Headset (bicycle part) - Wikipedia, the free encyclopedia
This picture shows the spacers that can be use without cutting the steer tube
Servicing Bicycle Headsets
Star Fangled ® Nut
A special nut that is designed to be hammered into the steerer of a bicycle with a thread less headset, such as a Dia Compe "Aheadset" ®. The adjusting bolt screws into the "Star Fangled Nut."
The star-fangled nut has two barbed steel flanges that allow it to be forced downward into the steerer, but which prevent it from moving upward.
If you ever need to remove a star nut, the easiest way is by driving it down and out the bottom of the steerer with a hammer and punch.
Star nuts are only for use on metal steerers and should never be used on carbon steerers. Forks with carbon steerers generally come with special expansion plugs that serve the function of a star nut, without the sharp edges that might damage the fragile carbon steerer.
Star nuts are available in several diameters to fit different types of forks.