In this paper, an extended accumulative roll bonding (ARB) technique, called the 'Four-Layer Accumulative Roll Bonding (FL-ARB)' technique, is presented for the first time. This technique has been employed to produce ultrafine-grained commercial pure aluminum sheets with success. After three FL-ARB passes, the grain size of pure aluminum was seen to reduce to 380 nm. The bonding strength of the sheets after rolling has also been discussed. Theoretical calculations showed that the bonding strength of sheets processed by the FL-ARB technique can be 2-2.2 times greater than that by the traditional ARB technique. The main advantages of the FL-ARB technique are (a) improvement of the interface bonding, with increasing deformation in each pass, (b) applicability of the technique at room temperature to process most metals, and (c) generation of the largest equivalent strain in the workpiece with the same number of passes, compared with other severe plastic deformation techniques.