Mechanical term for a central rotating rod or spindle that transmits motion or supports parts. 心棒 is the core shaft inside a machine or device.
この機械の心棒が曲がってしまった。
The shaft of this machine has bent.
central figure; core member; linchpin
Figurative use for a person who is the central pillar or driving force of a group or organization.
彼はチームの心棒として活躍している。
He is active as the central figure of the team.
旋盤の心棒に材料を取り付ける。
Attach the material to the lathe's mandrel.
あの人が会社の心棒だ。
That person is the linchpin of the company.
Compound of 心 (しん, 'core, heart') and 棒 (ぼう, 'rod, stick'). The literal meaning is 'core rod', which developed into the mechanical sense of a central shaft and later the figurative sense of a central person.