As @
Bill Kapaun notes, spoke threads are rolled, not cut. Some bike shops have spoke threading equipment. Phil Wood's is nice, as it rolls the threads and cuts to length in a single operation. But it's expensive (couple thousand dollars, last time I checked). Cyclo and Hozan have more affordable ones (couple hundred dollars), but in my experience, they don't do as nice a job, and you need to cut the spokes to the desired length separately.