fig1 shows only one half of a press roll according to the present invention , where the other half is a mirror image of the shown half . the press roll comprises an axial core 102 in the form of a central drum 102 , to the outer ends of which attachment means 104 are attached for pivotally mounting the press roll in a roll press . several supporting ribs 106 , which extend along the longitudinal extension of the axial core 102 and extend in a substantially radial direction , are welded to the outer surface of the central drum 102 . the supporting ribs 106 are distributed around the circumference of the central drum 102 . the mantle section is shrunk onto these supporting ribs 106 in a conventional manner . sixteen perforated roll plates 108 are attached to the mantle section , of which only eight are shown in the figure , and each roll plate 108 extends around the entire circumference of the press roll . the short sides of each roll plate 108 , which meet in a transverse joint 110 , have been welded to each other , after which the roll plate 108 has been slipped onto the mantle section and shrunk into position by cooling , so that it abuts against the mantle section . in this embodiment , each roll plate 108 comprises three mounting openings 112 , where the position of only one mounting opening 112 per roll plate 108 is shown in the figure . the mounting openings 112 are distributed between the two short sides of the roll plate 108 along the longitudinal extension of the roll plate 108 and the circumference of the press roll . as shown in the figure , the mounting openings 112 are located along the longitudinal centre line 114 of the roll plate 108 . fig2 shows a section of the press roll of fig1 along line g - g , and an enlarged view of a mounting opening 202 with an associated attachment hole 204 and fixing pin 206 . here , the mantle section of the press roll is more clearly shown . the mantle section comprises several frame rings 208 distributed along the length of the central drum 102 and several flat bars 210 which extend along the longitudinal extension of the central drum 102 and are distributed around the circumference of the press roll . the frame rings 208 are attached to the supporting ribs 106 by way of the flat bars 210 . the roll plates 108 abut against the frame rings 208 . the roll plate 108 comprises three drilled mounting openings , 112 , 202 and 212 , and the mantle section comprises three attachment holes , 204 , 214 and 216 , which are drilled in one frame ring 208 . each attachment hole , 204 , 214 and 216 , extends along the same radius along which each mounting opening , 112 , 202 and 212 , extends , whereby each attachment hole 204 , 214 and 216 , is radially aligned with its mounting opening 112 , 202 , 212 . a fixing pin 206 is received in each mounting opening 112 , 202 and 212 , and attachment hole 204 , 214 and 216 , which fixing pin 206 is anchored in the frame ring 208 and is surrounded by the inner surface of its mounting opening , 112 , 202 and 212 , whereby a locking of the roll plate 108 to the mantle section is obtained . each mounting opening 112 , 202 and 212 , and its attachment hole 204 , 214 and 216 , are radially aligned with a supporting rib 106 , which provides an effective rigidity when drilling the mounting openings 112 , 202 and 212 , and attachment holes 204 , 214 and 216 . the pairs of mounting openings 112 , 202 and 212 , and the attachment holes 204 , 214 and 216 , are evenly distributed around the entire circumference of the press roll so that the distance between two mounting openings 112 , 202 and 212 , which are adjacent to each other in the circumferential direction of the press roll , is substantially equal around the entire circumference of the press roll . here , two mounting openings , 112 , 202 and 212 , which are adjacent to each other in the circumferential direction of the press roll , are spaced apart by about 120 ° in the cross - section of the roll press . here , each attachment hole has a smaller diameter than each mounting opening . the surfaces of the roll plate , where each mounting opening 112 , 202 and 212 , is provided , have no perforation . fig3 shows a section of an embodiment of the fixing pin 206 according to the present invention , having a diameter which is a bit larger than the diameter of the attachment hole . the fixing pin 206 is made from the alloy 254smo and is provided with a fixing portion 301 for anchorage in an attachment hole , the fixing portion 301 being provided with at least one thread . the threaded fixing portion 301 is driven into an attachment hole through the associated mounting opening as described in connection with fig4 . the diameter of the fixing pin 206 is smaller than the diameter of the mounting opening , whereby a gap is provided between the fixing pin 206 and the inner surface of its mounting opening , and potential damage to the roll plate when driving the fixing pin 206 is avoided . further advantages with this gap are disclosed in connection with fig4 . fig4 shows a flow chart illustrating an embodiment of the method when manufacturing a press roll for washing and / or dewatering pulp according to the present invention , where the press roll comprises an axial core and a mantle section provided around the axial core , to which mantle section several perforated roll plates are intended to be attached , which method comprises the following steps : a roll plate is heated to about 250 to 300 ° c ., at 401 , so it thermally expands and , inter alia , is lengthened , and is placed around the frame rings of the mantle section , at 402 , so that the long sides of the roll plate extend along the entire circumference of the press roll . the heated roll plate , which surrounds the mantle section , is now “ hanging down ” on the underside of the press roll . the roll plate is cooled , at 403 , whereby the roll plate , which is provided onto the mantle section , is shrunk into firm engagement with and around the frame rings of the mantle section , and a so called “ shrink fit ” is attained . in the same step , at 404 , a first mounting opening is drilled in the roll plate , between the two short sides of the roll plate along the longitudinal center line of the roll plate , and a first attachment hole is drilled in a frame ring of the mantle section . this drilling is performed by a drill having two different diameters , so that the attachment hole obtains a smaller diameter than the diameter of the mounting opening . the drilling is performed so that the mounting opening and the associated attachment hole are radially aligned with a supporting rib attached to the axial core of the press roll . subsequently , the press roll is rotated about 60 ° in relation to the drill , at 405 , and the drilling step is repeated , at 404 , so that a second mounting opening is provided in the roll plate and as second attachment hole is provided in the frame ring of the mantle section . said rotation , 405 , and drilling , 404 , are repeated until the number of mounting openings and attachment holes drilled , respectively , is six . in this manner , the mounting openings are evenly distributed around the entire circumference of the press roll so that the distance between two mounting openings , which are adjacent to each other in the circumferential direction of the press roll , is substantially equal around the entire circumference of the press roll . a first fixing pin is provided with a fixing portion , at 406 , comprising at least one thread , and the first fixing pin is driven into the first attachment hole , at 407 , through the first mounting opening , whereby an effective anchoring of the fixing pin is attained . subsequently , a second fixing pin is provided with a fixing portion , at 406 , comprising at least one thread , and is driven into the second attachment hole , at 407 , through the first mounting opening , in the same manner . this is repeated until the number of driven fixing pin is six , and all six pairs of mounting openings and attachment holes are provided with a fixing pin . additionally , each fixing pin has been given such a longitudinal extension in relation to each attachment hole and mounting opening that the fixing pin is surrounded by the inner surface of the mounting opening without rising above the outer surface of the roll plate . further , the diameter of every fixing pin is smaller than the diameter of its mounting opening , whereby a gap is provided between the fixing pin and the inner surface of its mounting surface . this gap enables a visual inspection to see if the roll plate has been dislocated during the assembly and / or during operation . the gap also provides for a play which is advantageous since the roll plate expands and contracts . if a further roll plate is to be mounted , the steps 401 to 407 are repeated , and when all roll plates are mounted , the press roll can be mounted in a roll press , at 408 . when repairing a press roll , because one of the roll plates is damaged , the damaged roll plate is removed , after which the steps 401 to 407 are performed as mentioned above . fig5 shows an embodiment of the roll press for washing and / or dewatering pulp according to the present invention , comprising a first press roll 502 and a second roll press 504 of the kind shown in fig1 . the longitudinal central axes of the press rolls , 502 and 504 , lie in substantially the same horizontal plane . the pulp is received through an inlet 506 and is pushed up towards the press nip 408 between the first and second press rolls , 502 and 504 . the direction of rotation of each press roll 502 , 504 is illustrated by way of vertical arrows in the figure . the pulp passes the press nip 508 in a vertical direction , from below upwards , where the pulp is dewatered and is pushed further up in a vertical direction . other embodiments of the roll press according to the present invention are also possible . the longitudinal central axes of the press rolls can for example lie in substantially the same vertical plane , etc . although the invention herein has been described with reference to particular embodiments , it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention . it is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims .