Flap Hinge Fabrication

The best of the original flap hinges was used as a pattern to locate holes for the new hinge segments. The #10 bolt holes are 9/32" from the outside edge of the hinge and centered on the hinge 1-5/8" on centers. The 1/8" rivet holes are 3/16" from the outside edge of the hinge, one hole is centered and the outer holes are 3-3/8" on centers with the inner holes 3/8" inward. All of that could be measured and done carefully by hand for one hinge. For 6 hinges, per flap, it is quicker to use a Whitney punch and duplicate the holes. The peened end of the hinge was opened and the pin removed. A segment of the new hing material was used to make a master by clamping the old segment to the bottom of the master with the loops pulled snug and centered to locate the holes. The Whitney punch with a nibless punch was used to duplicate the holes in the master.

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The new blank was then placed under the master snugged, centered and clamped so the holes could be transferred from the master to the new segment. This require another modification to the poor old Whitney punch to add a clearance for the loops. This was easily done with a file and some careful cleaning before putting the punch and die back in.

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As each hole is punched a cleco is installed to help assure nothing moves to mess up the hole alignment. The same process was then used to make the other halves.

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The last thing to make was the hinge pins. These were cut from the pin stock with snips, the ends squared up on the belt sander and, a slight chamfer added to deburr the end.

With the pins installed the ends were peened with a hammer making sure both ends were closed enough to keep the pins retained like the factory hinge.