•Cutting tool used in this process is known as “BROACH”.

•Broach is a tapered tool on which teeth are cut.

•Material is removed by pushing or pulling action of tool.

•Material with C40 rockwell hardness can be machined.

•Key ways, splines, clutch plates etc can be machined by broaching.

•Work piece is fixed on fixture and broach is pulled or pushed. Sharp edges of broach penetrate into work piece and due to shearing action plastic deformation of workpiece takes place and metal removes in form of chips.

• Thickness of chip is approximately half the pitch. Chips are collected in to chip space and it is removed when broach comes out from workpiece.

Principle of working:

• Constructional Features:

1)Work holding fixture

2)Broaching tool

3)Drive Mechanism

4)Supporting frame.

1) Work holding fixture• Used to hold work piece in proper

position

• Some times it guides tools

• It is also used to rotate work piece in cutting of helical gear.

• Three types of fixtures-Manual, semi automatic, automatic.

• Manual fixtures are used for small batches,

• Hydraulic and Pneumatic type semi automatic or automatic fixtures are used in mass production

2) Broach ToolClassification:

• According to type of cut: -External broach

-Internal broach

2) According to method of cutting:-Push broach

-Pull broach

3) According to shape: -Solid broach

-Inserted broach

-Progressive broach

4) According to application: -Keyway broach

-Spline broach

-Helical cut broach

2) Broach ToolClassification:

Internal broach: Used to increase hole size and finishing

External broach: Used to make external shapes. Small segments are arranged in row in one piece.

Push broach: It is pushed in work piece to remove material. It is having small length to reduce possibility of bending of tool

Pull broach: Material is removed by pulling action of broach from work piece.

Solid broach: It is made from single bar stock. It has high dimensional accuracy. Entire broach is replaced in case of wear of teeth.

Inserted broach: It is made of tool holder and inserts of HSS, carbides etc. Inserts are brazed on tool holder.

Progressive broach: It is used for wide surfaces. Two pairs of rough teeth and finish teeth are used. Surface is machined in one pass.

Nomenclature of broach:

Nomenclature of broach:

Pull End: It is provided in pull broach to attach pulling mechanism.

Front pilot: It guides broach in hole and also works as rough no-go gauge.

Rear pilot: It determines size of finished hole.

Follower diameter: It is held in automatic machine in order bring in original position.

Shank length: It is length to pass from work piece and attach puller before roughing teeth engage with work piece.

Nomenclature of broach:

Rough teeth: It removes major material.

Semi finish teeth: Provides smoothness while cutting

Finishing teeth: They are of same height. Provides finishing to work piece.

Land: It is upper most portion of tooth.

Back off angle: Also known as clearance or relief angle. It prevents rubbing of land. Angle is between 0.50 to 3o.

Face angle: Also known as hook angle. It can be compared with rake angle of single point tool. Angle is between 150 to 200.

Nomenclature of broach:

Tooth gullet: Chip space between two tooth of tool.

Pitch: Distance between same point on two successive teeth.

Chip breaker:Prevents collection of chip3) Drive Mechanism:

Mechanical(Screw & Nut), Hydraulic or Pneumatic drives are used to provide reciprocating motion.

4) Supporting Frame:

Casted heavy part of machine which supports various parts of machine.

Types of broaching machinesA)According to direction of broach travel.

1) Horizontal broaching machine2) Vertical broaching machine

B)According to Method of operation.1) Pull broaching machine2) Push broaching machine3) Surface broaching machine4) Continuous broaching machine

C)According to Method of drive.1) Mechanical Drive machine2) Pneumatic drive machine3) Hydraulic drive machine

D)According to type of operation.1) External broaching machine2) Internal broaching machine

1) Horizontal broaching machine.

• Usually pull type.

• Used for internal and external broaching.

• Bed is approximately double size than broach stroke

• Ram is hydraulically operated.

• Used to make keyways, splines, slots etc.

2)Vertical Broaching machine• It can be push type or pull type.

• Broach is held vertically.

• 2,4,6 broaches can be operated at time.

• Stroke height is limited upto 1500mm.

• Less space is required compared to horizontal machine.

• Hydraulic or electromechanical drives can be used.

• Preferable for mass production

3)Continuous broaching machine

• Used for mass production of small work pieces.

• Rotary or Horizontal type of movement can be provided.

• In rotary machine, rotary table is used. W/P is indexed and broaching is done.

• In horizontal machine, conveyer continuously moves and broach remains steady.

Advantages of broaching:1)High production rate.2)Job is prepared in one stroke3)High tool life4)Internal and external machining can be done5)0.8micron finishing can be obtained6)Interchangeability of components can be done due to tolerances obtained in range.7)Roughing and finishing can be done in single stroke

Limitations of broaching:1)Costly tool2)Not suitable for small batch.3)Less amount of material is removed4)Proper fixtures are required.5)Strains are produced in w/p6)Surfaces should be parallel to broach travel axis.