Miter Gears
Miter
gears are a very special type of industrial bevel gear that is specifically
designed for operating in pairs. The unique Miter Gear has a set of tooth
that is identical in number, diametral pitches, and a ratio of 1:1. Miter
Gears are perfectly suited for those applications where torque ratings have
been precisely calculated. For high efficiency, Miter Gears are put to use
as right angle drives. Here motion and power is transmitted between
intersecting shafts at right angles.
Generally Miter Gears are cut at 20 degree pressure angle. The long
addendum system is applied for compensating the tooth undercut in gears &
pinions that has inadequate number of teeth. It must be remembered that
Miter Gears that has only identical number of teeth, pitch and pressure
angle will function together. However, more than two identical miters can be
applied in cases such as differential arrangement.
Installing Miter Gears
For operating with smoothness, without noise and efficiently Miter Gears
need to be properly mounted. Listed here are following points that needs to
be considered for mounting these Gears.
- Mounting at proper angle : Miter gears for a successful
application, and to have a perfect tooth bearing, should be mounted at
90° angle.
- Mounting Distance (MD) to be specified : Mounting Distance is
calculated as the distance from the end point of the hub of a gear to
its corresponding mating gear's center line. Gears that are mounted at
the specified Mounting distance displays a genuine and proper backlash
also the ends of the gear teeth will flush properly with each other.
Let's analyse the problems associated with incorrect Mounting Distance.
Mounting
Distance is less than specified dimension : In this case of
mounting distance of one or both the gears being less than the
specified dimension, the teeth shows a tendency to bind. This also
can lead to an excessive wear or even the damaging consequences like
breakage can also occur. The following drawing illustrates gears
being mounted incorrectly, with a very short Mounting Distance for
one gear.
Mounting
Distance is more than the specified dimension : It is also cause
for concern in cases where Mounting Distance of any of the gear
happens to be longer than the specified dimension. This can also
lead to damaging consequences like the gears not on a full mesh on a
common pitch line. Also the gears may show excessive backlash. Now
this excessive backlash or play, as it is called if not controlled
can lead to sudden impulses or shock load while starting or
reversing. Eventually causing serious damage to the gear tooth. The
following image shows mounting distance which is more than the
specified dimensions.
- Use of Correct Bearings :
All
Miter gears in transmitting power develop radial and axial thrust loads.
This loads must be accommodated by proper use of bearings. Actually the
thrust of Miter Gears can lead to gear separation. It is advised to use
either ball bearings or roller bearings. It is better to give sleeve
bearings a miss. As miter gears are found in cone shape, they generate
axial thrust forces. This is particularly distinct with regard to spiral
miter gears. In this case the thrust's directions changes with the
direction of rotation and the hand of spiral. This is described with the
help of the diagrams.
- Proper Fastening : As the Miter gears generate thrust loads,
the gears, shafts as well as the bearing does show a tendency for
loosening up while in the operation process. That is the reason why
Miter gears should be properly fastened to the shaft. This can be done
with taper pins, keys and set screws, step shafts, etc.
- Correct Tooth Contact : When the Miter gears are assembled in
a proper manner, the contact occurs on both gears just in the middle of
flank and center of face width, somewhat that is near to the toe. An
incorrect tooth contact results in Offset error, Shaft angle error,
Mounting Distance error.
Materials for Miter Gears
There are a variety of materials that can be used for the construction for
Miter gears. Like Plastic, steel etc. While talking of the manufacturing
material Miter Gears can be made by Sintering, Carburizing, Case hardening.
Lets have an in depth look at some of the Miter Gears that are made of Steel
with their usual specifications. These are plain bore gears with hub. These
are some of the examples of specifications and there could be Miter gears
with other specifications also.
16 Pitch Steel Miter Gears with Pressure Angle of 20°
