tommy bar

noun3

1. •
   A cylindrical iron or steel bar used as a lever.
2. •
   A short bar put through the hole in a socket spanner or box spanner to provide leverage.
3. •
   A bar used to loosen or tighten some types of chucks and tool holders on machine tools such as lathes or milling machines.

   • A set of two tommy bars is the standard tooling for the spindle nose threads of some minilathes and minimills.