greater adhesion between fibers which results in stronger paper on the other hand shorter paper fibers means less total surface area per fiber shortened fibers bond with fewer other fibers than do long fibers and the paper formed from the shortened fibers is of reduced strength in addition fiber fragments that are rendered too small are not retained on the forming wire of a papermaking machine and are thus lost as sludge the dull edged refiner bars 76 78 result in a loss of fiber and an increased cost of manufacturing paper from a given fiber stock along with the additional detriment of producing a weaker paper the refining mechanism of sharp edge bars 70 72 is not completely understood but it is thought that the sharp edges staple or hold the fibers in place as the refining action takes place in practice it has been found difficult to maintain truly sharp edges as the refiner bars 66 68 are subject to wear in actual use a number of techniques for causing the bars to wear sharp have been developed fig1 illustrates an alternative approach to holding fibers 94 by the employment of rough edges 90 92 on bars 86 88 thus the provision of rough edges on refiner bars can facilitate the fibrillation of wood pulp fibers in addition rough edged bars which require a less distinctly sharp edge may be more readily obtained fig7 shows a refiner bar 96 in cross section the.