CENTRAL INSTITUTE OF PLASTICS ENGINEERING & TECHNOLOGY
Question Bank
COURSE : DPMT
SEMESTER: |||
SUBJECT : MACHINE SHOP TECHNOLOGY II
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1.Explain any threeTool holding devices used in milling machine with neat sketch?
Ans.
Arbors:
The cutter have a bore at the centre are mounted and keyed on a short shaft called arbor which is connected with the milling machine spindle by a draw bolt and driving keys.
2.Collets: A milling machine collet is a form of sleeve bushing for reducing the size of the taper hole at the nose of the milling machine spindle so that an arbor/a milling cutter having a smaller shank than the spindle taper can be fitted into it.
3. Adapter: AnAdapter is a form of collet used
on milling machine having standardized spindle end. Cutters having shanks are
usually mounted on adapters and it can be connected with spindle by a draw bolt
or it can be directly bolted to it.
2.Explain any threeWork holding devices used in milling machine with neat sketch?
Ans.1.
Angel plates: An angle plate is an L shaped piece of Cast Iron or Steel that has tapped holes or slots to facilitate the clamping of the workpiece.Angle plates are used when parts need to have machining operations performed at a 90 degree angle to the axis of the table.
2. V-Blocks: V-Blocks are precision metalworking jigs typically used to hold round metal rods or pipes for performing drilling or milling operations. They consist of a rectangular steel or cast iron block with a 90-degree channel rotated 45-degrees from the sides, forming a V-shaped channel in the top. A small groove is cut in the bottom of the "V". They often come with screw clamps to hold the work.
3. Machine vice: A machine
vice is a clamping device used to hold a workpiece securely when operating
a machine tool, such as a drill press or milling machine. It
differs from metalworking and woodworking vices as it is mounted to
the table of a machine tool instead of a workbench.
3.Types of cutters used in milling machine and explain any two with neat sketch?
Ans
· Roughing end mill
· Slab mill.
· End mill cutter.
· Ball mill cutter.
· Face mill cutter.
· Wood ruff cutter.
· Thread mill cutter
· Fly cutter.
· Slide and face cutter.
·
a. Slab Mills For heavy cutting of large and flat surfaces.
b. Side and Face Cutters This type of cutters has cutting edges on the periphery and sides of the teeth for cutting shoulders and slots.
4. What is spindle speed and Feed rate?
Ans.a)Spindle speed in revolution per minute (R.P.M.) for the cutter can be calculated from the equation:-
Where,
N = R.P.M. of the cutter.
CS = Linear Cutting Speed of the material in m/min.
d = Diameter of cutter in mm.
b) Feed rate (F) is defined as the rate of travel of the workpiece in mm/min. But most tool suppliers recommend it as the movement per tooth of the cutter (f).
Thus,
F = f. u. N
Where,
F = table feed in mm/min.
f = movement per tooth of cutter in mm.
u = number of teeth of cutter.
N = R.P.M. of the cutter.
5. Define Depth of cut?
For a certain type of cutter, a typical range of cut will be recommended by the supplier. Nevertheless, it should be noted that a finer cut is usually associated with a better surface finish as well as a long tool life.
6.Draw
and explain Up and Down milling?
In this milling, the cutter rotates in a direction opposite to the table feed It is conventionally used in most milling operations because the backlash between the lead screw and the nut of the machine table can be eliminated.
b. Down Milling
In down cut milling, the cutter rotates in the same direction as the table feed.This method is also known as Climb Milling and can only be used on machines equipped with a backlash eliminator or on a CNC milling machine. This method, when properly treated, will require less power in feeding the table and give a better surface finish on the workpiece
7. Explain any three types of Milling operation?
Ans. 1.Plain Milling
Plain milling is the milling of a flat surface with the axis of the cutter parallel to the machining surface. It can be carried out either on a horizontal machine or a vertical machine.
2. Gang Milling
Gang milling is a horizontal milling
operation that utilizes three or more milling cutters grouped together for the
milling of a complex surface in one pass. Different type and size of cutters
should be selected for achieving the desire profile on the workpiece.
3. End Milling
End Milling is the milling of a flat surface with the axis of the cutter perpendicular to the machining surface.
8. Define lubrication and functions?
Ans. Lubrication is the science of reducing friction between two solid bodies in relative motion by interposing a lubricant between their rubbing surfaces. It is the most vital singular factor in plant maintenance. It keeps the plant young, contribute to better profits by improving the life of the wear components, equipment availability and reliability. Much work has been done in this direction my improving lubrication, mechanization, modification of the existing lubricating system, elimination of lubricant wastage and thus bringing down the consumption of lubricants and wear parts.
The principal functions of lubricants are:
· Reduce friction.
· Control temperature rise.
· Control wear
· Control Corrosion
· Transmit Power in case of hydraulics.
9.What is theprocedure of Maintenance of milling
machines?
1. Cleaning of guideways
2. Inspection of oil level (sight glasses)
3. Lubrication as per lubrication chart
4. Oil renewal
5. Inspection and, if necessary, refilling of coolant tank
6. Thorough cleaning of the machine
7. Inspection of slackness of bearings
8. Inspection of electrics (contactors, limit switches, cable connections)
9. Inspection of lubrication pump
10. Coolant renewal.
10. What are the various types of milling machine?
· Horizontal milling machine
· Vertical milling machine
· Universal milling machine
· Omniversal milling machine
2.Manufacturing type or fixed bed type
· Simplex milling machine
· Duplex milling machine
· Triplex milling machine
3.Planer type milling machine
4.Special Type
· Rotary table milling machine
· Drum milling machine
11.Explain Safety measure in milling?
Ans.
· Do
not make contact with the revolving cutter.
· Use
the buddy system when moving heavy attachments.
· Do
not attempt to tighten arbor nuts using machine power.
· When
installing or removing milling cutters, always hold them with a rag to prevent
cutting your hands.
· While
setting up work, install the cutter last to avoid being cut.
· Never
adjust the workpiece or work mounting devices when the machine is operating.
12. Write short note on milling cutter material?
Nice steel with higher content of carbon (carbon content of 0.7% to 1.2%, such as T10A), v higher
hardness after quenching, low cost, but poor heat resistance.
2.Alloy tool steel
Adding a small amount of Cr, W, Mn, Si and other elements in carbon tool steel to formed carbon tool steel formation (such as 9SiCr.) It may reduce heat deformation and increase heat resistance.
3.High-speed steel materials:
It is kind of alloy tool
steel containing more alloy elements like W, Cr, and V. General high-speed
steel: like W18Cr4V, widely used for the manufacture of various cutters with
more complex shapes, such as twist drills, milling cutters, broaches, gear
cutters and other forming tool, and so on.
13. What is a necessary properties of cutter material?
· Higher hardness and wear resistance
· Sufficient strength and toughness
· Better heat resistance
· Excellent technology and economy
14. Differentiate between conventional and unconventional
milling?
Ans. Conventional machining method:
Conventional machines require direct contact of tool and work piece/material. For example to cut an aluminum bar, an iron fast rotating cutter may be used. These methods involve a physical contact between the cutting tool and the material being cut or processed.
As the name suggest, unconventional machining method involves the use of modern and advanced technology for machine processing. There is no physical contact between the tool and the work piece in such process. Tools used for cutting in unconventional methods are laser beams, electric beam, electric arc, infrared beam, Plasma cutting and so on depending on the type of working material.
15. Draw Woodruff keyway cutter and end mill cutter?
Ans.
16. Draw the nomenclature of a milling cutter?
Ans.
17. What are the various types of grinding machine?
Ans.
· Belt grinder
· Bench grinder
· Cylindrical grinder
· Surface grinder
· Tool and cutter grinder
· Jig grinder.
18. Define grinding with neat sketch?
Ans.Removing of metal by
a rotating abrasive wheel.(Very high speed, Shallow cuts)
The wheel action similar to a
milling cutter with very large number of cutting points.
Grinding was first used for making tools and arms.
19. What are the natural abrasive and artificial abrasive?
Ans. a)Natural abrasives
1. Sand stone (quartz)
2. Corundum and Emery
3. Diamond and garnets
b) Artificial abrasives
1.Silicon
Carbide(carborundum)
2. Aluminum
Oxide(Alundum)
3.Cubic Boron
Nitride(CBN)
20. Explain the cutting process of grinding machine?
Ans. Cutting action of grinding wheel:
· Structure of the wheel decides its cutting action.
· Each cutting edge produces small chips in similar action as single point action.
· In edge dull, the large friction forces remove the dull grain and the old grain is replaced by a new one.
· Grade or strength of bond controls removal of grains and the kind of bond and theamount of bond is important.
· The ratio of material removal/ abrasive removal is 40:1 to 80:1 in volume to the wheel loses its shape
· Self-sharpening of a dull wheelmay occur when deeper cuts are taken.
· Optimal value of cut depth for which required cutting power becomes lower and the wheel wear rate provides the wheel with continuous replacement of dull.
21. What are the problems related to grinding process?
PROBLEMS RELATED TO GRINDING
1. BALANCING:
· The high wheel speed
· Not balanced wheels affect the quality of the ground surface because of the vibrations
2. SAFETY PROBLEMS:
· Speed limit (marked on wheels) should be respected
· Cracking of the wheel should be avoided (do not hit or drop)
· Face of the operator protected against grain dislodging
· Wheel should be shielded and dust should be collected and filtered
3. RESIDUAL STRESS:
· Surface of the work builds up residual stress; low chip thickness and lower stress
4. USE OF COLLANTS:
· Cooling & lubrication & collect dust and chips
· Sometimes, without coolants, better finish is obtained.
22. Difference
between Wet grinding and Dry grinding?
Feed material should have low (< 1%) moisture content.
The feed should be inless contact with air (it may absorb moisture during grinding).
The grinding media and the liner inside the mill should not wear off.
Costly filtering equipments are not needed.
Dust control duringgrinding is needed.
WET GRINDING.
Needs less power.
Needs less space.
Minimum dust control only needed.
Needs large quantities of water and good, continuous pumpingsystem.
Generally cheaper than a dry grinding installation.
23. What are the
types of grinding wheels?
· Cup wheel
· Straight wheel
· Cylinder wheel
· Tapered wheel
· Straight cup
· Dish cup
· Saucer wheel
· Diamond wheel
· Diamond Mandrels
24. Explain any four
types of grinding wheel with neat sketch?
A very shallow cup-style grinding wheel. The thinness allows grinding in slots and crevaces. It is used primarily in cutter grinding and jig grinding.
2.Saucer wheel
A special grinding
profile that is used to grind milling cutters and twist drills. It is most
common in non-machining areas, as sawfilers use saucer wheels in the
maintenance of sawblades.
3.Tapered wheel
A straight wheel that
tapers outward towards the center of the wheel. This arrangement is stronger
than straight wheels and can accept higher lateral loads.
4.Cup wheel
A cup wheel as pictured to the right is predominantly used in Tool and Cutter grinders where orientation of the wheel and a slim profile are required. These wheels are used (and dressed) on the side face and have the advantage of producing a truly flat surface on the side of lathe tools. They are used in jig grinders to produce flat surfaces or counter bores.
25. Explain Grinding wheel flanges clamping force?
· It must be high enough to drive the wheel without slippage under the most severe operating conditions of the machine.
· It must not apply to the wheel an excessive compression stress which could weaken the wheel.
· It must not distort the flanges.
26.Draw two types of Taper grinding process?
Ans.
27. Define diamond wheel and explain the
uses?
Ans. A grinding wheel for very hard materials (such as gems or tungsten carbide) using diamond dust as abrasive.
Diamond wheels are used in different-roughness grindings. For coarse grinding, the bond should be softer and the diamonds' quality should be higher, because in this case the diamonds become blunt more easily. The diamond grit should be bigger, normally from 35 grit to 50 grit. For this is coarse grinding and big grit can improve working efficiency. The diamond concentration can be lower.
28. Explain the two
types of method to manufacturing diamond wheel?
The hot pressing method is to directly sinter the diamond segments in molds under a certain pressure in the dedicated sintering press machine, and then fix or connect the diamond segments onto the grinding wheel’s body via high-frequency welding, laser welding or mechanical mosaic method.
29. Define Bond and types of Bonds?
Ans.A bond is an adhesive material used to held abrasive particles together; relatively stable that constitutes a grinding wheel.
Different types of bonds are :
(a)Vitrified bond,
(b)Silicate bond,
(c)Shellac bond,
(d)Resinoid bond,
(e)Rubber bond, and
(f)Oxychloride bond.
30. Identify grinding wheel of WA36K5R1
Ans.
31. Explain about Vitrified Bond?
Ans. • This bond consists of mixture of clay and water.
• Clay and abrasives are thoroughly mixed with water tomake a uniform mixture.
• The mixture is moulded to shape of a grinding wheeland dried up to take it out from mould.
• Perfectly shaped wheel is heated in a kiln just like brickmaking.
• It this way clay vitrifies and fuses to form a porcelain orglass grains.
• High temperature also does annealing of abrasive.
This wheel posses a good strength and porosity to allow high stock removal with coal cutting.
Disadvantage of this type of wheel are, it is sensitive for heat,water, oil and acids. Their impact and bending strengths arealso low. This bond is denoted by symbol ‘V’ in specification.
32.Explain
about Silicate bond and Shellac bond,
b) Shellac
bond are prepared by mixing abrasive with shellac than moulded by rolling and
pressing and then by heating upto 150°C for several hours. This bond exhibit
greater elasticity than other bonds with appreciable strength. Grinding wheels
having shellac bond are recommended for cool cutting on hardened steel and thin
sections, finishing of chilled iron, cast iron, steel rolls, hardened steel
cams and aluminium pistons. This bond is denoted by ‘E’ in specifications.
33.
Explain about Resinoid Bond?
34. Explain
about Rubber bond?
• Rubber bonded wheels are more resilient and have larger abrasive density.
• Used for precision grinding and good surface finish.
Rubber bond is also preferred for making thin wheels with good strength and toughness.
• Associated disadvantage with rubber bond is, these are lesser heat resistant.
• A rubber wheel bonded wheel is denoted by the letter ‘R’.
35.Explain about Oxychloride Bond?
Ans.• These bonds
are processed by mixing abrasives with oxides and chlorides of magnesium.
• The mixture is moulded and baked in a furnace to give shape of a grinding wheel.
• These grinding wheels are used for disc grinding operations. An oxychloride bonded wheel is specified the letter ‘O’.
36.Explain about Structure?
Ans. Abrasive grains are
not packed tightly in the wheel but are disturbed Through the bond. The
relative spacing is referred to as the structure and denoted by the number of
cutting edges per unit area of wheel face as well as by number and size of void
spaces between grains.The primary purpose of structure is to provide clearance
of chip and it may be open or dense. The structure commonly used is denoted by
numbers as follows.
37.Explain aboutGrade?
Ans.The term "grade" as
applied to a grinding wheel refers to the tenacity or hardness with which the
bond holds the cutting points or abrasive grains in place. It does not refer to
the hardness of the abrasive grain. The grade shall be indicated in all bonds
and processes by a letter of the English alphabet.
A denoting
the softest and the letter Z denoting the hardest grade. The term
"soft" or "hard" refer to the resistance a bond offers to
disruption of the abrasives. A wheel from which the abrasive grains can easily
be dislodged is called soft whereas the one which holds the grains more
securely is called hard.The grades are denoted below.
38. Explain aboutGrits?
Ans.The grain or grit number
indicates in a general way the size of the abrasive grains used in making a wheel,
or the size of the cutting teeth, since grinding is a true cutting operation.
Grain size is denoted by a number indicating the number of meshes per liner inch (25.4 mm) of the screen through which the grains pass when they are graded after crushing. The following list ranging from very coarse to very fine includes all the ordinary grain sizes commonly used in the manufacture of grinding wheels.
39. Draw the traverse grinding?
Ans.
40. What are the three ways of grinding operation is done?
Ans. In Feed – moving the
wheel across the surface.
Pluge-cut –
the material rotates as the wheel moves radially into the surface.
Creep feed grinding – the material feed past the wheel.
41. Explain about Silicon Carbide?
Ans. It is also called carbornudum It
is manufactured from 56 parts of silica sand, 34 parts of powdered cake, 2 pats
of salt, 12 parts of saw dust in a long rectangular electric furnace of
resistance type.
There are two types of silicon carbide abrasive green grit
with approximately 97 silicon carbide black grit with approximately 95 silicon
carbide.
It is less harder than diamond and less tough than aluminium
oxide.
It is used for grinding of material of low tensile strength like cemented carbide, stone and ceramic, gray cast iron, brass, bronze, aluminium vulcanized rubber, etc.
42.Explain
about Aluminium Oxide?
43.
Brefily explain about surface grinding machine with types?
Basicallythere are four different types of surfacegrinding machines characterized by the movement of theirtables and the orientation of grinding wheel spindles,
· Horizontal spindle and reciprocating table
· Vertical spindle and reciprocating table
· Horizontal spindle and rotary table
· Vertical spindle and rotary table.
44.Explain about Creep-feed grinding with neat sketch?
Ans. This machine enables
single pass grinding of a surface with a larger down feed but slower table
speed than that adopted for multi-pass conventional surface grinding.
In creep-feed grinding, the entire depth of cut is completed
in one pass only using very small in-feed rates.
45. What is spark out in grinding?
Despite
its potential for high-quality productions, spark-out is time-consuming. While
examining the thermal distortion on ground surface in spark-out, this study
develops a strategy to achieve high flatness on ground surfaces.
A
numerical model is developed to analyze the surface deformations in dry grinding.
Additionally, exactly how set depth of cut, wheel properties and cutting fluid
affects surface profile during spark-out is examined by experiments.
Results
of the study demonstrate that concave distortion of the profiles is reduced
during spark-out with dry grinding, and the profiles turn convex with wet
grinding of steel with a white alumina wheel. Optimum flatness is generally
achieved, when a smaller set depth of cut and cutting fluid are used in the
experiments.
46. Draw the internal and external grinding?
Ans.
47. Explain about polishing?
Ans. Polishing is an abrading process in which small amounts of metal are removed to produce a smooth or glossy surface by application of cushion wheels impregnated or coated with abrasives. Polishing may be used for reduction or smoothing of the surface to a common level for high finish where accuracy is not important or it may be employed for removing relatively large amounts of material from parts of irregular contour. Rough polishing is performed on a dry wheel using abrasives of No. 60 grain (60 grains per linear inch) or coarser. Dry finish polishing is a similar process where No 70. grain to No. 120 grain abrasives are used. Oiling is the term applied to polishing with abrasive finer than No. 120 grain. In this process, the abrasive is usually greased with tallow or a similar substance.
48. Explain about Buffing?
49.Explain about Lapping?
Ans. Lapping, like polishing, is an abrading process in which small amounts of material are removed. Unlike polishing, however, lapping is intended to produce very smooth, accurate surfaces, and is never used instead of polishing or buffing when clearance is the only consideration. Lapping is accomplished by charging metal forms called laps with flour fine abrasives and then rubbing the workpiece with the lap. The lap may be of any shape and may be designed to fit into most power machine tools. The only requirements of the lap are that it be of softer material than the material being lapped, and that it be sufficiently porous to accept the imbedded abrasive grain.
50. Draw the basic principle of Centreless grinding process?
Ans:
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