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What is Machine Drawing?
A machine drawing may be defined as the representation of a machine component or machine by lines according to certain set rules.
Draw symbol for First angle projection.
What are sectional view and its uses?
The view after cutting the object in order to show the inner details by an imaginary cutting plane is known as sectional view.
The sectional views are very important in engineering drawing, as they help in manufacturing and explaining the construction of complicated machines and their parts.
What is cutting plane or sectional plane?
The imaginary plane by which the object is assumed to be cut is called the cutting plane or sectional plane.
What is a sectional line or hatchings?
The line used to represent the material which has been cut by the cutting plane is called section lines or hatchings.
What are the types of sectional views?
The following types of sectional views are commonly used in engineering practice:
Full sectional view, and
Half view.
What are the important sections used in engineering drawing?
The following are the important sections which are mostly used in engineering drawing:
Partial section
Offset section
Revolved section
Removed section
Aligned section.
What do you mean by screw threads and give its practical application?
The helical groove cut on the surface of a cylindrical piece for fastening parts or power transmission is known as screw threads.
It is used in bolts, nuts, machine screws, stud, foundation bolts and other similar parts employed for fastening.
What are multi-start threads? Where these are used and why?
When two or more helices forming the threads run side by side on the cylindrical surface, it is called multi- start threads.
It’s used wherever quick motion is required and application of great Force is not allowed e.g. on fountain pens, bottles, tooth –paste caps, valves etc. impart quick action in opening and closing.
What are the forms of screw threads?
Triangular or “V” form
Square form.
Define Fasteners.
The devices which are used for joining two or more parts of a machine or structure known as fasteners e.g. rivets, bolts and nuts, screws, etc.
What is fastening and states its type?
The process of joining two or more parts of a machine or structure by means of various devices.
There are two types of fastenings used in engineering practice:
Permanent
Temporary.
What is Nut and give its types?
A device used with a bolt or stud to join two or more parts together temporarily is known as nut.
The following are the important form of nuts used:
Hexagonal
Square
Cap
Cylindrical
Wing
What is boltand give its types?
A cylindrical piece with head on one end and threads on the other end is called a bolt.
The following are the important form of bolts used:
Hexagonal
Square
Cylindrical
Cup headed
T – headed
Hook bolt
What is stud and where it is used?
A cylindrical rod, threaded on both ends and plain in the middle is known as stud. It is used where sufficient space for bolt-head and nut is not available.
Studs are commonly used for screwing of engine cylinder cove to a cylinder casting, stop valves, etc.
Define washers and give its types.
A washer is a flat circular disc of metal having a hole in the center for inserting the bolt or stud. The hole is slightly larger in diameter than bolt or stud.
The following are two main types of washers:
Ordinary washer
Spring washer
What are keys? Give its types?
A metal piece inserted between a shaft and wheel hub in an axial direction to prevent their relative movements is known as key.
It’s mainly classified into two they are:
Taper key
Taper sunk, saddle key, flat key, gib head key.
Parallel or feather key.
Parallel sunk key, peg key, single head key, double head key, spline key
What are key ways?
The axial groove cut in the shaft or in the hub for fixing the key is known as key way.
What are cotters and why they are used?
A cotter, is a flat wedge shaped metal piece of rectangular cross-section. It is uniform in thickness but has taper in width throughout its length. The taper may be on one side or both side.
Cotters are used to join two parts of bars which are subjected to tensile or compressive force e.g. in joining of piston rod with crosshead, valve rod end and foundation bolts etc.
Define coupling?
A coupling is a device used to connect or “couple” together two shafts to transmit power from one rotating shaft to another.
What do you mean by shaft coupling and give its types?
The joining of two or more shaft by means of flanges, bolts, nuts etc. in order to increase their length is known as shaft coupling.
It’s mainly divided into two types they are:
Rigid couplings
Non – rigid or flexible couplings.
What is rigid and flexible coupling?
Rigid coupling:
Rigid coupling connect the two shafts rigidly in axial alignment.
Flexible coupling:
Flexible coupling is used to couple two shafts which are slightly out of line or which requires slightly relative angular movement. It is commonly used as direct coupling device to minimize starting shock. E.g. when electric motor is directly coupled to machine.
When Universal couplings are used?
Universal coupling is used to couple two shafts whose axes are not in line with each other, but intersect at a point.
What do you mean by a bearing and its types
The devices which are used for supporting the long shafts are known as bearings.
Bearings are different types depending upon the construction and direction of load acting upon them, but following are the three main types:
Journal bearing
Thrust bearing
Foot step bearings.
What do you meant by swivel bearing?
Swivel bearing is used to support and adjust itself the position of the shaft when there is possibility of slight misalignment.
What do you mean by welding and write its applications
The process of joining two or more metal parts permanently by the application of heat is known as welding.
Welding process is used in the manufacturing of automobile parts, aircrafts, road cars and structural work.
What are the various types of welding?
Welding may be classified under two main headings in engineering:
Plastic or pressure welding
Fusion or Non- pressure welding.
Define fit, limits and tolerance?
The two extreme permissible sizes between which the actual size lies are called limits.
It is defined as the amount of variation permitted to a basic size. The difference between maximum and minimum limits of a basic size is called tolerance.
The relationship existing between the mating surfaces of the parts because of the differences in their dimensions is called fit.
Define geometrical tolerances.
The geometry variations are called form variation and the location variations are called position variation. Specifying of the permissible variations for both form and position using symbols and letters is called geometrical tolerance.
Types of Geometrical Tolerance and Symbols
Geometrical tolerance is of three types namely
a) Form tolerance
b) Position tolerance
c) Run out tolerance
Types of geometrical tolerances and characteristics to be tolerated SYMBOL
Single features Form tolerance Straightness ____
Flatness
Circularity (Roundness)
Related features Cylindricity
Profile of any line
Profile of any surface
Related features Position tolerance Location tolerances Position
Concentricity
Symmetry
Orientation tolerances Parallelism
Perpendicularity
Angularity
Run out tolerances Circular run out
Total run out
Define rivets and its applications.
A rivet is a round rod made either from mild steel or non-ferrous materials such as copper, aluminium, etc.
Define riveted joints and its application.
A riveted joint is a permanent type of fastener used to join the metal plates or rolled steel sections together. Riveted joints are extensively used in structural works such as bridges and roof trusses and in the construction of pressure vessels such as storage tanks, boilers, etc.
What are the disadvantages of riveted joints?
More metal is removed while making of the holes, which weakens the working cross sections.
Weight of the rivets increases the weight of the riveted members.
What are the type of riveted joints?
Lap joints
Butt joints
Diamond or lozenze joint.
Define welding.
Welding is the process of fastening the metal parts together permanently. Both the ferrous and non- ferrous metal are used for welding.
Types of welding
Pressure welding
Resistance welding.
Fusion welding.
Gas and arc welding.
What are the types of welded joints?
Butt joint
Lap joint
Corner joint
Tee joint
Edge joint
Why Limits & Fits?
Exact size is impossible to achieve.
Establish boundaries within which deviation from perfect form is allowed but still the design intent is fulfilled.
Enable interchangeability of components during assembly.
Define of Limits.
The maximum and minimum permissible sizes within which the actual size of acomponent lies are called Limits.
Define Tolerance.
It is impossible to make anything to an exact size, therefore it is essential to allow adefinite tolerance or permissible variation on every specified dimension.
Why Tolerances are specified?
Variations in properties of the material being machined introduce errors.
The production machines themselves may have some inherent inaccuracies.
What is FIT?
Fit is an assembly condition between ‘Hole’ & ‘Shaft’.
When two parts are to be assembled, the relation resulting from the difference between their sizes before assembly is called a fit.