PURPOSE: To tightly fit the inside wall of a can lid and the outside wall of a can barrel by providing an outer flange to the mouth edge of the can barrel, coiling the same to the outer side, reducing the can mouth in such a manner that the outside diameter of the can barrel becomes equal to the outside diameter of the coiled part and providing an annular convex flight to the upper part of the can barrel wall.

CONSTITUTION: An external coiled part is provided to the mouth of a large-size square can. In order to tightly fit a can lid, an outward flange 2 is provided to the top mouth edge of a can barrel 1 and this is coiled outward by a coiling machine to form a tubular edge 3. The mouth part is drawn until the outside wall of the tubular edge 3 and the outside wall of the can barrel becomes flush to provide an annular convex flight 5 to the upper part of the can barrel. In this case, the (b) part between the side wall (a) part and the tubular edge 3 slightly elongates but there is no likelihood of producing any crease on the outside wall of the mouth and the drawn mouth part with the tubular edge 3 is smoothly and readily formed. The distance (d) between the outside walls of the tubular edge 3 is made nearly the same as the distance (d1) between the outside walls of the can barrel, and therefore if the outer lid is put on, its inside wall makes tight fitting to the outside wall of the tubular edge 3 and the outside wall of the can barrel.