I want to build a portable grill out of this canister, what's the best technique to make a perfect straight horizontal cut a couple inches above the solder?
If I were doing that project myself, I would take a ruler and sharpie, and mark the desired distance from the weld at several spots around the tank. Then, using a ribbonlike strip of material (I'd use a thin strip of metal, but heavy paper, card stock, or plastic would work so long as it's wide enough to avoid flexing the wrong way), loop it around the tank on the marks and trace the line. Then cut with an angle grinder (cutting wheel). Make a careful, slow, shallow score along the line first before cutting through to help prevent wobbles. Then use an angle grinder (flat disk sander) to flatten out any uneven spots and deburr the edge.
The combination square technique would work, but this will give a nicer line. With a cutting wheel, a nice line can make a big difference to the quality of the cut.
This is precisely how I cut the tops off water heater tanks for conversion into furnaces and 44 gallon drums for planters/fire tubs. Get into it OP.
> using a ribbonlike strip of material.
I keep a few lengths of packing tape around for this. Also great for marking lines around PVC pipes and pine logs (or anything round of a decent diameter for that matter)
It's just too simple for some.
I jigsaw with a metal blade can cut this just as easy those tanks arent that thick. just draw an even line around the tank, plunge cut the first hole then follow it with the jigsaw carefully. grind and sand edges smooth. done deal