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That sounds like a solid idea. I will look at that. I have the bit so why not try it? Thanks.

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[quote="kxw2x2"]That sounds like a solid idea. I will look at that. I have the bit so why not try it? Thanks.

Resurrecting this old thread. I am curious to hear how a modified bit mentioned in the previous post by Phil (holding a flat grinding stone on the edge of the bit spinning in the drill press) worked for you. I am ready to upsize the forward wing bolts with the 1/4" pilot holes drilled through the forward/aft attach angles the Sonex way. My AN6-44's mic out at .372 and a pair of AN176-50's (still searching for -44's) mic out at .374. I have been hesitant to do the final drilling...

If you are trying to get to a very specific measurement, a reamer is your friend.
Drill undersize, then ream for precision.

Area 51% wrote:If you are trying to get to a very specific measurement, a reamer is your friend.
Drill undersize, then ream for precision.

+1. I reamed the Spar bolt holes to final size. I also purchased over sized shank NAS Bolts and frozen them to get them in.

Thanks for the suggestions.

Drilling by hand with a 1/2" cordless electric drill without ovaling the holes will be tough for me.

Another member kindly loaned me his (Fastenall) 3/8" double margin drill bit with a 1/4" pilot he has used. The test holes come out nice with the AN6 bolt sliding through without any resistance resulting in slight wiggling once seated on the block. The AN176 bolt fits the same with less wiggle when seated. I am sure the weight of the wings would make a nice fit through the spars, but wonder about the forward and aft attach angle wiggle that seems to be the stickler where others have redone their blocks and attach angles. Is there no movement at all allowed at the attach angles?

I am also looking at step drilling just short of 3/8" in 1/64" increments like others have done with some homemade drill blocks that will sit flat on the rear spar tunnel gusset to keep the bit straight as it passes through the spar and attach angles and final ream with an adjustable reamer, or maybe a piloted reamer once I find one.

tps8903 wrote:

Area 51% wrote:If you are trying to get to a very specific measurement, a reamer is your friend.
Drill undersize, then ream for precision.

+1. I reamed the Spar bolt holes to final size. I also purchased over sized shank NAS Bolts and frozen them to get them in.

Chris, what reamer and bits did you use? Do you happen to have the NAS bolt part number as well?