My motor came with a black ring attached to the bottom of the rotor. It spins along with the rotor, and it's not exactly a ring shape since it's open at one end - kind of like an omega symbol or like a stag beetle's horns. What is it called and what is it for?

black ring attached to the bottom of rotor


1 Answer 1


That is a circlip (or C-clip) - it looks like it is used here to prevent the shaft from coming out of the bearing.

From the Wikipedia link above:

A circlip (a portmanteau of "circle" and "clip"), also known as a C-clip, Seeger ring, snap ring or Jesus clip, is a type of fastener or retaining ring consisting of a semi-flexible metal ring with open ends which can be snapped into place, into a machined groove on a dowel pin or other part to permit rotation but to prevent lateral movement. There are two basic types: internal and external, referring to whether they are fitted into a bore or over a shaft. Circlips are often used to secure pinned connections.

  • $\begingroup$ Good thing I didn't go with my instinct and try to pry it off! $\endgroup$
    – Mark
    Aug 26, 2020 at 21:56
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    $\begingroup$ @Mark Oh yea! C-clips like those tend to pop off rather violently if you don't use the proper tool or let go of it while it's under tension. They are notorious for flying across the table/room and are hard to find on the floor. Also it's an excellent idea to wear safety glasses when using them because of the aforementioned flight risk. :) $\endgroup$
    – ifconfig
    Aug 27, 2020 at 5:49
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    $\begingroup$ If you ever need to remove one, do so inside a bag. It will ping off, but the bag will catch it before it disappears. They're cheap and it's worth having spares anyway. $\endgroup$ Aug 27, 2020 at 9:50
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    $\begingroup$ Some circlips are not meant to be re-used, and if you remove them, you replace with a new one. $\endgroup$ Aug 27, 2020 at 13:34

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