Its really really really hard to tread a threadless fork, but it is really easy to replace a threadless 1" fork with a threaded one. You will have to swap your fork, headset, and stem. If you already have a stem that you really really like, or want to use "oversided" bars there is a product that you can get that allows you to use a threadless stem with a threaded headset. You can get it in 1" or 1 1/8"