Lock Nuts, Screws and Wrenches are essential components to many power tools. Lock nuts and screws can get lost, break, or wear out requiring replacement. It is much cheaper to replace a screw or locknut than it is to replace the entire tool. Specific wrenches are needed for tightening grinding wheels and other parts on tools. If you lose one of these wrenches, your tool is basically useless unless you want to try more dangerous methods of tightening.