METAL CUTTING,BROACHING AND SAWING MACHINE,MANUFACTURING PROCESSES,PRODUCTION TECHNOLOGY

1. Prof. Mayur S Modi
Assistant Professor
Mechanical Engineering Department
SSASIT, Surat
Sawing & BroachingSawing & Broaching
MachinesMachines
Manufacturing processes- I
(131903)

2. Broaching
• Broaching is the process of removing metal with
a tool which has “teeth” arranged in a row. Each
tooth is successively higher than the previous
tooth and removes more material.
• In broaching, one stroke or cycle of the machine
produces a finished part(UP TO 6mm).
• Broaching is used to produce both internal and
external features.
• Production rates are high and tolerances of +/- .
0005” are possible.

3. Broaching

4. Broaching

5. Broaching

7. Terminology of broach

9. Chipbreakers and a Broaching Machine
Fig : Chipbreaker features on (a) a flat broach and (b) a round broach. (c) Vertical broaching
machine.

10. Broaching
• Chip Formation
• Chip formation involves three basic requirements:
• The cutting tool must be harder than the
part material
• There must be interference between the tool
and the part as designated by the feed rate
and cut per tooth.
• There must be a relative motion or cutting
velocity between the tool and work piece
with sufficient force to overcome the
resistance of the part material.

11. Broaching
Tool Feed Direction
Gullet
Workpiece
Depth of
cut per tooth
Tool

12. Broaching
• Chip Formation
• As long as these three conditions exist, the portion of
the material being machined that interferes with the
free passage of the tool will be displaced to create a
chip.
• Many combinations exist that may fulfill such
requirements.
• Variations in tool material and tool geometry, feed
and depth of cut, cutting velocity, and part material
have an effect not only upon the formation of the
chip, but also upon cutting force, cutting
horsepower, cutting temperatures, tool wear and
tool life, dimensional stability, and the quality of
the newly created surface.

13. Broaching
• The Mechanics of Chip Formation
• Empirical metal-cutting studies reveal several important
characteristics of the chips formed during the broaching
process:
• The cutting process generates heat
• The thickness of the chip is usually greater than the thickness
of the layer from which it came
• The hardness of the chip is usually much greater than the
hardness of the parent material, and
• The other three relative values are all affected by changes in
cutting conditions and in properties of the material to be
machined

14. Broaching
• The Mechanics of Chip Formation
• These observations also indicate that the
process of chip formation is one of deformation or
plastic flow of the material, with the degree of
deformation dictating the type of chip that
will be produced.

15. Broaching
• Plastic Deformation
• Originally, it was thought that chips formed in metal
cutting were created in much the same way that wood
chips are formed when split by an axe.
• This may be partially true for brittle materials such as
cast iron, but it does not hold true for the majority of
metals.
• The process by which chips are formed with metal-
cutting tools is called plastic deformation, and was first
described by Rosenhain at the Stratsfordshire Iron and
Steel Institute in 1906.

16. Broaching
• Plastic Deformation
• What actually happens in this shearing process is that
the metal immediately ahead of the cutting edge of the
tool is severely compressed resulting in temperatures
high enough to allow plastic flow.
• When the resisting stresses in a material exceed their
elastic limit, a permanent relative motion occurs and
further deformation is withstood.

17. Broaching
• How and Where Heat is Generated
• The force or energy that is put into the tool creates
movement in a group of metal atoms in the work
piece. This group is a finite number of atoms which are
forced to change their positions in relationship to each
other.
• As the atoms in the metal ahead of the tool are
disturbed, the friction involved in their sliding over
one another is thought to be responsible for 60% or
more of the total heat generated.
• This internal friction, and the heat it generates, can be
compared to the friction and heat caused by bending a
paper clip back and forth until it breaks.

18. Broaching
• How and Where Heat is Generated
• As the tool continues to push through the work piece, a chip
eventually slides up the cutting face of the tool. This sliding
creates an external friction which again releases heat. This
external friction accounts for about 30% of the total heat
generated.
• The third area of heat generation is on the land or flank of
the tool. This area accounts for about 10% of the heat
generated.

19. Advantages & Disadvantages
• Advantages
• Rough to finish in one pass
• Production rates are high
• Cutting time is quick
• Rapid load and unload of parts
• External and internal features
• Any form that can be produced on a broaching tool
can be produced
• Production tolerances are excellent
• Surface finishes are equal to milling
• Operator skill is low

20. Advantages & Disadvantages
• Disadvantages
• Tooling cost can be high
• In some cases--not suited for low production rates
• Parts to be broached must be strong enough to
withstand the forces of the process
• Surface to be broached must be accessible

21. Methods of Operation
• Pull broaching - broach is pulled through or
across stationary work
• Push broaching - broach is pushed through or
across work
• Surface broaching - either the work or the
broach moves across the other
• Continuous broaching - the work is moved
continuously against stationary broaches. The
path of the movement may be straight or
circular.

22. Machines
• Vertical single and double slide - Table moves
part into position for broaching, part is
broached and the table retracts for unloading.
• Vertical push broaching - Used for internal features
such as holes, rounds, or slots.
• Vertical pull down
• Tool is suspended above work
• Lowered into pull mechanism in the base of the machine
• Advantages
• Part positioning is easy
• Large parts are handled efficiently

23. Machines
• Horizontal
• Versatile machine capable of producing internal and external
features
• key-ways
• gear teeth
• riffling
• High cutting speeds in the range of 10-40ft/min with
return speeds of 110 ft/min
• MRR of ¼ in per stroke is possible

24. Methods of Operation

25. Machines• Horizontal

26. Machines
• Rotary
• Parts are mounted to a rotating table and are moved to
different stations for different operations
• Primarily used on small parts
• Typical operations include:
• Slotting
• Holes
• Key-ways

27. Broaching Tools Design &
Construction
• Considerations
• Material to be broached
• Size and shape of cut
• Quality of surface finish
• Part tolerance
• Productions rates
• Type of machine
• Workholding method
• Strength of the workpiece

29. Sawing
• Depending on part tolerance, sawing can be a vital first
operation or the total process.

30. Machines Classifications
• Reciprocating saws
• Horizontal hacksaw and vertical
sawing machines
• Light to heavy duty
• Simple and most economical to
operate
• Manual to fully automatic feed
mechanisms
• Uses blades similar to hacksaw
blades

31. Machines Classifications
• Circular saws
• Sometimes called cold sawing
machines
• Saw blades are large and rotate
at low Rpms
• Cutting is similar to a milling
operation due to geometry of
saw blade

32. Machines Classifications
• Band saws
• Irregular shapes
• Very versatile
• Profile cuts
• Internal cuts
• external configurations
• Blades are continuous
• HSS - Carbide tipped
• Diamond impregnated
• Filing

33. Machines Classifications
• Band saws
1
2
3

34. Saw Blades
• Circular
• Straight
• Band

35. Saw Blades
• Terminology
• Set of the blade - Directional offset, left-right, from the
blades centerline. Sometimes referred to as the “kref.”
The kref provides clearance for the blade as it cuts
through the work.
• Straight - one tooth left one tooth right. Typically used
for brass, copper, and plastic.
• Raker - Three tooth sequence, left, right, straight.
Typically used for steel and cast iron.
• Wavy - Alternate arrangement of several teeth to the
right and left. Used to cut tubes and light sheet metal.

36. Saw Blades

37. Saw Blades
• Tooth forms
• Variable positive
• Variable
• Standard
• Skip
• Hook