Abstract: A tool for use in a can closing or seaming machine to adjust the spring pressure exerted by the can holding chuck spring is disclosed. The tool permits chuck spring adjustment in conjunction with a force gage in situ without necessitating the removal of the gage from the machine for each spring incremental adjustment as is necessary in the prior art. The tool is a self-contained unit which includes an axially guidable and turnable wrench member, the tool also serving as an adapter or spacer for positioning the force gage in the machine.