Extrusion die for semi-hollow and hollow extruded shapes and tube

An extrusion die for use in producing aluminum alloy articles of extruded shapes or tube having a void with defined internal dimension, said die comprising:

• i) a die plate with at least one die cavity defined by a first die bearing surface which defines an external shape for such extruded article;
• ii) an extruding mandrel secured in said die cavity and having a second die bearing surface which defines an internal shape for such extruded void, said second die bearing surface opposing said first die bearing surface;
• iii) a truing mandrel positioned beyond said mandrel second die bearing surface for correcting internal shape of such void and providing such defined internal dimension, said truing mandrel having a forming surface defining an external dimension relative to an external dimension of said extruding mandrel for correcting of internal shape where said truing mandrel external dimension is at least equal to a lower limit for finish tolerance on such internal dimension, said truing mandrel forming surface being spaced from said extruding mandrel bearing surface by a reduced portion and having an internal dimension equal to or greater than said external dimension of said second die bearing surface;
• iv) said extruding mandrel bearing surface, by virtue of said truing mandrel, being shorter than a normal extruding mandrel bearing surface to provide an extruded shape or tube with better tolerance while extruding at higher speeds with less temperature build up at said extrusion die.