GEAR CUTTING

BYKHATIK T.R.

SPC Sangola, Dis-Solapur

GEAR MANUFACTURING METHODS

- CASTING

- FORMING

- STAMPING

- POWER METALLURGY

- EXTRUSION

- PLASTING MOLDING

- ROLLING PROCESS

- MACHINING

1] CASTING a) Die casting b) Sand casting c) Investment casting2] FORMING a) Cold Drawing b) Gear Rolling3] Machining processes a. Rotary wheel- milling b. Rotary thred wheel-hobbing c. Rotary/Reciprocating tool-

Gear shapping,broaching

Universal Gear Dividing Head

Types of Dividing Head

1.Plain and simple Dividing Head2.Universal Dividing Head3. Helical Dividing Head4.Optical Dividing Head

Indexing Methods-Definition-Types of Indexing method 1.Direct Indexing method 2.Plain / simple Indexing method 3.Compound Indexing method 4.Differiantial Indexing method 5.Angular Indexing method

1.Direct Indexing• Direct Indexing (Rapid Indexing) is the simplest form of

indexing. Used for quick indexing of work piece. • The direct indexing plate is mounted on the nose of the

dividing head spindle which also carries the work. • The number of divisions required by direct indexing is

limited by the number of holes/slots in the direct indexing plate.

• Direct indexing plates are available with 24, 30 and 36 holes or slots. It is possible to index any number of divisions which is a factor of total holes/slots in the plate

1.Direct Indexing in Universal Dividing Head

• To perform this type of indexing, the worm shaft must be disengaged from the worm gear wheel.

• Since most direct indexing plate have 24 holes, all divisions which are factors of 24 (24, 12, 8, 6, 4, 3, 2) can be produced with this plate.

• Indexing data = N T• N – No. of holes in Indexing Plate• T – No. of required divisions

Example: What is the index movement required to mill 8 slots on a workpiece?

• N T = 24 8 = 3 (3 holes on a 24 hole circle)

1.Direct Indexing

• Whenever starting to machine the first hole, it is necessary to make sure that the indexing pin is in the hole or slot No. Zero or 24 of the indexing plate.

• After doing the necessary indexing movement, it is required to clamp the indexing spindle so that the cutting force will not go onto the indexing plate and indexing pin.

2.Plain Indexing (or) Simple Indexing

• Used for divisions beyond the range of direct indexing

• Universal Dividing Head is used for this• The Indexing plate should be locked with the

body• Worm and worm gear is to be engaged• Dividing head is rotated by turning the index

crank and locked at the next indexed hole on the plate

Plain or Simple Indexing• 40 turns of indexing crank = 1 revolution of index

head spindle• Index plates with concentric circles of holes:

• Plate: 1 - 15, 16, 17, 18, 19, 20• Plate: 2 - 21, 23, 27, 29, 31, 33• Plate: 3 – 37, 39, 41, 43, 47, 49

• Index crank movement = 40/N (N = number of divisions required)

• For cutting 30 teeth, 40/30 = 1 + 1/3 = 1 + 7/21 (One complete turn of indexing crank and 7 holes in 21 hole circle of the index plate)

3.Differential Indexing

• This method is used for divisions that could not be indexed by simple indexing

• The required division is obtained by combination of:– Movement of the index crank similar to simple

indexing– Simultaneous movement of the index plate when

the crank is turned• The rotation of the index plate may be in the

same direction or opposite to the crank rotation

Differential Indexing• Lock pin is disengaged to permit rotation of index

plate• A sleeve with bevel gear is connected to the index

plate• The sleeve and the bevel gear are free to rotate

on the worm shaft• Another bevel gear engages with it and the shaft of that

gear has change gears that mesh with the gear mounted on the back of the main spindle

• Crank rotates the spindle• Spindle’s motion is transmitted to index plate through

change gears

Rule for Differential Indexing1. Gear Ratio = Driving gear/Driven gear

(= Gear on the spindle/Gear on the bevel gear shaft)

=(A-N) X 40/Awhere: N = The required number of divisions to be indexed A = a number nearer to N which can be indexed by plain

indexing (assumed number)

2. Index Crank Movement for each division = 40/A(Index crank is to be moved by this amount for N number of

times for complete division of the work)

Rule for Differential Indexing

3. Number of idlers in the change gears:If (A-N) is positive, the index plate must rotate in the same

direction as the crankIf (A-N) is negative, the index plate must rotate in the

opposite direction to the crankTo achieve the correct direction of rotation, number of idle

gears is obtained as follows:

A-N Simple gear train Compound gear trainPositive One idler No idlerNegative

Two idlers One idler

Rule for Differential Indexing

Change gears with following numbers of teeth are generally supplied:

24, 24, 28, 32, 40, 44, 48, 56, 64, 72, 82, 100

With these gears and the three sets of standard index plates, it is possible to index any number from 1 to 382.

5.Angular Indexing• Angular indexing is the process of dividing the

periphery of a work in angular measurements and not by the number of divisions.

• Indexing method is similar to plain indexing• One complete turn of crank will cause the spindle

and the work to rotate through 360/40 = 9◦• Index crank movement =

Angular displacement in deg/9Angular displacement in minutes/540Angular displacement in seconds/32400

• Gear shaping (pinion cutter)

• Gear planing (Rack cutter)

• Gear hobbing

Gear generating methods

Gear shaping

Gear shaping

Gear shaping

Gear shaping

Gear Planing Rack

Gear Planing with a rack cutter

Gear Planing with a rack cutter

Gear Hobbing

Hobbing is a process of generating a gear using a rotating tool called “Hob”.

The hob has helical threads

The threads have grooves cut parallel to the axis to provide cutting edges.

The gear teeth are cut into the workpiece by a series of cuts made by the hob.

It is the most widely used gear cutting process for creating spur and helical gears.

Gear Hobbing• Gear hobbing is a multipoint machining process in which gear teeth are progressively generated by a series of cuts with a helical cutting tool (hob). 

• Both the hob and the workpiece revolve constantly as the hob is fed across the face width of the gear blank.

• They rotate in a timed relationship

• A proportional feed rate is maintained between the gear blank and the hob

• Several teeth are cut on a progressive basis

• It is used for high production runs

Hobs

Gear Hobbing

Gear Hobbing

Gear Hobbing

Gear Generating comparison

Gear Hobbing

Gear Hobbing

Gear Hobbing

Gear Hobbing

Gear Hobbing

Gear Hobbing

Gear Hobbing

Vertical Hobbing Machine

Vertical Hobbing Machine

Various Gear Cutters

Gear Shaving

Gear Shaving Cutter

Gear Grinding

Gear Grinding