A Free Arm machine is also known as a Tubular Bed machine, both are Cylinder Bed machines. The term refers to the bed of the machine being cylindrical rather than Flat Bed in order to allow the ease of sewing narrow or awkward shaped items such as cuffs or trouser legs, or sewing items such as shoes or leather with specialized industrial machines.
In domestic sewing machines, the term 'free arm' denotes a machine which is convertible from flat bed to free arm, with a removable flat area around the tubular bed.
The first non-electric domestic free arm machine was Ward's Arm & Platform patented in 1873, which incorporated a built-in movable table to convert a traditional flat bed machine to free arm. The first electric free arm machine was the Elna No. 1, known colloquially as the Grasshopper. Another example is the Singer 222K, first produced in 1953, which is the free arm version of the 221 Featherweight.