1. Machine tools and their applications
Unit – I
Machine tools and their applications

2. Syllabus Drilling machine:
Types of drills and operations. Twist drill geometry, Types of drilling machine, Tool holder, Calculation of machining time for Drilling Process
Milling machine:
Types of milling machines, Cutter-types and geometry and their applications. Universal dividing head, Methods of Indexing: Simple, Compound, Differential.
Numericals based on indexing.
Calculation of machining time for Milling processes(Numericals)
Broaching:
Introduction to broaching, Broach tool geometry, Types of broaching machines and operations.Planner and Boring Machines.(Introduction and types)

3. Milling machine

4. University Questions Write short note on : i. Thread Milling
ii. Helical Slot Milling
iii. Cam Milling Operation
iv. Universal Dividing Head
v. Milling Cutter Geometry (5 mks each)
Explain with neat sketch the following Milling Operations:
i. Form Milling
ii. Plain Milling (6 mks)
Describe compound indexing with suitable example.
(6 mks)

5. University Questions
4. Explain the procedure to cut a spur gear on Milling Machine
(7 mks)
5. Write a short note on work holding devices in Milling Machine
6. With figure explain mechanism of knee type milling machine
(8 mks)
7. Differentiate :
i. Up milling and Down milling
ii. Gang milling and straddle milling (8 mks)

6. MILLING
Milling: is a metal cutting operation in which the excess material from the work piece is removed by rotating multipoint cutting tool called milling cutter.
Milling machine: is a power operated machine tool in which work piece mounted on a moving table is machined to various shapes when moved under a slow revolving serrated cutter.

7. PRINCIPLE OF MILLING The milling process:
Typically uses a multi-tooth cutter
Work is fed into the rotating cutter
Capable of high MRR
Well suited for mass production applications
Cutting tools for this process are called milling cutters

8. COMPARISON BETWEEN UP MILLING & DOWN MILLING
SL. NO.
UP MILLING
(CONVENTIONAL MILLING)
DOWN MILLING
(CLIMB MILLING) 01
Work piece fed in the opposite direction that of the cutter.
Work piece fed in the same direction that of the cutter. 02
Chips are progressively thicker.
Chips are progressively thinner. 03
Strong clamping is required since the cutting force is directed upwards & tends to lift the work piece.
Strong clamping is not required since the cutting force is directed downwards & keep the work piece pressed to the table. 04
Gives poor surface finish, since chips gets accumulated at the cutting zone.
Gives good surface finish, since the chips are thrown away during cutting. 05
Used for hard materials.
Used for soft materials and finishing operations.

9. CLASSIFICATION OF MILLING MACHINES
1. Column and knee milling machines a. Plain column & knee type milling machine - Horizontal spindle type - Vertical spindle type 2. Bed type milling machine 3. Planer type milling machine 4. Special purpose milling machine a. Tracer controlled milling machine b. Thread milling machine c. CNC milling machine

10. HORIZONTAL MILLING MACHINE
MAJOR PARTS :
BASE
COLUMN
SPINDLE
OVERARM
KNEE
SADDLE
WORKTABLE
FIG. HORIZONTAL MILLING MACHINE

12. VERTICAL MILLING MACHINE
MAJOR PARTS :
BASE
COLUMN
SPINDLE
SPINDLE HEAD
KNEE
SADDLE
WORKTABLE
FIG. VERTICAL MILLING MACHINE

14. DIFFERENCES BETWEEN HORIZONTAL & VERTICAL MILLING MACHINES
SL. NO.
HORIZONTAL MILLING MACHINE
VERTICAL MILLING MACHINE 01
Spindle is horizontal & parallel to the worktable.
Spindle is vertical & perpendicular to the worktable. 02
Cutter cannot be moved up & down.
Cutter can be moved up & down. 03
Cutter is mounted on the arbor.
Cutter is directly mounted on the spindle. 04
Spindle cannot be tilted.
Spindle can be tilted for angular cutting. 05
Operations such as plain milling, gear cutting, form milling, straddle milling, gang milling etc., can be performed.
Operations such as slot milling, T-slot milling, angular milling, flat milling etc., can be performed and also drilling, boring and reaming can be carried out.

15. MILLING OPERATIONS Plain or slab milling Face milling End milling
Slot milling
Angular milling
Form milling
Straddle milling
Gang milling
Slitting or saw milling
Gear cutting

16. PLAIN/SURFACE/ SLAB MILLING
Plain Milling:
Process to get the flat surface on the work piece in which the cutter axis and work piece axis are parallel.
Cutter: Plain/ Slab milling cutter.
Machine: Horizontal Milling m/c.
FIG. PLAIN MILLING

17. FACE MILLING Face Milling:
Operation carried out for producing a flat surface, which is perpendicular to the axis of rotating cutter.
Cutter: Face milling cutter.
Machine: Vertical Milling Machine
FIG. FACE MILLING

18. END MILLING End Milling:
Operation performed for producing flat surfaces, slots, grooves or finishing the edges of the work piece.
Cutter: End milling cutter.
Machine: Vertical Milling Machine
FIG. END MILLING

19. SLOT MILLING SLOT Milling:
Operation of producing slots like T-slots, plain slots, dovetail slots etc.,
Cutter: End milling cutter, T-slot cutter, dovetail cutter or side milling cutter
Machine: Vertical Milling Machine
FIG. T-SLOT MILLING
FIG. DOVE TAIL SLOT MILLING

20. ANGULAR MILLING Angular Milling:
Operation of producing all types of angular cuts like V-notches and grooves, serrations and angular surfaces.
Cutter: Double angle cutter.
Machine: Horizontal Milling Machine
FIG. ANGULAR MILLING

21. FORM MILLING End Milling:
Operation of producing all types of angular cuts like V-notches and grooves, serrations and angular surfaces.
Cutter: Double angle cutter.
Machine: Horizontal Milling Machine
FIG. FORM MILLING

22. STRADDLE MILLING Straddle Milling:
Operation of machining two parallel surfaces simultaneously on a work piece.
Cutter: 2 or more side & face milling cutters
Machine: Horizontal Milling Machine
FIG. STRADDLE MILLING

23. GANG MILLING Gang Milling:
Process to get different profiles on the work piece simultaneously with two or more cutters at one stretch.
Cutter: Different cutters as required.
Machine: Horizontal Milling Machine
FIG. GANG MILLING

25. SPECIFICATIONS OF MILLING MACHINE
Size of the work table: expressed in length x width Eg: 1500 x 30mm.
Longitudinal movement: Total movement of table in mm(X-direction). Eg:800mm
Transverse movement: Total movement of saddle along with table in mm(Y-direction). Eg:200mm
Vertical movement: Total movement of table, saddle & knee in mm mm(Z-direction). Eg:380mm
Range of the speed: Speed variation in the gear box in RPM. Eg: 45 to 200 rpm.
Power capacity of the motor in HP. Eg: 2 HP

26. Milling Cutters

27. More Milling Cutters

28. Formed Cutters
Concave
Convex
Gear Tooth
Metal-Slitting Saws

29. Cutting Tool Material Choices
Carbon and medium alloy steels
High Speed Steels
Cast-cobalt alloys
Carbides (or cemented or sintered carbides)
Coated tools
Alumina based ceramics
Cubic boron nitride
Diamond

30. Plain Milling Cutter Geometry
Used for peripheral or slab milling
Fig : Tool geometry elements of an 18‑tooth plain milling cutter

31. Indexing Methods
It is a division of Job periphery into a desired number of equal divisions It is followed by the controlled movement of the crank such that , the workpiece rotates through a definite angle after each cut is over

32. Methods of Indexing Direct Simple or Plain Compound Differential
Angular

33. Indexing (Dividing) Head
One of the most important attachments for milling machine
Used to divide circumference of workpiece into equally spaced divisions when milling gear teeth, squares, hexagons, and octagons
Also used to rotate workpiece at predetermined ratio to table feed rate

34. Indexing Devices
Universal Dividing Head

35. Direct Indexing Simplest form of indexing
Used for quick indexing of workpiece when cutting flutes, hexagons, squares, etc.
Plain Dividing Head

36. Direct Indexing Divisions
Direct indexing plate usually contains three sets of hole circles or slots: 24, 30, and 36
Number of divisions possible to index limited to numbers that are factors of 24, 30, 36
Slots Direct indexing divisions
_ 6 8 _ __ 12 __ __ 24 __ __
_ 5 6 _ _ 10 __ 15 __ __ 30 __
_ 6 _ 9 __ 12 __ 18 __ __ 36

37. Example: Direct Indexing
What direct indexing is necessary to mill eight flutes on a reamer blank?
Since the 24-hole circle is the only one divisible by 8 (the required number of divisions), it is the only circle that can be used in this case.
Slots Direct indexing divisions
_ 6 8 _ __ 12 __ __ 24 __ __
_ 5 6 _ _ 10 __ 15 __ __ 30 __
_ 6 _ 9 __ 12 __ 18 __ __ 36
Never count the hole or slot in which the index pin is engaged.

38. Simple Indexing
Calculating the indexing or number of turns of crank for most divisions, simply divide 40 by number of divisions to be cut or,

39. Index Plate and Sector Arms
Circular plate provided with series of equally spaced holes into which index crank pin engages
Sector arms
Fit on front of plate and may be set to any portion of a complete turn

41. Index Head Parts

42. Simple Indexing The indexing required to cut eight flutes:
The indexing required to cut seven flutes:
The five-sevenths turn involves use of an index plate and sector arms.

43. Index-plate hole circles
Brown & Sharpe
Plate
Plate
Plate
Cincinnati Standard Plate
One side
Other side

44. Brown & Sharpe dividing head : Index Plate 1

45. Compound Indexing
Two separate movements of index crank in two different hole circles of one index plate to obtain crank movement not obtainable by simple indexing
Two movements
One of index crank as in simple indexing
Second of index plate – after locking the plate with plunger

46. Compound Indexing

47. First movement –
crank pin is rotated through required number of spaces in one of the hole circles of index plate and crank pin is engaged
Second movement –
Removing rear lock pin and rotating plate together with index crank – forward or backward through calculated number of spaces of another hole circle and then lock pin is engaged

48. Rule for compound indexing

49. N – No of divisions required
N1 - hole circle used by crank pin
N2- hole circle used by lock pin
n1 – hole spaces moved by crank pin in N1 hole circle
n2 - hole spaces moved by lock pin in N2 hole circle

50. Numerical :
Index 69 divisions by compound indexing
= 𝑋 𝑎 ± 𝑋 𝑏
Assumption :
Index plates of 23 and 27 hole circles are selected

51. Solution
Step 1: factorize the no of required divisions ( A ) 69= 3 x 23 Step 2: factorize the standard number 40 ( B ) 40 = 10 x 4 Step 3: factorize the difference of selected hole circles i.e. 23 and 27 ( C ) Difference = 27 – 23 = 4 therefore , 4 = 2 x 2

52. Solution
Step 4: factorize the no of holes of one circle and the other ( D ) 23 = 23 and 27 = 3 x 9 Step 5: substitute in the relation : 𝐴 ∗ 𝐶 𝐵 ∗ 𝐷 = 3 𝑥 23 𝑥 4 10 𝑥 4 𝑥 23 𝑥 ( 9 𝑥 3 ) = 1 90 The required indexing movements are obtained by , = 𝑋 𝑎 - 𝑋 𝑏 = − =

53. Solution It means crank is moved 21 holes on 23 holes circle and
the plate and crank 9 holes on 27 hole circle in the opposite direction
Applying second check,
Crank movement = =
So obtained movements are correct

54. Differential indexing
Required division is obtained by combination of two movements
Movement of index similar to simple indexing
2. Simultaneous movement of index plate when
crank is turned

55. Differential indexing set up
using Simple Gear Train
A Gear train is used (simple or compound), which connects dividing head spindle to worm spindle, to move index plate

56. Differential indexing set up
using compound Gear Train

57. Movement of index plate may be added or subtracted according to direction of rotation of plate
Change gears –
24, 28 , 32 , 40, 44, 48 , 56 ,64 , 72 , 86 ,100

58. Rule for differential indexing
Gear ratio, indexing movement of crank and number of idlers
Gear ratio
N = required number of divisions to be indexed
A = selected number which can be indexed by plain
indexing and number is approximately equal to N
In gear ratio so calculated, numerators of fraction indicates driving gears on index head spindle and denominator indicates driven gears on index plate

59. Index crank movement = 40 𝐴
Index crank will have to be moved by an amount (40/A) for N number of complete division of work
Index crank should move in same direction or opposite to each other depending on type of gearing ratio and selected number A chosen
If (A-N) is positive plate must rotate in same direction as crank and if (A-N) is negative the index plate must rotate in direction opposite to that of a crank

60. To achieve these conditions number of idlers used depends upon :
a. If gear train is simple and ( A-N) is positive , only one idle gear is used
b. If gear train is compound and (A-N) is positive, no idle gear is used
c. If gear train is simple and (A-N) is negative, two idler are used
d. If gear train is compound and (A-N) is negative , only one idle is used.

61. Index 83 divisions
First find out whether index crank can be indexed by plain indexing or not
Index crank movement in plain indexing
= 40/N = 40/83
since there is no plate with 83 number of holes number can not be indexed by plain indexing

62. Assume A - let us take A = 86
( 86 is near to 83 and can be indexed by plain indexing)

63. Gear ratio

64. Therefore, driver gears = 72,40
driven gears = 24,86
Index crank movement
For complete indexing , index crank will be have to be moved by 20 holes in 43 circle hole
As ( A- N) i.e. (86-83) = 3 , is positive and gearing ratio is compound , no idler is required