 100g-150g. I'm hoping to not having to lubricate the joint, but it could be lubricated if there's no other option. Rotation isn't supposed to be transmitted, so a bearing will need to go along with the u-joint if it is to be used. $\endgroup$ – John M. Apr 22 '16 at 14:45
  • $\begingroup$ Its possible to make a magnetic ball joint that has nearly no friction $\endgroup$ – joojaa Apr 23 '16 at 21:02
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It depends exactly what you want.

Ball joints and universal joints aren't directly comparable as universal joints can transmit torque (as in drive shafts) whereas ball joints just provide location.

There isn't an inherent difference in friction between the two as this will depend on manufacturing tolerances.

The big advantage of a ball and socket joint is that is can provide precise location of a pivot point but allow free movement in rotational axes. On the other hand a universal joint moves more freely in some planes than others as it is the combination of two axes of rotation.

It really depends whether you just want rotation about a fixed point (as in a tilt/pan mount for a camera) or transmission of axial torque (as in a drive shaft).

Often ball joints are designed with a moderate amount of friction just by being a tight fit, however there are are also spherical bearings which give rotation about a point in 3 axes and may give you more options.

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