Tests on aluminum, copper and brass blanks indicate that, provided proper hold-down methods are used, the limiting drawing ratio that can be obtained is almost independent of type of blank holder. A comparison of theoretical and experimental critical punch loads at failure shows that, for aluminum, good agreement can be obtained when drawing under all-round hydrostatic pressure. This method produces a reduction in die friction and a significant increase in limiting drawing ratio. There is an optimum hydrostatic pressure above which no advantage is to be obtained.

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