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Old 09-06-2018, 11:43 AM
cliffrod cliffrod is offline
MetalShaper of the Month January 2020, March 2022
 
Join Date: Dec 2014
Location: Spartanburg, SC
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Between the Redneck Roundup and Labor Day weekend, I bought a set of the first 5 books by Timothy Barton from AMS member Steve Colby in Alaska. In Book #5, hammerforms are discussed.

In order to keep a piece of metal tight against a form when it needs to end with a flange, it is recommended to turn the outer edge of metal in the opposite direction. In simple terms, it will look like a gutter or channel. Then a corking tool can be used (I used a hardwood tool) to form the metal tightly against the hammerform. I believe this allows the metal to be stretched to the form instead of being shrunken to it, which is what I thought needed to happen but didn't know how to accomplish.

Needless to say, it worked great. When I started the next blank for the top, it was finished almost as quickly as it started and turned out pretty good. As a result, there's not as many pics as before.







It went so fast that I thought I might have time to do the bottom half. Sitting there not wanting to cut new metal and looking at the failed top half from earlier, I realized that if I flipped the failed top half over, it would already be bent in that upturned channel around the perimeter. It was already scrap, so I gave it a shot. I'm glad I did. Here's the failed top half-



This is the same part, after about an hour of work-





For a completely flogged piece of metal, it turned out pretty well. I literally flipped it inside out and only had two small cracks on the edge. Very fast to accomplish, too. The surface would probably be smoother if I had any idea this experiment was going to work out so well. I really didn't think it was going to be any kind of success.



I hit these with the gas torch and a scrap of trimmed metal for filler and that seemed to work well.



Now that the top and bottom were getting close, I spent some time trying to smooth things. A couple of dollies (including one nice comma dolly I got from Dan Shady at the RR because I thought it looked exactly right for this project) and a polished flipper/slapper I made from an old file and surfaces are much better.



These will be painted, not polished. No abrasives yet and they're not perfect, but are getting better.

While I still had a long but uneven edge on the top half, I needed to turn a flange on the top part (per original) of consistent width. I made a tipper with a stand-off length on one side equal to the desired flange width. Another experiment, so I used a piece of scrap hardwood. It worked good enough that I would make others in more durable metal.





After the top flange was turned, the bottom was trimmed and trial fitting proceeded until things were acceptable.

I had an ongoing concern about how flat the pieces were & weren't, especially the top. they were close and I thought/hoped things might relax once I cut out the hole in the top half. Patience was the right approach. When I cut out the top and turned the flange, it settled down a lot.





Assembled, most of the fit is pretty good at present. The only problem is the filter protrudes above the top near the front of the assembly, up to 1/4" max. The bottom ring where the filter sits is not adequately level, so I'm going to stretch it a little deeper before I finish joining the top & bottom halves.






Some of the originals had spot welds to supplement the crimped flange. I'll add those after the fit is resolved and more is planished smooth. There will be more posted as it wraps up, but this is it for today.
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