Abstract:
The definitions
of the normal chordal tooth thickness and the constant chord in
international standard ISO 1122/1-1983(E) are analyzed according
to the basic principle of involute cylindrical gear geometry. It
is pointed out that in the case of spur gears, the two
definitions are respectively identical with generally recognized
traditional formulas, but in the case of helical gears, they are
respectively contradictory with their traditional formulas. The
general principle of the method of the two-point measuring for
the tooth thickness of gears is analysized, and the calculation
formulas of the two-point measuring for the tooth thickness of
the involute helical gear is presented. It is proved
theoretically that a constant chord can be measured with the
method of the two-point measuring (with the tooth thickness
caliper) while normal chordal tooth thickness can not be
measured with the tooth thickness caliper (the method of the
two-point measuring). The issues of the two definitions of the
tooth thickness in the international standard are analysed out
again in measuring.
Key words:
International standard Normal chordal tooth thickness Constant chord Measurement of tooth
thickness
Manuscript received on
January 31, 1994; revised manuscript November 5, 1994
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