1. Hand-Type Cutting Tools

2. Objectives
Select and use the proper hacksaw blade for sawing a variety of materials
Select and use a variety of files to perform various filing operations
Identify and know the purpose of rotary files, ground burrs, and scrapers

3. Sawing, Filing and Scraping
Often necessary to perform certain metal-cutting operations at bench or on job
Common tools
Hacksaws
Files
Scrapers
Usually need practice to become proficient

4. Pistol-Grip Hand Hacksaw
Composed of three main parts
Frame, handle, and blade
Solid frame more rigid and will accommodate blades of one specific length
Adjustable frame more common and will take blades from 10 to 12 in. long
Wing nut provides adjustment

5. Hacksaw Blades
Made of high-speed molybdenum or tungsten-alloy steel (hardened and tempered)
Two types
Solid blade (all-hard)
Hardened throughout and very brittle
Flexible blade
Teeth hardened, while back of blade soft and flexible
Stand more abuse than all-hard blade, but will not last long in general use
Used on channel iron, tubing, copper and aluminum

6. Blade Pitch Number of teeth per inch Manufactured in various pitches
14, 18, 24, and 32
General use choice – 18 in. tooth blade
Choose as coarse blade as possible
Provides plenty of chip clearance and to cut through work as quickly as possible
Should have at least two teeth in contact with work at all times
Prevent work from jamming and stripping teeth

7. Guide for Proper Blade Selection
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8. Guide for Proper Blade Selection
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

9. Guide for Proper Blade Selection
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10. Guide for Proper Blade Selection
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. Files Hand cutting tool made of high-carbon steel
Series of teeth cut on body by parallel chisel cuts
Used to remove surplus metal and to produce finished surfaces
Manufactured in variety of types and shapes
Each has specific purpose
Two classes: single-cut and double-cut

12. Single-cut Files
Single row of parallel teeth running diagonally across face
Used when smooth finish desired
Include mill, long-angle lathe, and saw files
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13. Double-cut Files Two intersecting rows of teeth
First row coarser and called overcut
Second row called upcut
Hundreds of cutting teeth
Provide for fast removal of metals and easy clearing of chips
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14. Degrees of Coarseness
Both single- and double-cut files come in various degrees of coarseness
Rough
Coarse
Bastard
Second-cut
Smooth
Dead smooth
Most Common
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15. Machinist Files Types most commonly used by machinists Flat Pillar
Hand
Round
Half-round
Square
Pillar
Three-quarter
Warding
Knife

16. Cross-sectional Views of Machinists' Files
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17. Care of Files Do not store files where they rub together
Never use file as pry of hammer
Do not knock file on vise or other metallic object to clean it (use brush or file card)
Apply pressure only on forward stroke
Do not press too hard on new file
Too much pressure also results in "pinning" which scratches work surface
Small particles wedged between teeth

18. Points to be Observed When Cross-filing
Never use file without handle
Fasten work to be filed in vise, at about elbow height
To produce flat surface, hold right hand, right forearm and left hand in horizontal plane
Push file across work face in straight line
Do not rock file

19. Apply pressure only on forward stroke
Never rub fingers or hand across surface being filed
Oil will clog file
Oil causes file to slide over instead of cutting
Keep file clean by using file card frequently
For rough filing, use double-cut file and cross stroke at regular intervals to keep surface flat and straight. When finishing, use single-cut file and take shorter strokes to keep file flat.

20. Draw Filing and Polishing
Used to produce smooth, flat surface on workpiece
Removes file marks and scratches left by cross-filing
Polishing
After surface filed, finished with abrasive cloth to remove small scratches left by file
Moved back and forth along work

21. Copyright © The McGraw-Hill Companies, Inc
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22. Rotary Files Teeth cut and form broken lines
Dissipate heat of friction
Useful for work on tough die steels, forgings, and scaly surfaces
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23. Ground Burrs May be made of high-speed steel or carbide
Teeth uniform in tooth shape and size
Unbroken flutes
Flutes machine ground to master burr to ensure uniformity of tooth shape and size
May be made of high-speed steel or carbide
Carbide last up to 100 times longer
Used on nonferrous metals
Better chip clearance
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24. Grinding
Section 15

25. Grinding Characteristics of an abrasive must be:
Harder than material being ground
Strong enough to withstand grinding pressures
Heat-resistant so that it does not become dull at grinding temperatures
Friable (capable of fracturing) so when cutting edges become dull, they will break off and present new sharp surfaces to material being ground

26. Types of Abrasives
Unit 80

27. Objectives
Describe the manufacture of aluminum oxide and silicon carbide abrasives
Select the proper grinding wheel for each type of work material
Discuss the applications of grinding wheels and abrasive products

28. Abrasive Classes Natural abrasives Manufactured abrasives
Sandstone, garnet, flint, emery, quartz, corundum
Used prior to early part of 20th century
Almost totally replaced by manufactured abrasives
Best natural abrasives is diamond (high cost)
Manufactured abrasives
Used because grain size, shape and purity can be closely controlled
Aluminum oxide, silicon, carbide, boron carbide, cubic boron nitride and manufactured diamond

29. Aluminum Oxide Most important abrasive Make up 75% of grinding wheels
Used for high-tensile-strength materials
Manufactured with various degrees of purity
Hardness and brittleness increase as purity increases

30. Aluminum Oxide Purities
Regular aluminum oxide (Al2O3) at 94.5%
Tough abrasive capable of withstanding abuse
Grayish in color
Used for grinding steel, tough bronzes, etc.
Aluminum oxide at 97.5%
Not as tough as regular but still gray in color
Used in manufacture of grinding wheels for centerless, cylindrical, and internal grinding of steel and cast iron
Purest form of aluminum oxide
White material that produces sharp cutting edge
Used for grinding hardest steels and stellite

31. Silicon Carbide
Suited for grinding materials that have low tensile strength and high density
Harder and tougher than aluminum oxide
Color varies from green to black
Green used mainly for grinding cemented carbides and other hard materials
Black used for grinding cast iron and soft nonferrous metals (also ceramics)

32. Manufactured Diamonds
1954, General Electric Company produced Man-Madey diamonds in laboratory
1957, General Electric Company began commercial production of diamonds
First success involved carbon and iron sulfide in granite tube closed with tantalum disks were subjected to pressure of 66,536,750 psi and temperatures between 2550ºF
Temperatures must be high enough to melt metal saturated with carbon and start diamond growth
Industrial diamonds referred to as bort

33. Diamond Types Type RVG Diamond
Elongated, friable crystal with rough edges
Letters indicate it can be used with resinoid or vitrified bond and used for grinding ultrahard materials
Tungsten carbide
Silicon carbide
Space-age alloys
Used for wet or dry grinding

34. Type MBG-II Diamond Type MBS Diamond Tough and block-shaped crystal
Not as friable as RVG type
Used in metal-bonded grinding wheels
Used for grinding cemented carbides, sapphires, and ceramics as well as electrolytic grinding
Type MBS Diamond
Blocky, extremely tough crystal with smooth, regular surface and not friable
Used in metal-bonded saws to cut concrete, marble, tile, granite, stone, and masonry

35. Ceramic Aluminum Oxide
Known as SG abrasive, introduced by Norton Company in 1988
Outperforms conventional aluminum oxide
Made by nonfused process
Thousands of submicron-sized particles are sintered to provide single abrasive grain of uniform shape and size with more cutting edges that remain sharp
SG abrasive well suited to CNC grinding
Fewer wheel changes, less wheel dressing, higher productivity and therefore lower labor costs

36. Advantages of SG Abrasives Over Conventional Abrasives
Last 5 to 10 times longer than conventional wheels
Metal-removal rates are doubled
Heat damage to surface of very thin workpieces reduced
Grinding cycle time reduced
Dressing time reduced as much as 80%

37. Abrasive Grain
Aluminum oxide or silicon carbide abrasive used in most grinding wheels
Each grain on working surface of grinding wheel acts as separate cutting tool
Removes small metal chip as passes over surface of work
As grain becomes dull, fractures and presents new sharp cutting edge to material
Fracturing action reduces heat of friction, producing relatively cool cutting action

38. Grain Size
Abrasive ingot (pig) removed from electric furnace, crushed, grains cleaned and then sized by passing them through screens
Contain certain number of meshes or openings per inch
8-grain
24-grain
60-grain
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39. Grain Sizes General applications for various grain sizes
8 to 54 for rough grinding operations
54 to 400 for precision grinding processes
320 to 2000 for ultra precision processes to produce 2 to 4 µ (micron) finish or fine

40. Factors Affecting Selection of Grain Sizes
Type of finish desire
Type of material being ground
Amount of material to be removed
Area of contact between wheel and workpiece

41. Bond Types
Function of bond is to hold abrasive grains together in form of wheel
Six common bond types used in grinding wheel manufacture:
Vitrified
Resinoid
Rubber
Shellac
Silicate
Metal

42. Vitrified Bond Used on most grinding wheels Made of clay or feldspar
Fuses at high temperature and when cooled forms glassy bond around each grain
Strong but break down readily on wheel surface to expose new grains during grinding
Bond suited for rapid removal of metal
Not affected by water, oil, or acid

43. Resinoid Bond Synthetic resins used as bonding agents
Generally operate at 9500 sf/min
Wheels are cool-cutting and remove stock rapidly
Used for cutting-off operations, snagging, and rough grinding, as well as for roll grinding

44. Precautions to Observe When Handling and Storing Grinding Wheels
Never handle wheels carelessly
Treat them as precision instruments
Dry at a reasonable temperature
Store wheels properly
Straight or tapered wheels best stored on edge in individual racks to prevent rolling
Thin, organic bonded wheels laid on flat horizontal surface to prevent warping
Small cup and internal wheels put separately into boxes, bins, or drawers
Large cup and cylindrical wheels should be stored on flat sides with packing between wheels

45. Characteristics That Indicate Wheel Too Soft
Breaks down too fast
Poor surface finish
Cuts freely
Sparks out quickly
Difficult to maintain size
Scratches (fishtails)

46. Characteristics That Indicate Wheel Too Hard
Wheel glazes quickly
Loading (material ground fills voids)
Burned work surface
Squealing noise
Doesn't cut freely
Inaccurate work dimensions
Surface finish get progressively better
Won't spark out
Heat checks

47. Inspection of Wheels Inspect wheels after they have been received
Damage might occur during transit
Suspend and tap lightly with screwdriver handle for small wheels or with wooden mallet for larger wheels
Vitrified or silicate wheels give clear, metallic ring when sound
Organic-bonded wheels give duller ring
Cracked wheels do not produce ring

48. Surface Grinders and Accessories
Unit 81

49. Objectives
Name four methods of surface grinding and state the advantage of each
True and dress a grinding wheel
Select the proper grinding wheel to be used for each type of work material

50. Grinding Process
Workpiece brought into contact with revolving grinding wheel
Each small abrasive grain on periphery of wheel acts as individual cutting tool and removes chip of metal
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51. General Rules for Grinding
Use silicon carbide wheel for low-tensile-strength material and aluminum oxide wheel for high-tensile-strength materials
Use hard wheel on soft materials and soft wheel on hard materials
If wheel too hard, increase speed of work or decrease speed of wheel to make it act as softer wheel

52. Glazed wheel will affect finish, accuracy, and metal-removal rate.
If wheel appears too soft or wears rapidly, decrease speed of work or increase speed of wheel
Glazed wheel will affect finish, accuracy, and metal-removal rate.
Main causes of wheel glazing are:
Wheel speed too fast
Work speed too slow
Wheel too hard
Grain too small
Structure too dense

53. Surface Grinding
Refers to production of flat, contoured, and irregular surfaces on piece of work
Passed against revolving grinding wheel
Four distinct types of surface grinding machines
Horizontal spindle grinder, reciprocating table
Horizontal spindle grinder, rotary table
Vertical spindle grinder, reciprocating table
Vertical spindle grinder, rotary table

54. Guidelines for Grinding Wheel Care
When not in use, store properly
Should be tested for cracks prior to use
Select proper type wheel for job
Should be properly mounted and operated at recommended speed

55. Grinder Safety Use the right wheel Ring test the wheel before mounting
Always use mounting blotters
Tighten clamping nuts only enough to prevent wheel from slipping
Be sure flanges are flat and free from burrs and gouges

56. Check arbor holes – wheel should slip freely, not loosely, onto spindle arbor
Do not exceed maximum speed
Always use wheel guard supplied
Stand to one side whenever wheel started
Always wear safety glasses when grinding

57. Truing a Grinding Wheel
Process of making grinding wheel round and concentric with its spindle axis and producing required form of shape on wheel
Involves grinding of a portion of the abrasive section of grinding wheel

58. Dressing a Grinding Wheel
Operation of removing dull grains and metal particles
Exposes sharp cutting edges so cuts better
Reasons for dressing wheel
Reduce heat generated between work and wheel
Reduce strain on grinding wheel and machine
Improve surface finish and accuracy of work
Increase rate of metal removal

59. Procedure To True and Dress a Grinding Wheel
Check diamond for wear and if necessary, turn it in holder to expose sharp cutting edge
Clean magnetic chuck thoroughly with cloth
Place piece of paper on left-hand end of magnetic chuck
Place diamond holder on paper and energize chuck

60. Raise wheel above height of diamond
Move table longitudinally so diamond is offset approximately ½ in. to left of centerline of wheel
Adjust table laterally so diamond is positioned under high point on face of wheel
Start wheel revolving and carefully lower wheel until high point touches diamond

61. Lower grinding wheel about .001 to .002 in. per pass
Move table laterally, using crossfeed handwheel to feed diamond across face of wheel
Lower grinding wheel about .001 to .002 in. per pass
Rough-dress face of wheel until flat and dressed all around circumference
Lower wheel in. and take several passes across face of wheel

62. Helpful Ideas When Truing or Dressing Grinding Wheels
To minimize wear on diamond, rough-dress with abrasive stick
If coolant to be used during grinding, use coolant when dressing wheel
Loaded wheel indicated by discoloration of periphery or face – remove completely
If rapid removal of metal more important than surface finish, do NOT finish-dress

63. Work-Holding Devices
Work must be held in vise, held on V-blocks or bolted directly to table for some surface-grinding operations
Most of ferrous work ground on surface grinder held on magnetic chuck
Clamped to table of grinder

64. Two Types Magnetic Chucks
Electromagnetic chuck
Uses electromagnets to provide holding power
Advantages
Holding power may be varied to suit area of contact
Special switch neutralizes residual magnetism in chuck
Permanent magnetic chuck
Holding power provide by means of permanent magnets

65. Four Purposes of Grinding Fluids
Reduction of grinding heat
Lubrication
Removal of swarf from cutting area
Small metal chips and abrasive grains
Control of grinding dust

66. Types of Grinding Fluids
Soluble oil and water
Milky solution applied by flooding surface
Soluble chemical grinding fluids and water
Used with "through-the-wheel" systems
Contains rust inhibitors and bactericides
Straight oil grinding fluids
Applied by flood system and used for high finish, accuracy and long wheel life

67. Methods of Applying Coolants
Flood system
Coolant directed onto work by nozzle and recirculated through system
Through-the-wheel cooling
Fluid pumped and discharged into dovetailed groove in wheel flange (with holes), fluid forced through wheel by centrifugal force
Mist cooling system
Atomizer principle: air passes through line, as passes reservoir draws coolant and discharges it in vapor form directed at point of contact

68. Factors Affecting Surface Finish
Material being ground
Amount of material being removed
Grinding wheel selection
Grinding wheel dressing
Condition of machine
Feed

69. Surface Grinding Operations
Unit 82

70. Objectives Set up various workpieces for grinding
Observe the safety rules to operate the grinder
Grind flat, vertical, and angular surfaces

71. Surface Grinding
Primarily for grinding flat surfaces on hardened or unhardened workpiece
Perform operations such as form, angular, and vertical grinding
Good results depend on several factors:
Proper mounting
Proper wheel selection for job

72. Mounting Workpiece for Grinding Flat Work or Plates
Remove all burrs from surface of work
Clean chuck surface with clean cloth
Place piece of paper slightly larger than workpiece in center of magnetic chuck face
Place work on top of paper, and be sure to straddle as many magnetic inserts as possible
If workpiece warped, shim work to prevent rocking
Turn handle to on position
Check work to see it is held securely

73. Short Workpieces
Work that does not straddle three magnetic poles generally not held firmly enough for grinding
Advisable to straddle as many poles as possible
Set parallels or steel pieces around work to prevent it from moving
Parallels should be slightly thinner than workpiece

74. Grinder Safety
Before mounting a grinding wheel, ring test wheel to check for defects
Be sure grinding wheel properly mounted on spindle
See wheel guard covers at least one-half wheel
Make sure magnetic chuck has been turned on by trying to remove work

75. See that grinding wheel clears work before starting grinder
Be sure grinder operating at correct speed for wheel being used
When starting grinder, always stand to one side of wheel
Never attempt to clean magnetic chuck or mount and remove work until wheel has stopped completely
Always wear safety glasses when grinding

76. Procedure to Grind a Flat (Horizontal) Surface
Remove all burrs and dirt from workpiece and face of magnetic chuck
Mount work on chuck, placing piece of paper between chuck and workpiece
Check to see that work held firmly
Set table reverse dogs so center of grinding wheel clears each end of work by 1 in.

77. Set crossfeed for type of grinding operation – roughing cuts,. 030 to
Set crossfeed for type of grinding operation – roughing cuts, .030 to .050 in.; finishing cuts, .005 to .020 in.
Bring work under grinding wheel by hand, having about 18 in. of wheel edge over work
Start grinder and lower wheelhead until wheel just sparks work
Wheel may have been set on low spot of work.

78. Cutting fluid should be used whenever possible to aid grinding action keep cool
Start table traveling automatically and feed entire width of work under wheel to check for high spots
Lower wheel for every cut until surface is completed – roughing cuts, .001 to .003 in.; finishing cuts, to .001 in.
Release magnet and remove workpiece by raising one edge to break attraction

79. To Grind the Edges of a Workpiece
Edges ground square and parallel so edges may be used for further layout or operations
Flat surfaces ground first, permits them to be used as reference surfaces for setups
Clamp work to angle plate so two adjacent sides ground square without moving workpiece

80. Place ground edge of workpiece on paper
If work 1 in. thick and long enough to span three magnetic poles on chuck, and no more than 2 in. high, no angle plate required
If work less than 1 in. thick and does not span three magnetic poles, fastened to angle plate
Place ground edge on paper and place angle plate no higher than workpiece against workpiece
Turn on chuck and clamp work to angle plate
Grind third edge to required size
Repeat operations 1 to 3 and grind 4th edge

81. Mounting the Workpiece
Remove burrs from magnetic chuck and workpiece and thoroughly clean chuck
Place piece of smooth paper between work and magnetic chuck; energize chuck
Setting Speeds and Feeds
Adjust table reverse dogs so center of grinding wheel clears each end of work to be ground by 1 in.

82. Set table speed rate from 50 to 100 ft/min
Set table crossfeed:
Rough grinding – ¼ to ½ wheel width
Finish grinding – smaller crossfeed increments
Set table speed rate from 50 to 100 ft/min
Set spindle speed for size and type of CBN wheel used
Setting wheel to work surface
Set wheel to top of work surface
Traverse workpiece under revolving wheel to locate high spot of work surface

83. Move table so wheel clears edge of work surface to be ground
Coolant
Use proper grinding fluids to suit wheel and workpiece
Stop grinder spindle and adjust coolant nozzle so it is about ¼ in. above work surface and as close to wheel face as possible

84. Place dummy block, slightly lower than work surface, at right-hand end so entire surface receives coolant at all times
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85. Grinding the Surface
Start grinder spindle and lower wheelhead .001 in. for first cut
Start coolant flow
Start table reciprocating and engage crossfeed to take roughing pass
Be sure edge of grinding wheel clears side of work after each pass
Take as many passes (.001 in.) as needed
Set wheelhead for in. depth for final pass to improve surface finish