The seat edging was next. This was made from aluminum sheetmetal wrapped around a 5/16-inch-diameter 6061 T6 aluminum round bar. I started by using a die on the Lazze machine designed to make the beltline on a '33 Ford. I cut several strips of aluminum 3-feet long and ran them through this die set, leaving a 1-inch-wide flange on one side. I wanted to turn this profile into a “question mark” shape and presumed I would do this by hammering, but I found that I could form the metal faster and more smoothly by squeezing it in a 6-inch flat-jawed vise. Once I had the curved part worked down to about 1/2-inch-diameter curl, I inserted a 3-foot length of the round aluminum bar, and used the vise to squeeze the sheetmetal down against it. To get the final tightness of the sheetmetal against the solid bar, I used the beading machine with the female half of a beading die on the top, and a urethane die on the bottom. I ran each piece through the machine twice; once right-side up, and one upside down. This finished off the three blanks for the edging very nicely.
Now the edging had to be contoured to match the seat, and I annealed the strips to ease this process. It's always best to do the most difficult operation first, and in this case that was the tight-radius bends on the two front corners of the seat. I bent these corners around a piece of heavy-wall tubing.
I used a shrinker and stretcher for the more gradual curves on the edging. Using these tools, it's easy to make the metal bend in one plane, but the center portion of the edging needs to have a spiral bend, and this was challenging. I accomplished this by doing the work with the shrinker first, then clamping the edging to a large-diameter piece of tubing, and hand bending it in the other plane. This took a bit of back-and-forth tweaking, but I finally got the shape dialed-in pretty well.
With the edging properly shaped, I clamped each piece into place and laid out the rivet holes. I decided to use 5/32-inch rivets, since I like the head diameter of these, but I used 1/8-inch holes for the initial layout so any slight misalignment could be dealt with later. I used a Whitney hand punch for all the holes (although they could be drilled), and then held each segment into place with Clecos, and marked the ends of each segment for trimming. The ends were cut, the parts were re-assembled on the seat, and the joints were tack-welded. After checking the fit one last time, the joints in the edging were finish-welded and sanded smooth. I put a lot of time into finishing this edging strip, removing all the marks that the shrinker and stretcher made, and smoothing the welded joints to perfection. Any cleaning up on this part has to be done before it's riveted into place.
The edging was positioned back on the seat, and I put 1/8-inch Clecos in every fourth hole. Next, I drilled through each hole location with a 5/32-inch drill bit. This match-drilling ensures perfect alignment for the rivet holes. With the drilling completed, the edging was removed, and both the edging and seat were very carefully deburred. This is a crucial step as even a tiny burr around a rivet hole will prevent the metal pieces from joining tightly when the rivet is set.
Next, I re-assembled the edging on the seat using a 5/32-inch Cleco in every hole, and I was ready to start the riveting. Rivets are often set with a pneumatic riveting gun, but I wanted to try using a rivet squeezer, so I ordered one online, and I am very impressed with the speed and quality of the riveted joints it produces! There are about 86 rivets in this seat, and every one needs to be properly done, so the rivet squeezer was joy to use.
The riveted edging was truly the finishing touch for this seat. It adds a lot of strength, gives the edge of the seat a smooth, easy-to-handle surface, and it adds a lot of visual appeal to the design. A seat like this would be a good project for an intermediate or advanced metalworker, and you are welcome to contact Ron Covell if you would like a set of patterns of this seat, or a DVD that shows its construction.
21. The seat edging required several bends, and I made a simple fixture to make the tightest and most difficult bend first. Notice how I'm using the vise to hold the edging against the fixture.
22. The edging was made in three sections, and much of the forming was done with a shrinking and stretching machine. Here I'm checking the fit against the seat.
23. After each piece of the edging was properly fitted, they were welded together and smoothed. In this shot you can see the 1/8-inch pilot holes for the rivets.
24. The edging is clamped to the seat, and each rivet hole is match-drilled, then the parts are disassembled and deburred. Here the parts are reassembled and held with Clecos.
25. I'm using a rivet squeezer to set the 5/32-inch universal-head aluminum rivets. There are about 86 rivets on the seat, and the rivet squeezer really speeded the job.
26. You can see how the edging not only strengthens the seat, but the uniform rivet spacing gives it a design element, too.
27. Here's a bottom view of the finished seat. Since this seat won't be painted, I took extreme care to
prevent the metal from getting marred from handling.
28. And here's the front view. I must say, I am extremely pleased with the finished product, and I would encourage any of our experienced readers to try their hand at making their own bomber seat.