Drill bits to drill main spar attach holes.

[Sonex1243]

So for those of you who have drilled out the attach blocks with 3/8 bit and used AN6 bolt or trailer hitch pin – have you been happy with the fit? I’ve heard comments about having to lightly “tap” the bolt or pin into place after drilling.

I used the Fastenal bit I linked to earlier in this thread (sounds like the same one you are using). Unfortunately, I don't remember the diameter I measured for the AN6 bolt. My experience was the same as Corby202--only had to tap the bolts in when installing on the airplane.

I occasionally shake the airplane by the wingtip to see if there's any looseness and I haven't noticed any.

Chris,

Do you still have the Fastenal bit and would you be willing to loan it out? At the rigging stage now and getting everything set up for drilling. Thanks.

[Zack]

I used standard drill bits and reamers create the 3/8" holes in the spars before mounting them to the fuselage and ovaled the holes this way. This is how I corrected the ovaled holes. On the B model the final size is 0.5000, and I determined I needed a little more that that to clean up the holes, so I selected 0.5625 as the new target. I updrilled the fuselage attach points to 0.5000". Then I created guides made on a lathe from 0.5000" steel tubing to updrill the spar first 3/8", then 7/16". This got me a true hole of 7/16". I then used piloting reamers through the entire stack until I reached the 0.5625" final size. The tooling expense was high, but I saved the spars. The hardest part was sourcing an upsized bolt, this is what I used:

https://military-fasteners.com/bolts/sh ... nas6209-64

If I were to do it again, I'd use double margin drill bits to a smaller than final size, then work to final size with piloting reamers. I always drill undersize and finish ream, but a standard reamer can cut sideways if you don't have a solid jig/fixture. I purchased my piloting reamers from Pan American Tool.