Here's how I make my own smooth broaches; Start off with a piece of hardened pivot wire in the size range of the hole you're broaching. Chuck it in a drill and hold it against the side of a spinning grinding wheel at a very slight angle,less than 1deg(1 deg=.0175 per inch taper). Using progressively finer sand paper run the drill and smooth the grinding marks while maintaining a crosshatch pattern on the broach,if a little cutting action is desired stop at the coarser grit paper. This is what your finished broach should look like. The camera didn't pick up the crosshatching very well but it's there.