Aileron Counter-Balance Hole

[Weldingiron]

Good Evening Bearhawkers!

I got the first hole drilled for the counter balance tube and I'm almost happy with it. I'm using a step up bit and it contacted the flanges and cut into the metal and scratched them up a bit. In the picture, the protective plastic makes the edges look ragged but I think you can tell the part I'm talking about. I'm guessing I can just smooth it out with sand paper, deburr the edges and be good to go, but I wanted to run that by the forum first. Thanks in advance!

[Chewie]

I used a rotobroach and a fixture on the drill press with mostly good results. I had to practice a couple times to locate the rib so that I would not damage the flange or punch through that narrow ligament on the leading edge.

[S Lathrop]

I try to use punches on sheet metal when ever possible. Here is what I used www.mcmaster.com/knockout-punches. The rotor broach would be my second choice but it is a good option.

I have also reground drill bits into sheet metal drills. I have never seen these for sale but they are ground like a wood bit with a center guide/drill point and the outer edges of the bit are ground to do the cutting. It takes some time to get the shape just right but they work very well. The shape is much less aggressive than a wood drill but the same idea. But with the arrival of the step drills, I have not used the sheet metal drills.

[Weldingiron]

For the knockout punches, did you use a jig to make the pilot hole uniform on each rib? I have access to a set of these so may try and go that route.

[S Lathrop]

I iocated the hole for the balance tube when I made the rib blank. But a simple guide can be made to locate the hole once the rib is formed. That might be better than what I did because you would locate all the holes based on the actual rib.

[svyolo]

I never used a step drill before this project. At first I loved them, but someone mentioned the hole could move as it got bigger. I now stop a couple of steps before the final, and adjust the hole to get it where I want it to be. I don't love it anymore, but still like it. It makes beautiful holes, but I would not call it a precision instrument.

[S Lathrop]

Earlier we were talking about Greenlee punches, step drill and Roto Broaches.

Today I needed a 1.125 hole in sheet metal parts. I wound up using a APT Multi Tool Interchangeable Blade System. The set I have goes from 15/15 to 1 1/2 in 1/16 increments. The blade holder has a 1/2 inch shank. This set is a nice addition to a Rotor Broach which stops a 3/4 inch. The Multi Tool requires a 3/4 guide hole. This tool needs to be used in a drill press. I have used this tool on the lathe to bore aluminum parts.

Just something else to consider for making precision round holes in a verity of sheet metals.

[Weldingiron]

After serious paralysis by analysis, and a few methods that ended up using up my reserve of spare ribs I'd made, I was able to get good results using a forstner bit with a jig on the drill press. Thanks to everyone for the input!