Abstract: A chuck key holder is arranged on a power supply means and rotatably carries a chuck key for adjusting the clamping jaws of a chuck on an electrically or pneumatically driven machine provided with the chuck, e.g. a hand-held drilling machine. The holder includes a channel for accommodating the lead and a mounting for the chuck key. The holder consists of a basic structure made up from two identically alike basic parts (11, 12), of which one (11) is turned 180.degree. in relation to the other (12). In either basic part (11, 12) there is formed one half of the channel for the lead (15) and one half of the key mounting (16). Fastening means (21, 22) are arranged to keep the basic parts (11, 12) together.