Originally Posted by DiegoFrogs
As to the effectiveness and/or usefulness of a keyed washer in bicycle headset specific applications, I cannot give any opinions. It is helpful when discussing useless features with others to use similar terminology, and that's why I introduced the term, albeit late in the discussion. Keyed washers may just be a remnant of some other application in machining or some such thing (I would certainly expect keyed fittings in some timing cam applications, where orientation is essential), and many reflector brackets that interface with the headset have these keys to keep them oriented properly relative to the steerer. This type of reflector bracket functions essentially as a keyed spacer/washer. That's probably the historical basis for some threaded steerers having keyways. As long as there's a keyway in the steerer in order to accept a possible reflector bracket, one might as well manufacture a keyed washer for this application. They certainly aren't as ugly as the type of reflector brackets to which I referred.
It's cool; I wasn't referring to anything you said, just the keyed washers themselves. Keyed applications elsewhere do have merit, i.e. the Woodruff key system used to secure pulleys to shafts. Of course, these are usually a bit more robust than a bicycle HS, which is why they work.
This brings me to my second point: Nowadays we are so weight conscious that these parts are almost always Al, which is one reason why the key shears off so easily. This wasn't always the case; I remember the all-steel Campy headsets that were the industry standard for forever until the Al units started appearing on the market. Then there were the saw-toothed washers, with serrations that locked into the upper race. Still, all of these headsets required 2 wrenches to properly install, and if you tried to use only one wrench the key would jam into the steering tube threads.
The reflector bracket came later as the Consumer Saftey movement gained momentum; don't get me started on
them...