On previous sections we have examined how chain pins can break, erode, gall, corrode or bend sue to adverse operational conditions. In other more unusual circumstances pins may shear. If pin shear occurs it can normally be traced to a sudden, abnormally sever overload. Accidental jam ups can be seen as a likely cause. In the case of the pins illustrated a sudden shock load occurred where the chain was already running heavily loaded causing pin shear.
Pin shear is characterised by a rounded, reasonably smooth cross sectional surface as illustrated in fig. 21.7.1, shearing occurs at the points highlighted in diagram 21.7.2. As the pin shear can normally be traced to an abnormal load condition the cause can usually be determined and if re-occurrence is considered likely thereafter remedied.