Originally Posted by
urbanknight
Any threaded fork would come precut, because only the top inch is threaded so if you have to cut 1" off, it's not threaded anymore. You're correct on the formula, though.
Have you done that on a threaded steerer? Considering the headset races go into the head tube and the to nut screws onto that but can't bottom out on the steerer, I don't see how that would work.
No, they don't always come precut. They come with an extra long threaded portion so the fork will fit a range of sizes. You have to cut the steerer to length, just like a threadless setup, but you have to be careful not to screw up the threads.
The spacer goes under the top nut. I've seen 20mm of spacers used. It's a way to get the bars higher without using an extra tall quill stem. You could probably find an example on the Rivendell site. Velo Orange sells a 10mm spacer that's drilled and tapped for a bell.