Brief Description: Countersink Bottom of Spar for Skins
I finished countersinking all of the holes for the skins on the bottom flange of the spar today. My technique is pretty standard at this point - Clamp a supporting piece of aluminum on the inside face of the flange and countersink away. This provides sufficient material to fully support the pilot bit. This would have gone faster if the holes were evenly spaced all along the spar. That way I could have done multiple holes before advancing the little support strip of aluminum. However, each time I advanced the strip, the predrilled holes that I had in it no longer matched up with the holes in the spar. Oh well. Countersink one hole, advance, countersink another hole, etc. Once all of the holes for the skins were countersunk on the bottom flange I used a deburring bit in my right angle drill attachment and deburred all of the holes along the inside face of the bottom flange. I usually turn the pressure down to the lowest setting that will actually activate the drill and use this for deburring. Works great!
Countersinking bottom spar flange for skins
Deburring bottom spar flange
All holes countersunk and debured on bottom flange of spar
