ORIGINAL: jigeye
1. Concerning mounting servos: I've read you should drill 1/16 holes, put in the metal grommets, then insert screws. What purpose do the little metal grommets serve? Can you do without them?
To followup on what suthep wrote . . .
The rubber grommets are vibration isolators. Properly installed they should have a specific amount of compression - no compression means the servo is loose, excess compression means that the grommet is no longer resilient and will transmitt vibration from the mount to the servo.
The function of the brass sleeve is to set the amount of grommet compression. With the flange (wide) part bearing against the servo mount, when the screw is run in and bottomed on the tube end of the sleeve, the sleeve prevents the screw pulling down on the grommet any further and thus sets the amount of grommet compression.
If installed upside-down, i.e. with the tube end of the sleeve against the servo mount (wood, ususally) and the flange on top of the grommet, the mechanical advantage of the screw threads will allow the screw to shove the tube end of the sleeve into the servo mount, effectively shortening the sleeve length and allowing the grommet to be overcompressed by the screw.
[engineering lecture mode off]