GATE Questions & Answers of Machining and Machine Tool Operations Mechanical Engineering

Using the Taylor’s tool life equation with exponent $ n=0.5, $ if the cutting speed is reduced by 50%, the ratio of new tool life to original tool life is

A grinding ratio of 200 implies that the

An orthogonal cutting operation is being carried out in which uncut thickness is 0.010 mm, cutting speed is 130 m/min, rake angle is $ 15^\circ $ and width of cut is 6 mm. It is observed that the chip thickness is 0.015 mm, the cutting force is 60 N and the thrust force is 25 N. The ratio of friction energy to total energy is __________ (correct to two decimal places).

An electrochemical machining (ECM) is to be used to cut a through hole into a 12 mm thick aluminum plate. The hole has a rectangular cross-section, 10 mm × 30 mm. The ECM operation will be accomplished in 2 minutes, with efficiency of 90%. Assuming specific removal rate for aluminum as 3.44 × $ 10^{-2} $  mm3 /(A s), the current (in A) required is __________ (correct to two decimal places).

Feed rate in slab milling operation is equal to

Metal removal in electric discharge machining takes place through

The preferred option for holding an odd-shaped workpiece in a centre lathe is

Following data correspond to an orthogonal turning of a 100 mm diameter rod on a lathe. Rake angle: $ 15^\circ $ ; Uncut chip thickness: 0.5 mm; nominal chip thickness after the cut: 1.25 mm. The shear angle (in degrees) for this process is _______ (correct to two decimal places).

Taylor’s tool life equation is used to estimate the life of a batch of identical HSS twist drills by drilling through holes at constant feed in 20 mm thick mild steel plates. In test 1, a drill lasted 300 holes at 150 rpm while in test 2, another drill lasted 200 holes at 300 rpm. The maximum number of holes that can be made by another drill from the above batch at 200 rpm is ______ (correct to two decimal places).

A circular hole of 25 mm diameter and depth of 20 mm is machined by EDM process. The material removal rate (in mm3/min) is expressed as

                                                                                          $ 4\times10^4\;IT^{-1.23} $ ,

where $ I=300 $ A and the melting point of the material, $ T=1600^\circ C $ . The time (in minutes) for machining this hole is ________ (correct to two decimal places)

Match the processes with their characteristics.

Process  Characteristics 
P: Electrical Discharge Machining 1. No residual stress
Q: Ultrasonic machining 2. Machining of electrically conductive materials
R: Chemical machining 3. Machining of glass
S: Ion Beam Machining 4. Nano-maching

 

Metric thread of 0.8 mm pitch is to be cut on a lathe. Pitch of the lead screw is 1.5 mm. If the spindle rotates at 1500 rpm, the speed of rotation of the lead screw (rpm) will be______________

A block of length 200 mm is machined by a slab milling cutter 34 mm in diameter. The depth of cut and table feed are set at 2 mm and 18 mm/ miniute, respectively. Considering the approch and the over travel of the cutter to be same, the minimum estimated machining time per pass is __________ miniutes.

Two cutting tools with tool life equations given below are being compared:
Tool 1: VT 0.1 = 150
Tool 2: VT 0.3 = 300
Where V is cutting speed in m/minute and T is tool life in minutes. The breakeven cutting speed beyond which Tool 2 will have higher tool life is _________ m/minute

Which one of the following statements is TRUE for the ultrasonic machining (USM) process?

During the turning of a 20 mm-diameter steel bar at a spindle speed of 400 rpm, a tool life of 20 minute is obtained. When the same bar is turned at 200 rpm, the tool life becomes 60 minute. Assume that Taylor’s tool life equation is valid. When the bar is turned at 300 rpm, the tool life (in minute) is approximately

In an orthogonal machine with a tool of 9° orthogonal rake angle, the uncut chip thickness is 0.2 mm. The chip thickness fluctuates between 0.25 mm and 0.4 mm. The ratio of the maximum shear angle to the minimum shear angle during machine is____________

The non-traditional machining process that essentially requires vacuum is

In an orthogonal cutting process the tool used has rake angle of zero degree. The measured cutting force and thrust force are 500 N and 250 N, respectively. The coefficient of friction between the tool and the chip is _________

The tool life equation for HSS tool is $VT^{0.14}f^{0.7}d^{0.4}$ = Constant. The tool life (T) of 30 min is obtained using the following cutting conditions:
$V=45\mathrm m/\min,f=0.35\mathrm{mm},d=2.0\mathrm{mm}$
If speed $ (\mathrm V) $, feed $ (\mathrm f) $ and depth of cut $ (\mathrm d) $ are increased individually by 25%, the tool life (in min) is

The following data is applicable for a turning operation. The length of job is 900 mm, diameter of job is 200 mm, feed rate is 0.25 mm/rev and optimum cutting speed is 300 m/min. The machining time (in min) is __________

In an ultrasonic machining (USM) process, the material removal rate (MRR) is plotted as a function of the feed force of the USM tool. With increasing feed force, the MRR exhibits the following behavior:

For a certain job, the cost of metal cutting is Rs.18C/V and the cost of tooling is Rs.270C/(TV), where C is constant, V is the cutting speed in m/min and T is the tool life in minutes. The Taylor's tool life equation is VT0.25=150. The cutting speed (in m/min) for the minimum total cost is ___________

The surface irregularities of electrodes used in an electrochemical machining (ECM) process are 3 μm and 6 μm as shown in the figure. If the work-piece is of pure iron and 12V DC is applied between the electrodes, the largest feed rate is ___________mm/min.

  Conductivity of the electrolyte     $0.02\;\mathrm{ohm}^{-1}\mathrm{mm}^{-1}$  
  Over-potential voltage   1.5 V
  Density of iron   $7860\;\mathrm{kg}/\mathrm m^3$
  Atomic weight of iron   55.85 gm

 

Assume the iron to be dissolved as $\mathrm{Fe}^{+2}$ and the Faraday constant to be 96500 Coulomb.

 

 

In a wire-cut EDM process the necessary conditions that have to be met for making a successful cut are that

Internal gears are manufactured by

For an orthogonal cutting operation, tool material is HSS, rake angle is 22°, chip thickness is 0.8 mm, speed is 48 m/min and feed is 0.4 mm/rev. The shear plane angle (in degrees) is

In a single point turning operation with cemented carbide tool and steel work piece, it is found that the Taylor’s exponent is 0.25. If the cutting speed is reduced by 50% then the tool life changes by ______ times.

Under certain cutting conditions, doubling the cutting speed reduces the tool life to 116th of the original. Taylor’s tool life index (n) for this tool-workplace combination will be ____.

An orthogonal turning operation is carried out under the following conditions; rake angle = 5o, spindle rotational speed = 400 rpm, axial feed = 0.4 m/min and radial depth of cut = 5 mm. The chip thickness , $ t_c $ , is found to be 3 mm. The shear angle (in degrees) in this turning process is ____.

The primary mechanism of material removal in electrochemical machining (ECM) is

A single point cutting tool with 0o rake angle is used in an orthogonal machining process. At a cutting speed of 180 m/min the thrust force is 490 N. If the coefficient of friction between the tool and the chip is 0.7, then the power consumption (in kW) for the machining operation is _______.

A resistance capacitance relaxation circuit is used in an electrical discharge machining process. The discharge voltage is 100 V. At a spark cycle time of 25 μs the average power input required is 1 kW. The capacitance (in μF) in the circuit is

In a machining operation, if the generatrix and directrix both are straight lines, the surface obtained is

Orthogonal turning of a mild steel tube with a tool of rake angle 10º is carried out at a feed of 0.14 mm/rev. If the thickness of the chip produced is 0.28 mm, the values of shear angle and shear strain will be respectively

A shaft of length 90 mm has a tapered portion of length 55 mm. The diameter of the taper is 80 mm at one end and 65 mm at the other. If the taper is made by tailstock set over method, the taper angle and the set over respectively are

The main cutting force acting on a tool during the turning (orthogonal cutting) operation of a metal is 400 N. The turning was performed using 2 mm depth of cut and 0.1 mm/rev feed rate. The specific cutting pressure (in N/mm2) is

During pure orthogonal turning operation of a hollow cylindrical pipe, it is found that the thickness of the chip produced is 0.5 mm. The feed given to the zero degree rake angle tool is 0.2 mm/rev. The shear strain produced during the operation is _______

If the Taylor’s tool life exponent n is 0.2, and the tool changing time is 1.5 min, then the tool life (in min) for maximum production rate is _______

Match the Machine Tools (Group A) with the probable Operations (Group B):

Group A Group B
P: Centre Lathe 1: Slotting
Q: Milling 2: Counter-boring
R: Grinding 3: Knurling
S: Drilling 4: Dressing

The following four unconventional machining processes are available in a shop floor. The most appropriate one to drill a hole of square cross section of 6 mm × 6 mm and 25 mm deep is

A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together is equal to the radius of drill. The drilling time (in minute) is

The process utilizing mainly thermal energy for removing material is

A straight turning operation is carried out using a single point cutting tool on an AISI 1020 steel rod. The feed is 0.2 mm/rev and the depth of cut is 0.5 mm. The tool has a side cutting edge angle of 60°. The uncut chip thickness (in mm) is _______

Cutting tool is much harder than the workpiece. Yet the tool wears out during the tool-work interaction, because

Which pair of following statements is correct for orthogonal cutting using a single-point cutting tool?

P. Reduction in friction angle increases cutting force
Q. Reduction in friction angle decreases cutting force
R. Reduction in friction angle increases chip thickness
S. Reduction in friction angle decreases chip thickness

Two separate slab milling operations, 1 and 2, are performed with identical milling cutters. The depth of cut in operation 2 is twice that in operation 1. The other cutting parameters are identical. The ratio of maximum uncut chip thicknesses in operations 1 and 2 is ______

The principle of material removal in Electrochemical machining is

A cast iron block of 200 mm length is being shaped in a shaping machine with a depth of cut of 4 mm, feed of 0.25 mm/stroke and the tool principal cutting edge angle of 30°. Number of cutting strokes per minute is 60. Using specific energy for cutting as 1.49 J/mm3, the average power consumption (in watt) is _______

A steel bar 200 mm in diameter is turned at a feed of 0.25 mm/rev with a depth of cut of 4 mm. The rotational speed of the workpiece is 160 rpm. The material removal rate in mm3/s is

Two cutting tools are being compared for a machining operation. The tool life equations are:
Carbide tool: VT1.6 = 3000
HSS tool: VT 0.6 = 200
where V is the cutting speed in m/min and T is the tool life in min. The carbide tool will provide higher tool life if the cutting speed in m/min exceeds

During the electrochemical machining (ECM) of iron (atomic weight = 56, valency = 2) at current of 1000 A with 90% current efficiency, the material removal rate was observed to be 0.26 gm/s. If Titanium (atomic weight = 48, valency = 3) is machined by the ECM process at the current of 2000 A with 90% current efficiency, the expected material removal rate in gm/s will be

In orthogonal turning of a bar of 100 mm diameter with a feed of 0.25 mm/rev, depth of cut of 4 mm and cutting velocity of 90 m/min, it is observed that the main (tangential) cutting force is perpendicular to the friction force acting at the chip-tool interface. The main (tangential) cutting force is 1500 N.
The orthogonal rake angle of the cutting tool in degree is

In orthogonal turning of a bar of 100 mm diameter with a feed of 0.25 mm/rev, depth of cut of 4 mm and cutting velocity of 90 m/min, it is observed that the main (tangential) cutting force is perpendicular to the friction force acting at the chip-tool interface. The main (tangential) cutting force is 1500 N.

The normal force acting at the chip-tool interface in N is

In abrasive jet machining, as the distance between the nozzle tip and the work surface increases, the material removal rate

Details pertaining to an orthogonal metal cutting process are given below.

Chip thickness ratio 0.4
Undeformed thickness 0.6 mm
Rake angle +10°
Cutting speed 2.5 m/s
Mean thickness of primary shear zone 25 microns

The shear strain rate in s–1 during the process is

In a single pass drilling operation, a through hole of 15 mm diameter is to be drilled in a steel plate of 50 mm thickness. Drill spindle speed is 500 rpm, feed is 0.2 mm/rev and drill point angle is 118°. Assuming 2 mm clearance at approach and exit, the total drill time (in seconds) is

A single-point cutting tool with 12o rake angle is used to machine a steel work-piece. The depth of cut, i.e. uncut thickness is 0.81 mm. The chip thickness under orthogonal machining condition is 1.8mm. The shear angle is approximately

Match the following non-traditional machining processes with the corresponding material removal mechanisms :

Machining process Mechanism of material removal
P. Chemical machining 1.Erosion
Q. Electro-chemical machining 2.Corrosive reaction
R. Electro-discharge machining 3.Ion displacement
S. Ultrasonic machining 4.Fusion and vaporization

For tool A, Taylor’s tool life exponent (n) is 0.45 and constant (K) is 90. Similarly for tool B, n=0.3 and K=60. The cutting speed (in m/min) above which tool A will have a higher tool life than tool B is

Friction at the tool-chip interface can be reduced by

Minimum shear strain in orthogonal turning with a cutting tool of zero rake angle is

Electrochemical machining is performed to remove material from an iron surface of 20 mm × 20 mm under the following conditions:

Inter electrode gap    = 0.2mm
Supply voltage DC    = 12V
Specific resistance of electrolyte  = 2 Ω cm
Atomic weight of Iron    = 55.85
Valency of Iron     = 2
Faraday 's constant    = 96540 Coulombs

The material removal rate (in g/s) is

In a machining experiment, tool life was found to vary with the cutting speed in the following manner:

Cutting speed (m/min) Tool life (minutes)
60 81
90 36

The exponent (n) and constant (k) of the Taylor’s tool life equation are

In a machining experiment, tool life was found to vary with the cutting speed in the following manner:

Cutting speed (m/min) Tool life (minutes)
60 81
90 36

What is the percentage increase in tool life when the cutting speed is halved?

Internal gear cutting operation can be performed by

In a single point turning tool, the side rake angle and orthogonal rake angle are equal. φ is the principal cutting edge angle and its range is 0° ≤ φ ≤ 90°. The chip flows in the orthogonal plane. The value of φ is closest to

A researcher conducts electrochemical machining (ECM) on a binary allow (density 6000 kg/m3) of iron (atomic weight 56, valency 2) and metal P (atomic weight 24, valency 4). Faraday’s constant = 96500 coulomb/mole. Volumetric material removal rate of the alloy is 50 mm3/s at a current of 2000 A. The percentage of the metal P in the alloy is closest to

The figure shows an incomplete schematic of a conventional lathe to be used for cutting threads with, different pitches. The speed gear box Uv is shown and the feed gear box Us is to be placed. P, Q, R and S denote locations and have no other significance. Changes in Uv should NOT affect the pitch of the thread being cut and changes in Us should NOT affect the cutting speed.

The correct connections and the correct placement of Us are given by

Orthogonal turning is performed on a cylindrical workpiece with shear strength of 250 MPa. The following conditions are used: cutting velocity is 180 m/min, feed is 0.20 mm/rev, depth of cut is 3 mm, chip thickness ratio = 0.5. The orthogonal rake angle is 7°. Apply Merchant’s theory for analysis.

The shear plane angle (in degrees) and the shear force respectively are

Orthogonal turning is performed on a cylindrical workpiece with shear strength of 250 MPa. The following conditions are used: cutting velocity is 180 m/min, feed is 0.20 mm/rev, depth of cut is 3 mm, chip thickness ratio = 0.5. The orthogonal rake angle is 7°. Apply Merchant’s theory for analysis.

The cutting and frictional forces, respectively, are

In orthogonal turning of a low carbon steel bar of diameter 150 mm with uncoated carbide tool, the cutting velocity is 90 m/min. The feed is 0.24 mm/rev and the depth of cut is 2 mm. The chip thickness obtained is 0.48mm. If the orthogonal rake angle is zero and the principal cutting edge angle is 90°, the shear angle in degree is

In electrodischarge machining (EDM), if the thermal conductivity of tool is high and the specific heat of work piece is low, then the tool wear rate and material removal rate are expected to be respectively

In orthogonal turning of medium carbon steel, the specific machining energy is 2.0 J/mm3. The cutting velocity, feed and depth of cut are 120 m/min, 0.2 mm/rev and 2 mm respectively. The main cutting force in N is

In orthogonal turning of low carbon steel pipe with principal cutting edge angle of 90°, the main cutting force is 1000 N and the feed force is 800 N. The shear angle is 25° and orthogonal rake angle is zero. Employing Merchant’s theory, the ratio of friction force to normal force acting on the cutting tool is

Match the most suitable manufacturing processes for the following parts.

  Parts Manufacturing Processes
P. Computer chip 1. Electrochemical Machining
Q. Metal forming dies and molds 2. Ultrasonic Machining
R. Turbine blade 3. Electrodischarge Machining
S. Glass 4. Photochemical Machining

A low carbon steel bar of 147 mm diameter with a length of 630 mm is being turned with uncoated carbide insert. The observed tool lives are 24 min and 12 min for cutting velocities of 90 m/min and 120 m/min respectively. The feed and depth of cut are 0.2 mm/rev and 2 mm respectively. Use the unmachined diameter to calculate the cutting velocity.

When tool life is 20 min, the cutting velocity in m/min is

A low carbon steel bar of 147 mm diameter with a length of 630 mm is being turned with uncoated carbide insert. The observed tool lives are 24 min and 12 min for cutting velocities of 90 m/min and 120 m/min respectively. The feed and depth of cut are 0.2 mm/rev and 2 mm respectively. Use the unmachined diameter to calculate the cutting velocity.

Neglect over – travel or approach of the tool. When tool life is 20 min, the machining time in min for a single pass is