Hi all, I use a similar tool at work, measures chain stretch on forklift mast chains, it has a wear limit marked on it to indicate 3%, thats the limit on mast chains, different settings for the different chain types AL & BL, these chains are quite different to bike chians in that they donot allow for teeth, they are just bunch of sideplates pinned together, mainly 6 plates starting at 1" pitch and going up, JFYI........regards wayne davidson Invers NZ......