holes

[yesteryearforge]

do you punch your holes or drill your holes or do you drill a hole and then drift it to size to give the appearance of a punched hole ?

[Glenn]

Sort of depends on what I am working on. The one time I drill is when I am tapping threads. If presision is needed, I think drilling, if blacksmithing is needed I think hot punching. Besides the piece is most likely hot anyway.

Several holes in a length of flatbar can be done either way but forging will stretch the bar will drilling will retain the dimention. This is where we need to hear from the traditionalist on how to hot punch and keep the holes on dimention as the bar stretches. Any takers on that question ?

[Ed Thomas]

Sometimes it is appropriate to drill holes. However, try to think of punched holes as the forged iron flowing around the hole and reconnecting, rather than making a hole. The amount of iron you remove in punching a hole is negligible. Instead, you are forging almost all the iron around an opening. That is what makes forged holes so beautiful; the flowing from one side to the other.

There is always a lot of "discussion" about the technique for this. I go with the quickest way, which does require a bit more attention and skill. I use a slot punch (not a slitter). Drive till its dark outline is seen on the opposite side. Then shear the plug. Upset the new slotted hole until it is round, and drift to clean it up.

Recognize that this will make the bar slightly shorter for each hole. So the easiest way to get accuracy is to use test pieces. Mark and measure, then punch, upset and drift, then measure the difference.

As in all forging, iron will bend toward the path of least resistance. If you punch slightly off-center, the thinner side will open more easily and drift more easily, thereby skewing your hole toward one side. Likewise, if you heat one side of the slot more than the other, it will be softer and bend more easily thereby stretching the material on the hotter side and skewing the hole.

You can take advantage of this knowledge. If your slot is slighly off-center, you can keep it toward the center by heating the fatter side more than the thinner side.

Don't fake things. Either do them or don't do them. Drill or forge. It's much easier to forge it than to fake it anyway. And if the forging doesn't matter and you need accuracy, then drill the hole.

There are other ways to punch holes which depend on material. If you give an example of what you wish to perforate, we can give you specific opinions. For instance, sheet metal is a different issue.

[irnsrgn]

I usually punch holes, I mark with center punch when cold, then heat up and use a chamfer punch in the center punch mark so when I position the punch it will line up exactly in the center. When I punch, I never hit the punch more than 3 times before cooling in a small can of water in front of my anvil. If the punch gets hot and the end swells some in the hole you have a hard time getting it out. I keep punching from one side till the punch bounces and the metal under the punch is compressed as much as it is going to. Cool the punch again, turn the piece over and picking the punch out of the cooling can leaving a drop of water on the bottom position it over the black spot on the iron, the drop of water cools the thin piece and thus it will shear out instead of stretching back down in the hole. I then drift to size and if it is going to be tapped I drill a little out to the proper size. I also slot punch the ends and use a bolster underneath the width of the slot and then spread with a slitting punch and then drift to size. then work the square corners down over the end of the anvil horn careful not to enlarge the hole and then drift again at a dull red heat.