[sanddrag]

Originally Posted by Al Skierkiewicz

I always thought a broach was something you used to finish what was already roughed in. (i.e. an edm or wire operation needs to be finished with a broach to make it smooth and accurate.) Any professional machine ops out there to answer?

I am no professsional machinist but I have done keyway broaching. It is basically a "staircase" of cutting edges and with each "step" it takes off a little more material. For the keyway, you start with the round bore, but the broach does the entirety of the slot. They have hexagon broaches too. You start with the round hole and on the broach may be like a foot long and on each step the cutter gets a little larger and a little more hex shaped and by the time it gets all the way through you have a full hex. I really thought there were Double D broaches, but I could be wrong.