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- Jan 14, 2012
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Question for the group on making holes in spars. I'm getting ready to gear up and build the small flaps for one of my projects. Making an alignment tool to bore the holes for the hinge castings is not a problem. Where I'm needing information is tool selection for actually boring the holes. On this airplane, all the holes for the hinge castings have pressed in aluminum bushings through the wood. Bushings are also used throughout the airplane where there are significant loads and the need to prevent crushing the wood. The bushings appear to be pressed into the wood, with only mild pressure. There are no adhesives and the bushings are not knurled or otherwise manufactured to give them grip in wood, beyond friction.
My question is, what type of boring is going to give me the quality hole I need for these. Forstner bits, twist drill and ream, brad point bits, custom plunge router bits or ??? Spar thickness for now is 1.5" and under, but eventually I will need do do this on some 6" thick built up spars. Bushing od's run from about .250" all the way up to 1.5" or so.
My question is, what type of boring is going to give me the quality hole I need for these. Forstner bits, twist drill and ream, brad point bits, custom plunge router bits or ??? Spar thickness for now is 1.5" and under, but eventually I will need do do this on some 6" thick built up spars. Bushing od's run from about .250" all the way up to 1.5" or so.
