Brief Description: Fly Cut Holes in Inboard Tank Ribs
Used the T-407 reinforcing ring to find the center of the hole to cut in the rib. Centered the ring on the raised flange of the rib and connected opposite screw holes and rivet holes with a straight edge to get a good intersection at the center point marked with a sharpie. Clamped a piece of MDF to the bench and clamped the rib to the MDF and bench. Center punched the mark and pilot drilled with a #30. Set up the fly cutter to the proper radius and used an electric drill to slowly drill in the centering 1/4 inch bit. Double checked the flycutter tracked perfectly around the outside of the raised flange of the rib, then slowly ran the flycutter into the rib. This technique was demonstrated in an EAA Hints for Homebuilders video using a completed fuel tank, but worked very well here. A few tense moments when the fly cutter dug in and broke loose, but overall a smooth and controlled operation. Ended up with a perfect hole. Repeated the process for the other tank's rib.
