Yes, they are for automatic balancing.

<a href=3D"https&#58;&#47;&#47;www.youtube.com&#47;watch&#63;v&#61;eq263AYg=
yYg" target=3D"_blank" class=3D"newlyinsertedlink">https&#58;&#47;&#47;www.=
youtube.com&#47;watch&#63;v&#61;eq263AYgyYg</a>

----------------------------------------
> Date: Fri, 6 Mar 2015 01:12:36 +0800
> Subject: [OT]: CD/DVD spindle boss has free moving bearings
> From: justin.richards@gmail.com
> To: piclist@mit.edu
>
> I have noticed that CD/DVD drives make noises when starting/stopping.
>
> I had assumed it was simply motor noise but never quite satisfied with th=
at.
>
> I have just dismantled the spindle boss(the bit the disk sits on then has
> the magnetic clamp to hold in place) and discovered there are about 10
> small bearing that are free to move about in a race and the source of the
> noise.
>
> I can only guess they are for balance.
>
> Anyone know how they work and if they are for balancing.
>
> Justin
> --
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