Abstract: Refiner disc segments for use in connection with disc refiners are disclosed. The refiner disc segments include in a radial portion thereof raised bars extending outwardly from the center of the segment with grooves defined between the raised bars, the raised bars having a width B, and the grooves having a width S and a depth D such that the ratio B.multidot.S.multidot.D/S+D is greater than about 2.7 mm and less than about 4.3 mm, and wherein the width B is from about 1 to 4 mm, the width S is from about 2 to 5 mm, and the depth D is from about 1 to 7 mm. Overall refining apparatus including a pair of refining members which includes such refining disc segments are also disclosed as is a method for producing these refining disc segments.