Many engineers incorporating lead screws in motion control devices have gotten used to calling Tom Solon, an applications engineer for Kerk Motion Products Inc., for advice. But at least one company has found a new reason to call him: to get his help in a lawsuit. Solon is getting ready to testify as an expert witness in an upcoming patent-infringement suit involving the design of some processing equipment used in the semiconductor industry. "I got the call because of my background in the industry," he says. The mechanical engineer, who has his Professional Engineers license, used to work at Digital Equipment Corp. Is this another career path for Solon? "I like the occasional involvement," he says, "but I'm not giving up my day job for this."