Myron, Seriously, I usually use a scrap piece of thin ali sheet (litho plate or foil meat tray) to act as the spacer and heat protector. What you really need is a high wattage soldering iron (I use an ancient Solon 125 watt) to get lots of heat to the joint quickly. This heat the piano wire quickly, where you need it, and makes the joint without having the iron in proximity to the wheel for any longer than neccessary. This I think also amswers (in part) the original question. A very hot iron that heats the wire locally, and briefly, will make a good soldered joint without affecting the metalurgy all that much. Blowtorches are a different matter maybe. David