Drilling holes in MS with a cordless drill

[Techie1961]

There has been a lot of discussion on the forum recently on drilling so I thought that I would share a technique that I was taught when I started my apprenticeship many years ago. In the manufacturing plant that I worked in, there were some Swiss and German master Tool and Die Makers and one of them shared this technique. In a manufacturing plant, it is really important to get things done quickly so that you minimize downtime. As a result, we often ended up inside of tooling trying to make repairs. We learned to do things quickly and effectively.

In the video at

I drill a 17/32" hole (clearance hole for 1/2" bolts) though a piece of 3/8" MS plate. If you already know all of this, great. It is just here for those that don't.

 

[bggrnchvy]

There's a subtle science to making holes with twist drills a lot don't seem to grasp that is even simpler than twist rates, feeds and speeds and point angle.

There's a dead spot on every twist drill that doesn't cut very well. It's the width of the point turned into a diameter about the true center.

If you take a small drill with a tiny dead spot and drive it through first removing the material the larger drill bits dead spot would have been pushing against you'll be taking the drive pressure required down a lot.

Depending how big the end hole needs to be you may have to do this once or many times.

 

[Techie1961]

There's a dead spot on every twist drill that doesn't cut very well. It's the width of the point turned into a diameter about the true center.

It's referred to as the chisel. With cheaper drills, the chisel (which is more or less relative to web thickness) gets thicker and the force required to push the drill gets higher. It's a balance of drill material strength and minimum thickness of the web that makes a quality drill (among a lot of other things). With some skill, you can counter the effect of a thick web with some sharpening but it can only go so far. The flute has to clear the chips.