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Drilling Aileron Counterweight

asw20c

Well Known Member
Today I was at the step where the aileron counterweight must be match drilled with the supporting nose ribs, and nose skin. I found it to be very difficult and ended up smoking 4 brand new, aviation quality drill bits before pulling everything apart and drilling on my mill instead. You could easily see the transition from cutting, then within maybe 2-3 seconds, dulling and melting so I'm guessing the 304 stainless gets hard quick when it gets hot. My drill bits literally had a round blob of metal at the tip where they melted. How did the rest of you deal with this step? I spent about 6 hours today just drilling the counterweight on one aileron. Any tips for a more effective way to drill this material? I also tried boelube and cutting oil.
 
I just did this yesterday. Took all of 10 seconds per #40 hole. Drilled pretty normal I thought. I just used a 6? aviation quality drill. Can?t imagine why you are having trouble. I didnt use any lube, either. The trouble I am having is stretching that nose skin back to the spar. Man that is tight!
Jerry
 
Huh. I don't get it. My drill bits are quality cobalt steel. What RPM are you using? Maybe I'm turning too fast?
 
Well I knew it was stainless steel, so I used my electric cordless, which turns about 800, I think.....at least not 4000 like my air drill. Maybe that was it?
Jerry
 
I did these this past week on one of my ailerons. I did the first one with a small cordless drill, feathering the trigger way to slowly with probably too much pressure. The bit wandered, even after using a centerpunch. I marked the rest of them and punched a center hole to mark the tube. Put it in a vblock and used my floor drill press with lots of liquid boelube. Each hole was probably 4 or 5 seconds, no problem at all. I just checked which pulley setup I was using and it turns out that I was at 2620 rpm, which is too fast for this size drill bit. Worked fine, though with no problems.
 
Just drilled my right aileron this morn. Because of the odd angle on the nose ribs I just started the holes slightly then disassembled it and then final drilled. I was using a quality cobalt bit and drilled only about half speed. Only took about 10 seconds.
 
Best approach to avoid the hardened material and Chernobyling your drill bit is to understand you add pressure sufficient to constantly undercut the surface of the hardened material made by the previous pass of the drill point.
 
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