TYPES OF GEARS

 Helical Gear • Helical gears have their teeth inclined to the axis of the shafts in the form of a helix. • Helical gears can take higher loads than similarly sized spur gears. The motion of helical gears is smoother and quieter than the motion of spur gears. • The angle of the helix on both the gear must be same in magnitude but opposite in direction, i.e., a right hand pinion meshes with a left hand gear. • These gears are usually considered as high speed gears. 

 Herringbone Gear • Herringbone gears resemble two helical gears that have been placed side by side. • A disadvantage of the herringbone gear is that it cannot be cut by simple gear hobbing machines. • Herringbone is usually referred to as Double helical gear but the fact is that Herringbone is type of double gear with two helical gears joined together correctly of opposite helix and they don't have any clearance between them, whereas in double helical gear there is a groove between the two helical gear given for tool run out for manufacturing. 

Worm Gear • Worm gears are used to transmit power at 90° and where high reductions are required. • In worm gears, one gear has screw threads. Due to this, worm gears are quiet, vibration free and give a smooth output. • Worm gears and worm gear shafts are almost invariably at right angles. 

. Rack and Pinion • A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely large radius of curvature. Pinion can be considered as a spur gear. • Torque can be converted to linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line. • Such a mechanism is used in automobiles to convert the rotation of the steeing wheel into the left-to-right motion of the tie rod(s). 

 Internal and External Gear Internal Gear • An internal gear is one with the teeth formed on the inner surface of a cylinder or cone. External Gear • An external gear is one with the teeth formed on the outer surface of a cylinder or cone. 

Face Gear • Face gears transmit power at (usually) right angles in a circular motion. • Face gears are not very common in industrial application. 

Sprockets • Sprockets are used to run chains or belts. They are typically used in conveyor systems. • They are used in chain drives, in motorcycles and bicycles.