(57) In the wall of the tin body grooves are introduced between tools radially movable
in opposite senses towards the tin body, one tool being provided with ridges and the
other with grooves registering with the ridges. This method makes it possible, contrary
to the usual rollers, to introduce grooves with fairly small tolerances. Damage of
the lacquer does not occur. Because of the forming of sharper grooves the radial strength
will be improved and the wall thickness of the tin body can be reduced.
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