This document discusses different types of gears. It begins by introducing gears and their basic functions of transmitting torque and changing speed, torque, and direction of a power source. The document then describes several types of gears: spur gears, helical gears, bevel gears, worm gears, and rack and pinion gears. It also discusses gear trains, how they can reduce speed and increase torque, and the types of simple, compound, and planetary gear trains. Finally, it outlines some key terminology used in describing gears, such as pitch circle, circular pitch, tooth thickness, module, addendum, dedendum, and clearance.

1. Gears
Presented By,
Harshith

2. Content
• Introduction
• Types of Gears
• Gear Trains
• Terminology
• End

3. Introduction
• A gear or cogwheel is a rotating machine part
having cut teeth which mesh with another
toothed part to transmit torque.
• Geared devices can change the speed, torque,
and direction of a power source.
• Two meshed gears always rotate in opposite
directions.
Driven gear Driver gear

4. TYPES OF GEARS
According to the position of axes of the shafts.
a. Parallel
 1.Spur Gear
 2.Helical Gear
 3.Rack and Pinion
b. Intersecting
 Bevel Gear
c. Non-intersecting and Non-parallel
 worm and worm gears

5. SPUR GEAR
Teeth is parallel to axis
of rotation.
Transmit power from
one shaft to another
parallel shaft.
Used in Electric
screwdriver, oscillating
sprinkler, windup alarm
clock, washing machine
and clothes dryer.

6. External and Internal spur Gear

7. Helical Gear
The teeth on helical gears are cut at an angle
to the face of the gear.
This gradual engagement makes helical gears
operate much more smoothly and quietly than
spur gears.
One interesting thing about helical gears is
that if the angles of the gear teeth are correct,
they can be mounted on perpendicular shafts,
adjusting the rotation angle by 90 degrees.

8. Helical Gear

9. Bevel gears
Bevel gears are useful when the direction of a
shaft's rotation needs to be changed.
They are usually mounted on shafts that are 90
degrees apart, but can be designed to work at
other angles as well.
The teeth on bevel gears can be straight, spiral or
hypoid.
locomotives, marine applications, automobiles,
printing presses, cooling towers, power plants,
steel plants, railway track inspection machines,
etc.

10. Straight and Spiral Bevel Gears

11. WORM AND WORM GEAR
Worm gears are used when large gear reductions
are needed. It is common for worm gears to have
reductions of 20:1, and even up to 300:1 or
greater.
Many worm gears have an interesting property
that no other gear set has: the worm can easily
turn the gear, but the gear cannot turn the worm.
Worm gears are used widely in material
handling and transportation machinery,
machine tools, automobiles etc.

12. WORM AND WORM GEAR

13. GEAR TRAINS
A gear train is two or more gear working
together by meshing their teeth and turning
each other in a system to generate power and
speed
It reduces speed and increases torque
Electric motors are used with the gear systems
to reduce the speed and increase the torque.

14. Types of Gear Trains
 Simple gear train
 Compound gear train
 Planetary gear train

15. Simple Gear Train
The most common of the gear train is the gear
pair connecting parallel shafts. The teeth of
this type can be spur, helical or herringbone.
Only one gear may rotate about a single axis

16. Compound Gear Train
• For large velocities,
compound
arrangement is
preferred
• Two or more gears
may rotate about a
single axis
Driver
Compound
Gear
Driven

17. Planetary gear train

18. NOMENCLATURE OF GEARS

19. Pitch circle. This is a theoretical circle on which calculations are
based. Its diameter is called the pitch diameter.

20. Circular pitch. This is the distance from a point on one tooth to the
corresponding point on the adjacent tooth measured along the pitch
circle.

21. Tooth thickness. This is the distance from a point on one face of
tooth to the corresponding point on the adjacent face of the same
tooth measured along the pitch circle.

22. Module. This is the ratio of the pitch diameter to the number ofteeth.
The unit of the module should be millimeters (mm). The module is
defined by the ratio of pitch diameter and number of teeth.

23. Addendum, a. This is the radial distance from the pitch circle to the
outside of the tooth.
Dedendum, b. This is the radial distance from the pitch circle to the
bottom land.

24. Clearance circle. This is a circle that is tangent to the addendum
circle of the mating gear.
Clearance, c. This is the is the amount by which the dedendum ina
given gear exceeds the addendum of its mating gear.

26. Thank You