portion for such refiners has a 30 or 45 degree angle cone e g it is 15 or 22 5 degrees from a cylindrical surface an example of such a conical disc refiner is described in u s pat no 4 283 016 issued aug 11 1981 thus as used herein u201c disc u201d includes u201c conical disc u201d and u201c substantially radially u201d includes the generally outwardly directed but angled gap of a conical refiner the inlet of the outer region of inner ring has a radial transition or close to radial large variation in the radial location of the start of the ground surface normally results in the loss of fiber length when particles larger than the gap are quickly forced into the gap with a long chamfer at the start of the region longer is better the material fed will be gradually reduced in size until small enough coarseness reduction to enter the gap formed by the ground surfaces the groove width of the outer region of the inner ring has to be narrow enough to prevent large unsupported fiber particles from entering the groove and then be forced into the gap thus causing fiber cutting typically the groove width should be no wider than the gap at the inlet of the ground surface subsurface dams or surface dams can be used in order to increase the efficiency of the action and or increase energy input in the inner plates two embodiments of the outer fibrillating ring are shown in fig7 and 8 these can range from high intensity to very low intensity for the purpose of illustration of the concept the pattern of fig7 is a typical example of a high intensity directional outer.