I marked the 1" hole center point and started with a #40 pilot hole to start. Then I opened up the hole to 1/4" Then I used a #5 unibit to open the holes up to 1" diameter. I double checked my dimensions and then cut the pieces. I was slightly larger than 2" so I ran them through the sanding station till I was satisfied.
Then I got to work drilling them for the spar. I marked out lines on the spacers to ensure that they would be centered with respect to the holes on the spar web. I taped the spacers onto the web and used a hand drill with a 3/16" bit to start the holes. Once the holes where deep enough, I took the spacers over to the drill press and completed the 3/16"' holes. Very nice. Too tight for an AN3 bolt though. I then set up the Tie-down bracket according to the plans.
I drilled the first hole on the tie-down bracket with the drill press but I just could not fit an AN3 bolt in. So I upsized to a #12 bit. This time the AN3 bolt would fit through the tie down bracket allowing me to bolt it to the spar. I taped the spacers back down again and began match drilling the holes.
The left side turned out great, so I moved on the the right side. After the right side was drilled. I noticed that one of my holes was slightly oblong. My stomach jumped to my throat. Shoot.
This must have happened when I taped the spacer back down to the spar. The tape had held the spacer just slightly off and good enough to let the drill bit dig into the spar. At its widest point its 0.207" across. Enough to raise my eyebrows.
Another look
The holes in the Tie-down and spacer are good. With good bolt fit through them.
I'm hoping that I will be ok as-is, and that I haven't done anything serious. Truly a silly mistake. The thought of going up a bolt size crossed my mind, and I double checked if a K1000-4 platenut will fit on the spacer but it won't. I might have to buy a special compact or one lug platenut if I have to go to and AN4 bolt.
Update. Van's recommends up-sizing to an AN4 bolt here.
Note to self for future....Drill these holes with the drill press!
