At times when Skyrim plays their loading screens it's states that crossbow bolts and arrows can be crafted at the blacksmiths but if try it out you only can craft arrows not bolts for the crossbow then Bethesda creates this character "Serana" who many fans of skyrim would like to marry her but can't. So Bethesda please update this.
Welcome to the forum...the wrong forum for your thread, but still. There is a forum for Dawnguard material. Click the report button below your avatar and ask a moderator to move the thread for you.
i have not tried this but i heard that you can only craft crossbow stuff like bolts at dawnguard forge in the fort dawnguard... lol it rhymes but yeah anyways thats what i've heard from other people in this forums are saying.. so try it at the forge in fort dawnguard