- Before we begin going
into our driving equations and modeling our gear.
Let's go over some common gear nomenclature.
The module is the measure
of the gear tooth size and the metric system.
The diametrical pitch is the measure
of the gear tooth size and the Imperial or inch system.
And it's the number of teeth
in the gear per inch of its pitch diameter.
The number of teeth is simply the number
of teeth in the gear, and it's used to calculate the module
or the diametrical pitch, depending
on which system you're working with.
The center point distance is simply the distance
between the centers of two mating gears.
The pitch diameter circle is an imaginary circle that passes
through the teeth of a gear wheel.
The pitch diameter is tangent
to the meeting gears pitch diameter.
At the pitch point, the pitch point is the point
of contact between two mating gears
at their respective pitch diameters.
The pressure angle is the angle
at the pitch point between the line
of action and the plane tangent to the tooth's surface.
The standard pressure angle today is 20 degrees though
some older gears will have a pressure angle of 14.5 degrees.
The root diameter is simply the diameter
at the base of the tooth.
The outside diameter is the overall diameter of the gear.
The circular pitch is the distance from one point
on one tooth to a corresponding point on the adjacent tooth
and it's measured
along the circumference at the pitch diameter.
So as you see here, it's measuring the point
on the back face of one tooth, and then subsequently going
to the point on the next tooth in the same location.
The circular tooth thickness is the thickness
of the tooth measured
along the circumference of the pitch diameter.
So the distance would actually be in arc length.
The dedendum is the distance
between the root diameter and the pitch diameter.
The addendum is the distance
between the outer diameter and the pitch diameter.
And finally backlash is the clearance
between mating gear teeth
and it used to help prevent gear tooth wear and binding.
Now that we've gone over our gear nomenclature
we're ready to start going into our gear equations.