If you have large power tools, like a large bandsaw or table saw, you can cut up 3/8" squares from logs and turn them into shafts with a hand plane- or, if they're still slightly green, chuck them up into a corded power drill and run them through a piece of metal with graduated holes cut into it. The second method takes about ten minutes a shaft, maybe five if the grain is straight. I prefer this method as you can just use small billets from a stave tree, and hickory makes such sturdy arrows I wonder if modern carbon arrows could have met their match (hickory flexes, they don't).