Yea, as Schrub said, you can just get the regular (no flux core) solder, and use flux seperately; just make sure to use acid flux (rather than rosin flux), as that will be the most applicable for what you want to use it for. You can also get the acid core solder (as far as I know at least) if you want, but using flux seperately would be a good idea anyways, even if you use this kind of solder. Yea, and.. again as Schrub said, if you're going to use a soldering iron, you'll need a fairly large tip, because you're going to be heating up a big peice of metal (your tension wrench).
Well.. hope that was somewhat helpful, lol.