My dad asked me to build something for him that was going to require a series to rollers. I could have built custom roller for this application, but it was most cost effective to buy off the shelf conveyor rollers. The downside of these conveyor rollers is that they have a hexagonal shaft. While I could have probably gotten away with drilling an over-sized round hole and just let the hex-shaft be loosely constrained that didn’t sit right with me. I also could have gone a very labor intensive route and drilled round holes and then filed them to shape, but I didn’t particularly want to do that either. What options were I left with? The proper way to cut a non-circular hole in material is to use a broach; hexagonal and square broaches are quite common. I could buy a hexagonal broach for a few hundred dollars, but this seemed silly for a tool I would only use for one project. So, instead, I decided to make one.