Working with brass or wood often generates a very fine dust that can work its way into the toggle switch, eventually causing the possibility of the speed control working erratically or even shorting out. This special nut with a built-in seal replaces the standard mounting collar nut on the speed control on/off switch. The soft silicon collar slips over the head and shaft of the toggle switch and seals out fine dust to keep the inside of the switch as clean as new for years of reliable operation. This is an easy and inexpensive way to avoid possible headaches later on.
Always wear safety glasses when operating machine tools.