I've tried it i also saw indeed you can only use specified items tried it with wood and bone neither will work nothing pours from the smeltery.There's only a few things you can make it out of these days. Use the in-game manual to make sure you're making the shaft out of the correct material. I think it's limited to: Wood, Bone, Blaze Rod, Endstone. Or something like that. Maybe there's one or two others, but that's mostly it. Any other rod won't work.
actually I was able to make a metal arrow shaft.....but it wasn't very goodArrow shafts are much more limited in materials. Wood, Sugar Cane, Bone, Blaze and ender rods are the only options iirc. You can't make one out of say stone or a metal. In 1.10 tinkers it's arrow shafts you use over tool rods.