Here we go on the F-704 fuselage Bulkhead. Looks like we'll assemble many bulkheads and then add stringers and skins.
So, easy job you may say. just drill 12 5/8" holes to support SB625-7 Snap Bushings. These holes are for wire runs, manual trim cable and rudder cable. Things of that sort.
These bulk heads are made up of 2 short wing spars. The wing spar will bolt inbetween these shorter guys that live in the fuselage.
Anyway. here's the deal. I can't drill these holes where the plans call for them. Some of the holes are located wilth a pre drilled pilot hole. Some are not. The ones that are not are measured 1 17/32" from a reference position. I mark the position with an cross, put a punch mark at the location and drill a #40 pilot. The hole is a 1/2 drill bit diameter off from the desired location. What the heck? I then step drill the hole to 1/2" and check hole location and the 1/2" hole is off in a different direction. Dang it all.
The only way I can get the 5/8" hole at the location as per plans is to - 1.) Auto punch the location. 2.) Use a compass and draw a 5/8" hole around the punch mark. 3.) Drill a #40 pilot. Of course the pilot is off location. I don't care. 4.) Drill to 1/2" using my small step, step drill bit. It's way off, I don't care. 5.) Use a sanding drum to move/shape/enlarge the hole to 1/16" smaller then the final size. 6.) Drill to final size using a step drill that only has to step once or twice.
What does every one else do? My procedure seems like bull crap.
Now. I do believe that having these holes off from where the plans calls for them is not a huge problem. But, I still would like to locate them as per plans.
