Today when we want to put a hole through a relatively thick piece of iron, most folks will turn to their electric drill or drill press. Though augers and braces and bits have existed for centuries (for instance the early 15th century image of St. Joseph from the Merode Altarpiece), these type tools are best suited toward wood and not iron. The drill press eventually came along, but about two hundred years or so ago. So what’s the solution? why fire of course. When a smith needs to make a hole in a piece of iron, he will heat the piece to a white hot and by use of a “hot punch” strike a divot in one side of the iron, then flip the metal and strike again with the punch on the reverse. The technique produces a small flatten slug and of course the hole. One of the telling signs that this has been done is that there is also a slight swelling of the iron to either side of the hole. Rather than having a large series of punches to make different size holes, smiths will often drift the hole to enlarge it.
In this video by Joe, a blacksmith in the Netherlands (www.youtube.com/user/TechnicusJoe) demonstrates how to convert a cross pein hammer to a functional hot punch and how to use it to make the hole and then drift it.