Abstract: In a device for the automatic forming of packs of trimmed metal sheets for armatures of electrical machinery or the like, the pack (P') is formed by the controlled drop of a sheet stack (P) housed in a tubular magazine (1) open at the bottom. The pack is dropped against an underlying collection bottom (2) which is brought to a predefined distance from the lower end of the magazine (1). A tightening clamp (3,4) at the lower end of the magazine (1) blocks the stack (P) against a further gravity drop after its descent against the collection bottom (2). A subsequent first lowering of the bottom (2) to separate the pack (P') from the overlying stack, by virtue of a detachment device (22, 122), is followed by a detachment from the lower sheet (L') of the stack (P) of a possible sheet (L) which is mistakenly and temporarily held against the lower sheet (L') of the stack (P) but belongs to the overlying pack (P').