I'm needing to build a bulkhead panel. I'm using 1/8" 5086 Alum. I tried drilling holes (using used, cheap drill bits) and all my holes blow out on the back side, causing massive amounts of burs, and when I use a de-buring tool it ends up egging out the hole and leaving a highly chamfered hole behind. Is there a secret to drilling holes and having a beautiful hole behind with little to no burs? We have a mill here with a $400 set of drill bits, which I'm going to try next, but I was wondering if I could have had the wrong spindle speed, possibly wrong lubricant, or too fast of feed rate (I did go slow at times and quality of the hole didnt change). I'm needing to drill holes from .800 to .125 dia. Anyone have suggestions?


David

Drill the hole into scrap material on the other side. Let the scrap material blow out.

The secret here is to have signifigant clamping force between the good material and the scrap that you're drilling into. Often the force of the drill is enough, but a bit more doesn't hurt.

Basically, take some leftover 1/8" material and put it under your good material. Drill through the good material into the scrap. The scrap will have a nasty "exit hole" but the good material will look good. This works great for wood, too.

It's possible you can use some good, smooth hardwood as a backer but you'll probably get best results by using the same alloy as a backer. You certainly don't want to use balsa wood or stainless steel as a backer.

Heh. I figured that in order to learn this, he's gotta have some scrap 1/8" material around.

It seems wrong, but for me, higher speed helped. I went too slow the aluminum got hot, became more maliable, and made the huge blow outs if. When I went a little faster, the bit just ground the aluminum away like wood and there was no problem.