To cast a circle a sword or dagger may be a suitable substitute for a wand as they both can direct the energy necessary to cast a circle. A circle casting is very protective casting and a sword is a representation of how one would be blessed with protection so the use of a sword for casting a circle is possible.I however would not consider a sword a proper substitute for a wand in a different type of casting. When stirring or mixing a spoon or paddle is a better wand than a tool originally intended for cutting or dividing. So a sword or poker would not be a good substitute for a wand for this type of energy work. To amplify energy or direct it in a particular way is the main task of the wand and the tool(wand) should match the craft.