The swing of the rest is the size which will rotate above the rest, which lies upon the bed.")[12] from the notion that the work 'swings' from the centre upon which it is mounted. This makes more sense with odd-shaped work but as the lathe is most often used with cylindrical work, it is useful to know the maximum diameter of work the lathe will hold. This is simply the value of the swing (or centre height above the bed) multiplied by two.