Since this thread is specific to copper busses (I recommend nickel-plating), I just received a sample of copper sheets (I also added more listings as a reference).
wire diameter gauge and sheetmetal thickness gauge are two separate things!
listed below are what I could easily find available on the internet.
one-mil is 0.001-inch
0.40mm__16-mil__26 ga__12-oz per sq foot/B370 architectural 99% copper sheet
https://www.riogrande.com/Product/coppe ... oft/132126
5, 8, and 10-mil cuts with common scissors, 5-mil crumples easily, it feels like paper. I didn't even want any 5-mil, but it was cheaper to buy the sample pack that includes four types. At 0.40mm thick, its a toss-up between scissors and shears. Scissors could cut a sliver off of the edge, but it was hard, and I had little control in trying to cut a curve. If you need (or just want) 0.40mm, plan on ordering the busses to be laser-cut.
The four samples were from a DIY jewelry site, and look to be very pure copper by appearance. The architectural copper sheet was noticeably cheaper, but is only certified to be 99% pure copper. I suspect it will be conductive enough at 99% that this will not be an issue. However, it is made for the restoration of antique homes that used copper sheet in the roofing joints and rain-gutters. 16-mil / 0.40mm is the thinnest architectural copper sheet I could find. There are several thicker variants at http://www.onlinemetals.com
The common 18650-cell plastic holders have an 8mm wide slot for the common 7mm wide nickel bus-strips. If we limit ourselves to 7mm wide copper strips, then...the flat-bar to square-wire conversion is:
X 7mm wide = 0.91 mm squared, area in cross-section
X 7mm wide = 1.40
X 7mm wide = 1.75
X 7mm wide = 2.31
X 7mm wide = 2.80
Converting "flat bar" area of cross-section to round cross-section copper wire equals =
http://www.engineeringtoolbox.com/awg-w ... d_731.html
I have found conflicting info for wire-ga to amps on the internet, do not use these amp-ratings without doing your own research first.