HELICAL GEAR

Elements of teeth are twisted or helical.

Used for connecting shaft at an angle in same or different planes.

Smooth acting gearing.

MITRE GEARING

When the shafts are at 90º and two bevel gears are of same size, known as “miter gears”.

SPUR GEAR

Teeth element parallel to rotating shafts are known as spur gear.

Used to transmit power and motion through parallel shafts.

HERRINGBONE GEAR

It’s equivalent to two helical gears,one having a right hand and other a left hand helix.

It’s used in heavy duty machines like steel roll mills.

BEVEL GEAR

When two shafts are in same plane but at another,bevel gears an angle with one are used.

It’s a frustum of a cone having all elements of teeth intersecting at a point.

DIRECTION OF ROTATION OF CUTTER

Down milling Direction of rotation

of cutter and work piece feed in same direction.

METHOD OF MOUNTING THE CUTTER

Arbor type cutter. Cutter mounted on

arbor and arbor size selected as per cutter bore size.

DIRECTION OF HELIX OF CUTTER

Cutter axis is held vertically and the helix is towards the right side is called a right hand helix cutter.

DIRECTION OF HELIX OF

CUTTER

Helix is towards the left side ,it is called a left hand helix cutter.

DIRECTION OF HELIX OF CUTTER

When a cutter has a helix and a cut of the same hand,this force will pull the cutter away form the spindle.

HYPOID GEARS

Modification of a bevel gear where the shaft are at right angle but they don’t intersect as do the shaft for bevel gears.

RACK GEARS

Rack gears are straight and have no curvature.

Used for feeding mechanism and reciprocating drives.

BASIC ELEMENTS OF SPUR GEAR

Pitch circle. Circular pitch. Pitch circle diameter. Addendum circle. Root circle. Addendum. Dedendum . Hand. Clearance. Working depth. Flank of tooth.

BASIC ELEMENTS OF SPURGEAR

Diametral pitch. Pressure angle

WORM GEAR

When a large speed reduction is desired worm gear are used.

Worm will always be the driver & used for teeth mechanism.s

ANNULAR GEAR

A gear with internal teeth is known as annular gear are used in automobiles.

CLERANCE ANGLE

This is the clearance or relief provided behind the cutting edge.

It prevents rubbing as well, thus reducing cutting force.

RAKE ANGLE

Angle given in front of the leading edge of tool.

It’s reduce the pressure of the chip on the tool face.

Positive rake angles produce better finish at low speeds.

RAKE ANGLE

Zero and negative rake angle tools are stronger and have a long tool life.