Abstract: To be able, in a machine for machining workpieces and showing a spindle with spindle draw bar, to use an arm (10) with a draw bar pin (2) in a machining device for several working operations or separate tool holders (3) or different types of tools, the draw bar pin (2) is arranged in one piece with or in communication with a tool element (4) including in the arm (10). The tool element is shaped to hold tools or the tool holder (3). The draw bar pin (2) and tool element (4) plus eventual existing connecting elements (5, 12, 13) between the draw bar pin and the tool element are arranged displaceable in the arm (10), whereby the draw bar force of the machine's spindle draw bar is utilized to retain the tools or tool holder in the arm.