Just thought I'd do a bit of show and tell on how I cut .040" aluminum sheet, again. I do this also on the 7's.
No matter how careful or relaxed I am, I can not cut a straight line with shears, a least not to my critical eye.
So this is how I do it. I use a 1/8" x 1 1/4" x 8' long straight edge. I also use a 1" sq 4' and 8' long piece of tubing for clamping the sheet along the edge of the table.
Measure the sheet to be cut, clamp the straight edge to the marks. Use carbide scribe to score the sheet. I usually score the line about 14 times, 2 very light passes at first to set the line, then moderate pressure to score the line.
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Remove the straight edge and sweep the swarf from the score line.
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Then using square tube I clamp the sheet to match the score line to the edge of the table (it helps when the table has a sharp edge to it).
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Then using both hands, palm on sheet along score line and other hand bending sheet down. It usually takes about 3-4 passes, using greater force each time, to bend the sheet along the score line. Once resistance starts to lessen, I bend the sheet up and down a bit at a time till the score breaks.
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I then take a file and dress the edge. Prevents bleeding when working with the sheet in the future.
The following pics use the same process to score and break a 82" sheet. This method results in a very satisfactory edge to the critical eye.
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