3. Broaching Machine
Broaching is a machining operation in which a tool
usediscalled asbroach havingseriesof cutting teeth.
In this operation broach is either pulled or
pushed with the help of broaching with the
help of broaching machine on the
workpiece.
Parts that is produced by the broaching have good
surfacefinishand dimensionalaccuracy
4. Broach Tool
Broach consist of three sets of cutting teeth.
• Roughing Teeth
• Semi finishing teeth
• Finishing teeth
5. Broach Tool Geometry
Where,
P = Pitch
y = clearance angle,
α = rake angle
RPT = rise of tooth
L = land
R = radius of the gullet
D = depth of the tooth
6. Principle of Broaching
When the broach is fed in a straight line,
metal is cut in several successive layer
with the helpof broach.
The thickness of each layer is same and
called as feed per tooth and sum of the
thickness of all the layers is called asdepth
ofcut.
7. 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.
8. Use of Fixtures
• To located the work in correct positin
• To support and hold the work rigidly during
the operation.
• To guide the broach during the operation.
• To move the the work to correct position
before the start of operation and remove
it after the operation.
9. Specification of Broaching Machine
Power of the motor and its speed
Length of bed
Length of slide stroke
Rated pulling force
Cutting stroke speed
Number of speeds
Return stroke speed
Maximum size of cut
Weight of machine
Size and floor area
10. Types of Broach
Based on type of operation
1. Internal Broach
2. External Broach
Based on Construction
1. Solid Broach
2. Inserted Broach
3. Progressive Broach
Based on Method of operation:
1. Push Broach
2. Pull Broach
Based on Shape of work produced:
1. Key-way Broach
2. Spline Broach
3. Brushing Broach
11. Industrial Broaching Machines
Mainly broaching machines which areusedin
the industriesareof following types:-
Horizontal BroachingMachine
VerticalPullTypeBroachingMachine
Continuous BroachingMachine
RotaryTableBroachingMachine
Surface BroachingMachine
Keyway BroachingMachine
12. Horizontal Broaching Machine
• Horizontal Broaching Machines are capable
of both internal and external surfaces.
• In operation either workpiece is kept
stationery and broach is fed past or broach is
kept stationery and workpiece isfed past.
• This machine has bed similar to the lathe
machine.
• This machine range from 2 to 60 tones and
stroke of 3m for internal broaching
machine and for external broaching machine
it ranges upto 100 tones andstroke of 9m.
14. Vertical Pull type Broaching Machine
• This type of machine are available for both
pullupandpulldown typeof machine.
• This machine is only used for internal
broaching or holebroaching.
• In this machine we can mount more than one
broach.
• In the pull down type the workpiece is
mounted on table and the broach is lowered
to pass its front pilot through the
workpiece.
• In the pull up type, the only difference is
that the ram is provided at the top which
will carrythe broach from bottom to top.
15. Continuous Broaching Machine
• This machine are availableboth in horizontal and verticaltype.
• In this machine the broach remains stationery while the workpiece moves
continuously past.
• In this machine the workpiece are fed past on the chain which is traveling
continuously with the help of sprocketson both the end.
• The chain hasa seriesof fixtureswhich will hold the workpiece.
• In this machine the workpiece is loaded on asideand unloaded on the other side.
16. Rotary Table Broaching Machine
• This machineis also used asa Continuous
BroachingMachine.
• In this machineatable isprovided
which continuously rotates about a
vertical axis.
• On this the fixtures are mounted and
broachisheld tightly on broach holder.
• Theshapeof the broachissameasof the
table.
• Asthe table rotates the workpiecesare
loaded, machined andunloaded.
17. Surface Broaching Machine
• In this machineeither workpieceor broachmovesacrosseachother.
• Thismachinesaregenerallyverticalandhydraulicallyoperated.
• This machine is an alternative to milling machine so machine fixtures are also
usedto hold the workpiece.
• These machines are used for large quantities of workpiece having flat
surfaces.
18. Keyway Broaching Machine
This machine is the simplest type of machine
andit canbeusedfor general purposealso.
If multiple keyways or splines are to be cut
the single broach can be used with the
workpieceandindexedaftereachother.
This machines method is the oldest methods of
all.
20. Maximum load (F) on a Broach
For circular hole:-
F = π .d . T .t . p
Where,
d= diameter of machined hole
T= Total number of teeth cutting at a time
t= Rise per tooth
p= Force required to cut 1mm 2 of metal
at the given rise/tooth for square holes
For square holes:-
F=4l.T.t.P
l=Machined length of one side of the square hole
21. Advantages of Broaching
• Broachhasalongerlifethan other tools.
• Broach canperform roughing and finishing
operations.
• High skilled operator is notrequired.
• Interchangeable components can be
producedat faster rate.
22. Disadvantages of Broaching
• In this process,all jobs needafixture.
• Sharpening of broach is difficult and
expensive.
• With the help of broaching, it is difficult
to produce blindholes.
• Initial cost of broach and broaching
machineisveryhigh.
23. Applications of Broaching
•Theexamplesof components produced
by broaching areasfollows:
• Bearing caps
• Bearingbodies
• Cylinderblocks
• Connectingrods
• Gears andTurbine
• Keyways
• Splines
