Soft jaws are one of the simplest methods of customized workholding. Basically, you create an inverted version of your part within the jaws of your vise, and clamp things down.
Workholding is one of the most hot-button issue in the worlds of machining, metalworking, and general fabrication. While finding new ways to hold parts as you cut can be an entertaining endeavor, if you’re on a budget and/or schedule, it will plague your very existence. Vises are one of the primary ways to hold your work, and milling soft jaws to fit specific parts is a common practice.