Drilling and boring

drilling and boring machines

1. Unit-III(B ) Drilling and Boring Machines By D. Kanaka Raja Department of mechanical engineering, AITS

2. Drilling is the operation of producing circular hole in the work-piece by using a rotating cutter called DRILL. The machine used for drilling is called drilling machine. The drilling operation can also be accomplished in lathe, in which the drill is held in tailstock and the work is held by the chuck. The most common drill used is the twist drill. It is the simplest and accurate machine used in production shop. Drilling

3. Drilling machine Drilling machine Spindle Turns drill to advance into work (hand or automatically) Work table Holds workpiece rigidly in place as hole drilled Used primarily to produce holes in metal Other operations: tapping, reaming, boring, counter boring, countersinking, spot-facing

4. Working principal of drilling machine The rotating edge of the drill exerts a large force on the workpiece and the hole is generated. The removal of metal in a drilling operation is by shearing and extrusion.

5. Specifications of drilling machine Size of drilling table. Largest bit the machine can held. Maximum size of the hole that can be drilled. Maximum size the work piece that can be held. Power of the motor, spindle speed or feed.

6. Tool Nomenclature

7. Tool Nomenclature

8. Tool Nomenclature

9. Tool Nomenclature

10. Tool Nomenclature

11. Types of drilling machines a) Based on construction: Portable, Sensitive or bench drilling machine Radial, up-right, Gang, Multi-spindle Automatic Turret Deep hole b)Based on Feed: Hand and Power driven Portable drilling machine

12. Portable drilling machine It is a small light weight, compact and self contained unit that can drill holes upto 12.5 mm diameter. The machine is driven by a small electric motor operating at high speed. The machine is capable of drilling holes in the workpieces in any position.

13. Sensitive or Bench Drilling Machine These are light duty vehicles. Mounted on benches. To drill small diameter holes ,a twist drill is fitted in the drill chuck. This design is used to drill hole from 1.5mm to 15mm diameter. The controls are light and delicate speeds from 800 to 900 rpm are typical range.

14. Sensitive Drilling Machine

15. Drive Mechanism in Sensitive DM

16. Up-Right Drilling Machine Similar to sensitive drills have power feed mechanism for rotating drills and are designed for heavier. It is used for heavier work. Drill holes upto 50mm Table can move vertically and radially

17. Up-Right Drilling Machine

18. Radial Drilling Machine It the largest and most versatile used fro drilling medium to large and heavy work pieces. It can be radially adjusted around the column in any position over the work to get different size and shapes of work. The moments may be either manual or power driven. The table is to be rotated through 360 deg. The wide rang of power are as well as sensitive and geared manual feeds.

19. Radial drilling machine This machine is used for drilling medium to large heavy work pieces. Types of radial drilling machine. 1) plain radial drilling machine 2) semi universal drilling machine 3) universal drilling machine

20. Radial Drilling Machine

21. Drive in RDM

22. Gang drilling machine When drilling spindles are mounted on a single table, it is known as a gang drill. Each of these spindles can be independently set for different speed and depth of cut. Such machines are useful when number of holes of different sizes are to be drilled on the same work piece. Apart from drilling, a number of other machining operations like reaming counter boring, tapping etc can also be performed at a time on this machine.

23. Gang Drilling Machine

24. Turret Type Drilling Machine The stations are set up with a variety of tools numerical control is a also available. Two fixtures can be located side by on the workable table, thus permitting loading and unloading of one part while the other part is being machined this reduces the machine cycle.

25. Turret Type Drilling Machine

26. Deep hole drilling These machines are used for drilling holes whose depth exceed normal drill size. These machines are operated at high speed and low feed. These machines are either horizontal or vertical. The work or the drill may revolve. most machines are of horizontal construction using a center cut gun drill, which has a single cutting edge with a straight flute running througout its length. These machines are very useful for drilling deep holes in rifle travels, crankshafts.

27. Deep hole DM

28. Deep hole drilling machine Very deep holes of L/D ratio 6 to even 30, required for rifle barrels, long spindles, oil holes in shafts, bearings, connecting rods etc, are very difficult to make for slenderness of the drills and difficulties in cutting fluid application and chip removal. Such drilling cannot be done in ordinary drilling machines and bordinary drills. It needs machines like deep hole drilling machine such as gun drilling machines with horizontal axis which are provided with

29. Drilling operations… Operations that can be performed in a drilling machine are Drilling Reaming Boring Counter boring Countersinking Tapping and Spot Facing

30. Drilling operations…

31. Operations Performed Drilling Operation of producing hole by removing metal from solid mass using twist drill Countersinking Operation of producing tapered or cone-shaped enlargement to end of hole

32. Operations Performed Reaming Operation of sizing and producing smooth, round hole from previously drilled or bored hole Boring Truing and enlarging hole by means of single-point cutting tool

33. Operations Performed Tapping Cutting internal threads in hole with cutting tool called tap Counterboring Enlarging top of previously drilled hole to given depth to provide square shoulder for head of bolt or capscrew

34. Operations in drilling machine

35. Counter bore and spot facing

36. Operations in drilling machine

37. Tool Holding devices Tool-holding devices are Used to hold or drive cutting tool The different methods used for holding drill in a drill spindle are By directly fitting in the spindle hole. By using drill sleeve By using drill socket By using drill chuck

38. Tool-Holding Devices Drill press spindle provides means of holding and driving cutting tool End may be tapered or threaded for mounting drill chuck Most common Drill chucks Drill sleeves Drill sockets

39. Drill fixed to the spindle Drilling operations Drilling Centre Hole Drilling Deep Holes Drilling Thin Material Drilling Pilot Hole

40. Drill Chucks Most common devices used for holding straight-shank cutting tools Most contain three jaws that move simultaneously when outer sleeve turned Hold straight shank of cutting tool securely Two common types Key Keyless

41. Work Holding Devices

42. Work Holding Devices

43. Work Holding Devices

44. Chucks Hold straight-shank drills Mounted on drill press spindle Taper Threads Held in spindle by self-holding taper in larger machines Four types of drill chucks

45. Types of Drill Chucks Key-type Most common Three jaws move simultaneously when outer sleeve turned Tighten with key Keyless Chuck loosened or tightened by hand without key Precision keyless Holds smaller drills accurately

46. Drill Chucks

47. Tool Holder

48. Drill Types

49. Drill Types

50. Types of cutters Reamers :- Multi tooth cutting tool Accurate way of sizing and finishing the pre-existing hole. Accuracy of 0.005mm can be achieved Boring Tool:- Single point cutting tool. Boring tool is held in the boring bar which has the shank. Accuracy of 0.005mm can be achieved.

51. Types of cutters Countersinks :- Special angled cone shaped enlargement at the end of the hole Cutting edges at the end of conical surface. Cone angles of 60 ° , 82 ° , 90 ° , 100 ° , 110 ° , 120 ° Counter Bore Tool:- Special cutters uses a pilot to guide the cutting action . Accommodates the heads of bolts.

52. Types of cutters Combined Countersinks and central drill :- Special drilling tool to start the hole accurately. At the end it makes countersinks in the work piece. Gun drill :- Machining of lengthy holes with less feed rates. To overcome the heating and short life of the normal drill tool

53. Types of cutters Tapping:- For cutting internal thread Multi cutting edge tool. Tapping is performed either by hand or by machine. Minor dia of the thread is drilled and then tapping is done.

54. Work Holding Devices

55. Work Holding Devices 1. Machine Table Vice

56. Step Blocks Clamps V-Blocks Angles Jigs T- Slots Bolt Work Holding Devices

57. Drill Materials The two most common types are 1. HSS drill - Low cost 2. Carbide- tipped drills - high production and in CNC machines Other types are Solid Carbide drill, TiN coated drills, carbide coated masonry drills, parabolic drills, split point drill

58. Grinding of Drills

59. Grinding of Drills

60. Parameters Definitions Cutting Speed (v):- It’s the peripheral speed of the drill v = *D*N where D = dia of the drill in m N = Speed of rotation in rpm Feed Rate (f):- It’s the movement of drill along the axis (rpm) Depth of Cut (d):- The distance from the machined surface to the drill axis d = D / 2

61. Material Removal Rate:- It’s the volume of material removed by the drill per unit time MRR = ( D 2 / 4) * f * N mm 3 / min Machining Time (T) :- It depends upon the length (l) of the hole to be drilled , to the Speed (N) and feed (f) of the drill t = L / f N min

62. Reaming

63. 86 What is meant by boring? Boring is the process of enlarging an existing drilled holes with a single point cutting tool. Boring operation can be performed on engine lathe Fig.1

64. Classification of boring machine Horizontal boring machine ( production machines) Table type HBM Planer type HBM Floor type HBM Vertical boring machine( production machines) Jig boring machine

65. Horizontal boring machine

66. Horizontal boring machine

67. Horizontal boring machine The table type or universal type is the most versatile and commonly used horizontal boring machine. Bed a heavy and strong bed carries the entire load of different parts, work piece and tool over it. Columns a two vertical columns, one on each end of the table. Head stock the head stock can be moved vertically along the main column. Load bearing end support it supports the end of a long boring bar and can be adjusted vertically along the end support column. Horizontal table it is mounted on a saddle and can be moved horizontal forward and backward and side by moving the saddle.

68. Horizontal boring machine

69. Vertical boring machine

70. Vertical boring machine

71. Vertical boring machine The parts whose length or height is than diameter are machined. The work is fastened on a horizontal revolving table and the cutting tool or tools which are stationary , advance vertically into it as the revolves. Horizontal cross rail is carried on vertical sideways and carries the tool holder slide or slides. Most machine also have a slide tool head. Vertical boring machine is sometimes called a rotary planer and its cutting action on flat disc is identical with a planer. These machines rated according to their table diameter, vary in size from 0.9 to 12m.

72. Floor type boring machine

73. Planer type bm

74. Multiple head bm

75. Turret type bm

76. Jig Boring Machine Jig boring machine resembles in appearance to a vertical milling machine. Rugged enough for heavy cuts and sensitive enough for light cuts . Essential for modern mass production The machining accuracy of jig boring machine is very high, within a range of 0.0025 mm.

77. 101 Need of Jig Boring Machine Jig boring machines are mainly to perform machining operations like Boring. Drilling. Reaming. Counter boring holes in metal jigs Counter-sinking holes in metal work pieces. Some jig boring machines are used for accurately enlarging the Existing holes. Making their diameters highly accurate Boring can correct hole location, size, or alignment and can produce a good finish if a fine feed and correct tool are used.

78. 102 Need of Jig Boring Machine Jig boring can also maintain high accuracy between multiple holes or holes and surfaces. Some jig boring machines are designed to machine holes with the tightest tolerances possible with a machine tool. The constant demand for accuracy within many branches of metalworking has been fulfilled with the help of applications possible by jig-boring machines.

79. Jig Boring Machine Jig boring machines are used in precision tool room applications for locating and boring holes in Jigs. Fixtures. Gauges. And other precision parts. To prevent the influence of ambient temperature on machining accuracy Jig boring machines should be installed in a special environmental enclosures (i.e., in a temperature controlled rooms) with temperature maintained at a level of 20 °C. Jig borers can be used as coordinate measuring machine for inspection and precision layout operation . 103

80. Simple Jig Boring Machine column spindle head quill boring tool spindle table bed saddle Line Diagram Fig.2 PARTS OF JIG BORING MACHINE

81. Jig Boring Machine 105 Fig.3

82. Jig boring machine The main distinguishing features of these machines are : The spindle and other parts are rigid to prevent deflection. The spindle runs in preloaded ant frictional bearings. The spindle housing is made of material having very low co-efficient of linear expansion . For boring, the work pieces are clamped on the table by T-bolts and straps. an existing hole is enlarged by using a single point tool. The single point tool produces Better surface finish. And locates holes with maximum accuracy. 106

83. Jig boring machine ⎯ high spindle speed ⎯ high rigidity ⎯ tool guide ⎯ Pressurized cutting oil for effective cooling, chip removal and lubrication at the drill tip. Deep hole drilling machines are available with both hard automation and CNC system.

84. Jig boring machine The principle of boring using single point tool is illustrated in fig. 108 Fig.4

85. Parts of jig boring machine

86. Cutting forces

87. Kinematic System of general purpose drilling machine and their principle of working

88. Kinematic System of general purpose drilling machine and their principle of working Mechanisms to enable transform and transmit motion(s) from the power source(s) to the cutting tool and the workpiece for the desired machining action. a typical kinematic system of a very general purpose drilling machine, i.e., a column drilling machine having 12 spindle speeds and 6 feeds. The kinematic system enables the drilling machine the following essential works;

89. Kinematic System of general purpose drilling machine and their principle of working Cutting motion: The cutting motion in drilling machines is attained by rotating the drill at different speeds ( r.p.m .). Like centre lathes, milling machines etc, drilling machines also need to have a reasonably large number of spindle speeds to cover the useful ranges of work material, tool material, drill diameter, machining and machine tool conditions. The drill gets its rotary motion from the motor through the speed gear box (SGB) and a pair of bevel gears. For the same motor speed, the drill speed can be changed to any of the 12 speeds by shifting the cluster gears in the SGB. The direction of rotation of the drill can be changed, if needed, by operating the clutch in the speed reversal mechanism, RM-s shown in the figure.

90. Kinematic System of general purpose drilling machine and their principle of working Feed motion In drilling machines, generally both the cutting motion and feed motion are imparted to the drill. Like cutting velocity or speed, the feed (rate) also needs varying (within a range) depending upon the tool-work materials and other conditions and requirements. drill receives its feed motion from the output shaft of the SGB through the feed gear box (FGA), and the clutch. The feed rate can be changed to any of the 6 rates by shifting the gears in the FGB. And the automatic feed direction can be reversed, when required, by operating the speed reversal mechanism, RM-s as shown

91. Tool work mounting The taper shank drills are fitted into the taper hole of the spindle either directly or through taper socket(s). Small straight shank drills are fitted through a drill chuck having taper shank. The work piece is kept rigidly fixed on the bed (of the table). Small jobs are generally held in vice and large or odd shaped jobs are directly mounted on the bed by clamping tools using the T-slots made in the top and side surfaces of the bed as indicated Kinematic System of general purpose drilling machine and their principle of working