Screw Threads - Arctic Cat Cougar Service Manual

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fasteners jam, the threads are not compatible. A
thread pitch gauge (Figure 15) can also be used
to determine pitch. Arctic Cat snowmobiles are
manufactured with ISO metric fasteners. ISO
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 it. These are called
right-hand threads. Some fasteners have left-
hand threads and must be turned counterclock-
wise to be tightened. Left-hand threads are used
in locations where normal rotation of the equip-
ment would tend to loosen a right-hand threaded
fastener.
ISO Metric Screw Threads
ISO (International Organization for Stand-
ardization) metric threads come in coarse, fine
and constant pitch threads. The ISO coarse pitch
is used for most common fastener applications.
The fine pitch thread is used on certain precision
tools and instruments. The constant pitch thread
CHAPTER ONE
is used mainly on machine parts and not for
fasteners. It is also used on all metric thread spark
plugs.
ISO metric threads are specified by the capital
letter M followed by the diameter in millimeters
and the pitch (or the distance between each
thread) in millimeters separated by the sign "x".
For example a M8 x 1.25 bolt is one that has a
diameter of 8 millimeters with a distance of 125
millimeters between each thread. The measure-
ment 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 size.
Figure 13 shows how to determine bolt diameter.
American Threads
American threads come in a coarse or fine
thread. Because both coarse and fine threads are
used for general use, it is important to match the
threads correctly so you do not strip the threads
and damage one or both fasteners.
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Hex Flat Oval Fillister
Round
MACHINE SCREWS
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Slotted Phillips
Allen Fluted (splined)
OPENINGS FOR TURNING TOOLS