This is for RV-6A builders who have yet to drill the steel weldment gear leg mounts in unison with the main wing spar (section 8 page 8-9 in the latest construction manual).
The instructions read "Now the real
fun begins. Holes must be drilled through the mounting plates of the gear leg mount, using the pre-drilled holes in the spar as drill guides. If a 3/16" drill were initially used, side loads encountered while drilling could easily cause the holes in the aluminum spar to become oversize. So, drill guide bushings should be used in the spar holes to permit accurate drilling of the holes in the steel mount....Four holes in each of the mounts are to be enlarged to 1/4". These can be drilled at this time. First, drill 3/16" from the rear, forward through the steel plates. Then, from the front side which is more accessible, enlarge the holes to 1/4" diameter".
The problems that I encountered with the latter part of the instructions for enlarging the holes to 1/4" is that: (1) The gear mount tube obstructs access from the front for one of the holes and (2) it is difficult to drill a perpendicular 1/4" hole free-hand through a 3/16" pilot hole. I managed fine with enlarging seven holes, but the 8th is slightly enlongated (see att pic). Vans support says "build on" but I'm not very happy with the result.
If I was to do this enlarging to 1/4" a better way, it would be to drill the holes in the spar using a drill press
. Ideally, this would be done before building the wings, but it could also be done before installing the wings in the fuselage. The fuselage bulkhead holes would still need to be enlarged after fitting the wings, but this would be relatively safe and easy as it is only .062 thick.
Please don't make the same mistake that I did.