Work continued for a little while this morning on the stabilator’s rear spar. The holes for the AN3 bolts that will attach the upper and lower control horns need to have nutplates installed for the bolts to thread into. A bolt is threaded into a nutplate to keep it centered with the #12 holes that were previously drilled. Once the nutplate is centered on the bolt hole, the two rivet holes that attach the nutplate to the rear spar can be drilled. One down ... three to go.
Match drilling one of the four control horn mounting nutplates
to the rear spar.
Looking closely at the above photo you may
notice a new tool. The DOG Aviation procurement department purchased a few of
the stubby Clecos in both #40 & #30 sizes. When drilling holes that are close
together, the taller standard Cleco is tall enough that the chuck of the drill can
easily hit the Cleco when the drill bit pops through the hole being drilled. No
worries when using the stubby Cleco on close holes. The stubby Clecos should also make setting some rivets with the
pneumatic squeezer easier as well … Quite often the standard Clecos get in the
way of the body of the squeezer.
After the nutplate holes in the rear spar were drilled and deburred, the nutplate rivet holes on the outside surface of the rear spar need to be countersunk for flush rivets. A piece of wood with a # 40 hole drilled in it is clamped to the underside of the spar. This prevents the tip of the countersink bit from enlarging the hole because it prevents the tip from wandering.
Using the #40 100 degree countersink bit in the countersink cage. The countersink cage was set to the proper depth for AN426AD3 rivets earlier in the project so it took only a few moments to complete the countersinking.
After the nutplate holes in the rear spar were drilled and deburred, the nutplate rivet holes on the outside surface of the rear spar need to be countersunk for flush rivets. A piece of wood with a # 40 hole drilled in it is clamped to the underside of the spar. This prevents the tip of the countersink bit from enlarging the hole because it prevents the counterdink bit from wandering.
Up until this point most all of the countersinking has been done on the drill press. However, the spars are just excessively long to try to balance on the tiny drill press so the air drill was used. I discovered a few weeks ago when playing around with some scrap metal the air drill spins WAY to fast and the countersink bit tended to chatter causing an uneven countersink. Placing a multi-turn air valve on the air line to the drill solved the problem. The air was adjusted so the drill turned really slow with almost no power .. this actually resulted in wonderful countersinks in a few moments. The multi-turn air valve/swivel can be seen in the first photo of this post. I can highly recommend getting a multi-turn one as opposed to the 90 degree ball valve type because a really fine adjustment is possible which is useful for the air drill and die grinder outfitted with a Scotch-brite wheel.