What does a star nut do?
 

I know it may sound stupid but i've just bought a bike frame to do up and I'm abit new to it all so bare with me.

On front forks, the fork goes up through the head tube which has a headset fitted and the stem clamps on to the steerer tube. i've heard people on ebay mention that a star nut is fitted. Whats this all about?

Please could anyone shed any light on it?

Many Thanks Gaz.

On threaded headsets, you use the threading to preload the bearings. On a threadless system you use a starnut and a top cap to preload the bearings before you tighten the stem.

This link from park explains it better than I ever could
http://www.parktool.com/repair/readhowto.asp?id=65

Star nut is part of a threadless headset system. If they say the star nut is fitted that means you don't have to do it yourself.

Example of a starnut: http://www.jensonusa.com/store/produ...-Star+Nut.aspx

Right i'm with you now, It seems obvious now i know. Thanks alot chaps.