Crater wear is mainly due to the phenomenon known as
Adhesion of metals
Oxidation of metals
Diffusion of metals
All of these
Correct Answer :
C. Diffusion of metals
Related Questions
The chuck preferred for quick setting and accurate centering of a job is
Four jaw independent chuck
Collect chuck
Three jaw universal chuck
Magnetic chuck
When 3-2-1 principle is used to support and locate a three dimensional work-piece during machining, the number of degrees of freedom that are restricted is
7
8
9
10
In machining metals, chips break due to __________ of work material.
Toughness
Ductility
Elasticity
Work hardening
The work or surface speed for cylindrical grinding varies from
5 to 10 m/min
10 to 20 m/min
20 to 30 m/min
40 to 60 m/min
Green sand mould indicates that
Polymeric mould has been cured
Mould has been totally dried
Mould is green in colour
Mould contains moisture
The abrasive recommended for grinding materials of high tensile strength is
Silicon carbide
Aluminium oxide
Sand stone
Diamond
The angle between the face and flank of the single point cutting tool is known as
Rake angle
Clearance angle
Lip angle
Point angle
Tool life is generally better when
Grain size of the metal is large
Grain size of the metal is small
Hard constituents are present in the microstructure of the tool material
None of the above
What is the type of shielding gas for GTAW (Gas Tungsten Arc Welding) used for carbon steels only called?
Argon H₂
Argon CO₂
Argon Helium
Helium
The obtuse angle, included between the chisel edge and the lip as viewed from the end of a drill, is called
Helix or rake angle
Point angle
Chisel edge angle
Lip clearance angle
If the helix angle of the drill is made _________ 30°, then the torque required to drive the drill at a given feed will be more.
Equal to
Less than
More than
None of these
Larger end cutting edge angle _________ tool life.
Increases
Decreases
Does not effect
None of these
Side rake angle of a single point cutting tool is the angle
By which the face of the tool is inclined towards back
By which the face of the tool is inclined sideways
Between the surface of the flank immediately below the point and a plane at right angles to the centre line of the point of the tool
Between the surface of the flank immediately below the point and a line drawn from the point perpendicular to the base
Work speed of circular electrode of 220 mm diameter for carrying out seam welding at 4 welds per cm on 1.6 mm thick mild steel tube. Welding cycle consists of 3 cycles on and 2 cycles off Power supply is at 50 Hz. Calculate R.P.M. and energy requirement of the above circular electrodes assuming effective resistance between electrodes as 100 ohm.
2.17 rpm, 600 joules
6.8 rpm, 6 joules
5.03 rpm, 600 joules
22 rpm, 600 joules
Quality screw threads are produced by
Thread milling
Thread chasing
Thread cutting with single point tool
Thread casting
The vector sum of cutting velocity and chip velocity is __________ shear velocity.
Equal to
Less than
More than
None of these
The hardness of a grinding wheel is specified by
Brinell hardness number
Rockwell hardness number
Vickers pyramid number
Letter of alphabet
The material which on machining produces chips with built up edge is
Brittle material
Tough material
Hard material
Ductile material
The process of removing metal by a cutter which is rotated in the same direction of travel of workpiece, is called
Up milling
Down milling
Face milling
End milling
Trepanning is an operation of
Making a cone-shaped enlargement of the end of a hole
Smoothing and squaring the surface around a hole
Sizing and finishing a small diameter hole
Producing a hole by removing metal along the circumference of a hollow cutting tool
The cutting force in up milling __________ per tooth movement of the cutter.
Is zero
Is maximum
Decreases from maximum to zero
Increases from zero to maximum
A twist drill is specified by its
Shank, material and diameter
Shank, lip angle and size of flute
Material, length of body and helix angle
Any one of these
The angle formed by the leading edge of the land with a plane having the axis of the drill, is called
Helix or rake angle
Point angle
Chisel edge angle
Lip clearance angle
Cold working of steel is defined as working
At its recrystallisation temperature
Above its recrystallisation temperature
Below its recrystallisation temperature
At two thirds of the melting temperature of the metal
In up-cut milling the work piece is fed
Against the rotating cutter
At angle of 60° to the cutter
In the direction of the cutter
At the right angle to the cutter
The correct sequence of tool materials in increasing order of their ability to retain their hot hardness is
Carbide, ceramic, cermet, borazon
Ceramic, carbide, borazon, cermet
Cermet, carbide, ceramic, borazon
Borazon, ceramic, carbide, cermet
In the relation VTn = C, the value of n for ceramic tools is
0.1 to 0.2
0.20 to 0.25
0.25 to 0.40
0.40 to 0.55
The method of grinding used to produce internal cylindrical holes and tapers, is
Internal cylindrical grinding
Form grinding
External cylindrical grinding
Surface grinding
The cutting speed is minimum while machining _________ with a high speed steel tool.
Cast iron
Mild steel
Brass
Aluminium
A process of removing metal by pushing or pulling a cutting tool is called
Up milling
Down milling
Forming
Broaching