Hey, no kidding, I sat in that B47, too. Pretty!
My guess is that it is a tool reference, not a dimension.
Bell would naturally have standard tools made for flanging holes, (like everyone else) so instead of specifying all dimensions and angles for the lightening hole, the draftsman could just call out the one tool required to make the hole. Done.
We've made a few such tools in our shop, from time to time. One tube + one plug, made with a lathe, fitting together, ready to be squeezed in a hydraulic press, made so as to locate center, shear through, flange the edge, and slide out, all in one operation.
Maybe, somewhere in a factory in Fort Worth there is a shelf with a row of round plugs and sockets that fit together in pairs, and one of them has "50HI-14" stamped on the side.
As for what to do about the part, either locate the tool (lots of aimless phoning around IMHO) or just scale off the drawing what you need and then make your own tool. Bell parts can be flanged 45 degrees in some places, or 60 or 30 in others, depends on where you look. Compare with other parts you may find a similar hole (theoretically made with the same tool) to this one and measure that directly to find out what the end goal really should be.
STF
