A lot of people dont think of it this way, but it is true; the first machine tool was a file.
The old time gunsmiths didnt start out with octagon barrels, they had forge welded wrought iron or, if a fancy-dandy shop, rolled round stock often from England.
They would 'draw file' the flats.
You can too, using the proper technique and time.
Hit the I-net, or the library and check out how.
BTW, the nice thing about filing is that you dont make expensive mistakes so fast you didnt see it coming.
