Abstract: A counterweight assembly is especially adapted for mounting to a spinner tool allowing a workpiece to be balanced when rotated during welding or other operations. The counterweight assembly has an adjustable counterweight to provide a necessary amount of counterbalance force depending upon the particular size and configuration of the workpiece. The spinner tool is adapted to secure various diameters of pipe as well as pipe flanges. The spinner tool can be mounted within a portable vise that can be used directly at a work site.