What is the meaning of Tommy_bar?

A cylindrical iron or steel bar used as a lever; thus:

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

    A short bar put through the hole in a socket spanner or box spanner to provide leverage.

    A bar used to loosen or tighten some types of chucks and tool holders on machine tools such as lathes or milling machines.

    Source: wiktionary.org