Metric Standards
Metric roller chain and sprockets are classified according to ISO
standards 606. The number correlates to pitch in 1/16" increments,
expressed in millimeter units. An ISO 12 sprocket mates with a chain
with ¾" or 19.05mm, pitch. Number of teeth for a specified
pitch will determine sprocket size and drive ratio.
The SAE Aerospace Standard (AS) establishes the standard modules for
aerospace metric involute gear teeth and establishes the tooth
dimensions of aerospace metric involute gear teeth in terms of the
conjugate rack type cutter whose counterpart reference profile is called
the basic rack profile of the generated gear, having the tooth
dimensions expressed in terms proportional to the module.
SAE also covers established metric manufacturing tolerances applicable
to corrosion and heat resistant steel, iron alloy, titanium and titanium
alloy bars and wire ordered to metric dimension.
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