What do you do if, during an operation, you drop a chuck key and there is no replacement? In emergencies, it is possible to tighten the chuck using what is to hand. Put an instrument such as the tip of a Trethowan bone lever or Steinmann pin in the round hole on the chuck that receives the chuck key. Choose a periosteal elevator, old osteotome or flat-headed screwdriver; engage this in the gear face of the chuck and lever against the Trethowan to tighten the chuck.
Figure 1.
Emergency technique to tighten a Jacob's chuck.