But the problem with the metal gearsets is that they tend to be made out of soft metal -- brass or aluminum. I suppose someone somewhere makes them out of steel, but those aren't normal hobby store finds.
So, one must limit the use of the metal gearset idea to softer materials, such as expanded PVC, maybe nylon, or polycarb or acrylic if the metal has been heated up. For plastic it definitely helps to drill that pilot hole for heated stamping so that there's no flash left over to carefully clean up. The trick is not removing the spline too soon, or else the plastic contracts too much when it cools.
-- Gordon