1990-1998 Arctic Cat Snowmobiles Repair Manual, Page 18Get this manual
CHAPTER ONE
fasteners jam, the threads are not compatibleA thread pitch gauge (Figure 15) can also be used to determine pitchArctic Cat snowmobiles are manufactured with ISO metric fastenersISO metric threads are cut differently than those of standard American fasteners (Figure 16)Most threads are cut so that the fastener must be turned clockwise to tighten itThese are called right-hand threadsSome fasteners have lefthand threads and must be turned counterclockwise to be tightenedLeft-hand threads are used in locations where normal rotation of the equipment would tend to loosen right-hand threaded fastener
is used mainly on machine parts and not for fastenersIt is also used on all metric thread spark plugsISO metric threads are specified by the capital letter followed by the diameter in millimeters and the pitch (or the distance between each thread) in millimeters separated by the sign "x"For example M8 1.25 bolt is one that has diameter of millimeters with distance of 125 millimeters between each threadThe measurement across two flats on the head of the bolt (Figure 11) indicates the proper wrench size to be used, but it is not an indication of thread sizeFigure 13 shows how to determine bolt diameter