Forging or cold-pressing tool and method of assembling same

A forging or cold-pressing tool comprising a plurality of nib pieces arranged in an annular form in combination, each of the nib pieces having an approximately isosceles trapezoidal cross section, slanting faces at respective opposite ends thereof and a shorter side positioned inwardly of the annular arrangement, and a case having the nib pieces held therein to define a regular polygonal die bore by the nib pieces inside thereof and being used to press a blank, the tool being characterized in that the opposite ends of each nib piece before assembly make an angle .alpha. smaller than an angle obtained by dividing 360.degree. by the number of nib pieces, an outwardly enlarging clearance being created between the pair of nib pieces which are arranged annularly with the shorter sides thereof positioned inside, the nib pieces being elastically deformed by a tightening force of the case when held in the case, whereby the abutting end faces of each pair of adjacent nib pieces are entirely pressed into contact with each other under a pressure increasing from an outer end portion to a portion toward the die bore, and the abutting end faces of the adjacent nib pieces resisting forming therebetween a clearance which would permit the material of the blank to enter between the adjacent contacting nibs.