I'm building up a commuter bike for my daughter, and need a fork for her bike. Her brothers who all ride a lot are much taller so their old threaded forks are too long. Can I cut off a threaded threaded fork steerer tube knock in a star fankled nut and use a threadless headset. Thanks for the help.
If you're sure it's still going to be long enough for any needed spacers and the threadless stem clamp, go for it. If the headtube length on the boy's bikes is less than 2" longer than your daughter's HT, you'll probably come up short. That's without cutting the threads off, but you don't have to cut 'em off if you need the length.