masse surfacique de base

OBS: grammage : Dans le domaine du papier, ce terme est défini dans le Grand dict. encycl. Larousse comme la «Masse par unité de surface d'un papier ou d'un carton, qui est exprimée en grammes par mètre carré.» Syn. «masse au mètre carré». C'est une définition qui correspond bien à la notion de cette fiche, mais nous n'avons pas été en mesure de confirmer que ce terme est aussi utilisé dans le domaine de la métallurgie. Voir aussi «base box» (ou «basis box») dans TERMIUM.

CONT: Tin plate is now sold both on a weight per unit area basis and on a thickness basis. The old unit of area is the base box, equal to the area of 112 sheets, 14 by 20 inches, or 31 360 square inches (217.78 square feet). The new unit of thickness is the millimetre and the corresponding area designation for pricing and weight or area calculations is the SITA (System International Tin Plate Area) which equals 100 square metres or 4.9426 base boxes. ... The use of symbols to designate gage was displaced by the use of base weights (or basis weights) expressed in pounds per base box that also indicated the approximate thickness of the tin-mill product ... With the recent introduction of the metric system (SI) in production, gage is the basic unit for specification and area becomes only a derived value for commercial usage.
CONT: The thickness of lighter gauge carbon steels, 0.38 mm, sometimes referred to as tin mill black plate, employed as a base metal for terne plate is expressed by base weight method. 107, 135 and 155 pounds per single base box sizes are most common. They are also known as 1C, 1X and 2X respectively.