Mechanical Engineering

The distance a screw thread advances axially for one complete revolution is called Lead

Square thread is using for mechanical screw jack.














Rag bolt is a Foundation bolt











Types of Keys

Tangential keys are used when very high torque of impact type to be transmitted in both direction of rotation

M30 x 2 for a bolt represents _ Metric threads of 30mm outside diameter and 2mm pitch.

The washer is specified by inner diameter

Wing nuts are used in light duty assembly which require frequent removal or fixing.

• In a riveted joint the tensile, shearing and crushing stresses are based on the diameter of drilled hole
• A welded joint as compared to riveted joint, has more strength

The ratio of the pitch diameter to the number of teeth of the gear is called Module

The profile of a gear tooth is in the form of Involutes

The size of the gear is usually specified by pitch circle diameter

✓ The point of contact of two pitch circles of mating gears is called Addendum



✓ The radial distance of the tooth below pitch circle is called Dedendum



Vices

Bench vices, also known as woodworking or engineer's vices

The box nut of a bench vice is made of Phosphorus bronze

• The vice clamps are used to protect the finished surfaces
• The size of an engineer’s vice is specified by the width of the jaw

Leg vice is using for forging works

Toolmaker vises are precision ground on all four sides




Files 

Rasp cut file is used for filing wood  determined by spacing of teeth





File Grade -> Very Smooth -> Smooth -> Second Cut -> Bastard -> Rough

✓ The term surface finish refers to the Roughness or smoothness of a surface

✓ The files are made of high carbon steel

✓ A Second cut file is used for bringing the jobs close to the finishing size.

The Mallet hammer made of wood

The portion of the hammer which is not hardened is the Cheek

Four common types of cold chisels.

Flat chisel, the most widely known type, which is used to cut bars and rods to reduce surfaces and to cut sheet metal that is too thick or difficult to cut with tin snips

Cross cut chisel is used for cutting grooves and slots. The blade narrows behind the cutting edge to provide clearance.

Round nose chisel is used for cutting semi-circular grooves for oil ways in bearings.

Diamond point chisel is used for cutting V shaped grooves

• The chisel will dig into the material when the angle of inclination is more
• A slight convexity is given to cutting edge to prevent digging on the ends.
• The process of beveling at the end is calling Counter boring

Vernier caliper- Least count  0.1 mm

Vernier metric micrometer - Least count  0.001 mm

Screw gauge/ metric micro meter - Least count  0.01 mm

Vernier bevel protractor – Least count 5 minute (1°/12)

Vernier height gauge - Least count  0.02mm

A sine bar is used for finding the angle of a taper job










Drilling Machines

Pneumatic hand drilling machine operated by air or gas under pressure

A service petroleum pipe line flange is to be drilled, we will choose Pneumatic hand drilling machine

Electrical hand drilling machine

The purpose of Dressing is to restore the cutting action of the grinding wheel

                              Sensitive drilling machine

The drift is used for drilling machine is removing the drill from the machine spindle



Soluble oil is the suitable cutting fluid for drilling mild steel

The point angle of standard drill is 118°

The reamer size should be less than the drill size (Drill size for 10mm reamer is 9.75mm)

The distance, which the cutting edge of a tool passes over the material in a minute, while machine is known as Cutting speed



Jigs and Fixture

The jig is used for guiding the cutting tool (like a drill bit), a fixture never comes into direct contact with the cutting tool

The production of flat vertical surfaces on both sides of a workpiece is called Straddle milling

 Gang milling is the term applied to an operation in which two or more milling cutters are mounted on the same arbor and used when cutting horizontal surfaces. All cutters may perform the same type of operation or each cutter may perform a different type of operation.

End milling is the most versatile form of milling that can be used to machine slots, shoulders, die cavities, contours, and profiles. An end milling process consists of a cylindrical cutter that has multiple cutting edges on both its periphery and its tip.

Form milling is the process of machining special contours composed of curves and straight lines, or entirely of curves, at a single cut

A single angle milling cutter is used for angular surfaces, such as chamfers, serrations, and grooves.

The lathe bed is made of Grey Cast Iron

Four jaw chuck is using for clamping irregular shaper work on lathe

A lathe dog, also known as a lathe carrier, is a device that clamps around the workpiece and allows the rotary motion of the machine's spindle to be transmitted to the workpiece. A carrier is most often used when turning between centers on a lathe, but it may be used on dividing heads or any similar situation.

A lathe faceplate is a basic work holding accessory for a wood or metal turning lathe. It is a circular metal plate which fixes to the end of the lathe spindle.

In a lathe machine internal and external taper turning can be done by swivelling the compound slide








✓ When a tool is set above the center line of lathe the front clearance decreases

The ability of a tool material to resist shock or impact forces is known as Toughness




Wear resistance is defined as the ability of stone to resist comprehensive external forces such as abrasion, edge cutting and impact etc.

Wear resistance also known as

• Abrasion resistance
• Endurance
• Durability
• Wearability
• Resistance to wear
• wearing quality

Material hardness is the property of the material which enables it to resist plastic deformation or the ability of a metal to cut another metal.

The term machinability refers to the ease with which a metal can be cut (machined) permitting the removal of the material with a satisfactory finish at low cost.

Discontinuous chips tends to be formed when one or more or the following conditions exist:

1.     Brittle material, such as cast iron and bronze.

2.     Large chip thickness

3.     Low cutting speed

4.     Small rack angle

✓ If the metals are ductile and cutting speed are high, then continues chips are formed

The part of the Universal surface gauge the Guide pin will helps to draw the parallel line along the datum edge

The reference surface during marking is provided by marking table surface

Electro discharge machining (EDM) process also known as spark machining

Slitting Machine is using for cutting a sheet of material in a straight line along the length

Embossing machines cut materials such as thin plastic into certain shapes, foam, paper, and fabric.

Perforators are commonly used for creating coupons

The punching marks on the lines drawn during marking off are known as Witness marking

In honing process, the movement of spindle is Vertical & reciprocating.

In Foundry, Oil sand is used for making cores.

Internal Combustion Engine

• In automotive usage, scavenging is the process of pushing exhausted gas.

The loud pulsating noise heard within the cylinder of an IC engine is known as Detonation

• Mechanical efficiency is the ratio of break power to the indicated power of an IC engine
• Brake Thermal Efficiency is defined as break power of a heat engine as a function of the thermal input from the fuel.
• The relative efficiency of an I. C. engine is the ratio of the indicated thermal efficiency to the air standard efficiency
• Indicated thermal efficiency is define as the ratio of the indicated power of the engine to the fuel power.

Supercharging

Super charging is the process of increase the pressure of air by using compressors

• It is the process of increasing the mass or density of air fuel mixture in S.I. Engine or air in C.I. Engine sucked into the engine cylinder.
• It is done with the help of compressor or blower called as supercharger.
• In S.I engine it is mounted before carburetor which reduce the size of carburetor.

The Thermostat is a metallic capsule containing a material that expand with heat such wax (or they also use liquid alcohol because when it evaporates its volume expand also). The role of the thermostat is to maintain the circulation of water inside of the engine block when the engine is started in a cold state in a manner that the normal functioning temperature of the engine is attended quickly. After reaching this temperature (about 80 °C), the water's temperature continue to increase so that the thermostat expand and open progressively the valve permitting the water to flow in the radiator for cooling.

• In an IC engine the thermostat is essential component in the Cooling system

The irregularities in the surface texture due to the inherent action of production process is called Roughness

Roughness values  (ISO 1302:1996)
N1	0.025 µm
N2	0.050 µm
N3	0.10 µm
N4	0.20 µm
N5	0.40 µm
N6	0.80 µm
N7	1.60 µm
N8	3.20 µm
N9	6.30 µm
N10	12.5 µm
N11	25 µm
N12	50 µm

Scotch yoke mechanism is an inversion of double slider crank chain mechanism

Old harm coupling is used for while two shaft axis are parallel but not in same alignment.

Muff coupling is used for while two shaft axis are parallel and in same alignment.

Flange coupling is used for while two shaft axis are parallel and in same alignment. And heavy torque transfer

Sleeve coupling is the simplest type of rigid coupling.

The portion of the shaft carried in the plane bearing is often referred as Journal

The external threads on G.I pipes are cut easily by Dies and die stocks

✓ The Fast pulley is a pulley which has fitted on the shaft

✓ The Loose pulley runs freely on the shaft, it takes care of the idling time and does not transmit any power.

✓ The pulley for flat belt is generally made convex and this is called Crowning

✓ The actual difference caused between the surface speed of the belt and pulley is called Slip

✓ In V belt specification, c3048 IS:2494, 3048 means Nominal inside length in mm

Dwell period of a cam the follower does not move

Reciprocating pump is suitable for high head and less discharge

Cam clamps are used for holding small pieces where you don't need much pressure

Wedge clamp works on the principle of inclined planes

Toggle clamp has a single clamping plate and is designed to hold a workpiece down on a work surface, such as a bench top. The clamp uses a fast-action mechanism

Latch Clamps is for applications where heavy duty Latch type clamping

Feeler gauge - A gauge consisting of a number of thin blades for measuring narrow gaps or clearances.

It is used to check the gap between the matching parts.

Snap gage - A snap gage is a form of go/no go gauge. It is a limit gage with permanently or temporarily fixed measurement aperture which is used to quickly verify

Plug gages - Plug Gauges are measurement tools used for checking diameters of inside and outside, threads, grooves, cones, key ways, and chamfers.

✓ A plug gauge which has its ‘Go’ and ‘No Go’ sizes on the same end is known as Progressive type plug gauge.

Types of Plug Gauges

• Solid type
• Renewable type - taper inserted type
• Fastened type - single ,double ended
• Flat type
• Progressive type
• Pilot plug gauge
• Combined dual purpose type

Clinometer is using for sensitive angle measuring

Furnaces

The process of introducing carbon into low carbon steel in order to produce a hard surface is known as Carburizing

Pig iron refined in a cupola furnace produces Cast iron

Wrought iron is produced by Pudding process

The Bessemer process was the first inexpensive industrial process for the mass production of steel from molten pig iron before the development of the open hearth furnace

Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel.


Types of Heat treatment

• Annealing
• Normalizing
• Quenching or Hardening
• Tempering
• Surface Hardening
• Case Hardening
• Austempering
• Marquenching
• Ausforming

The purpose of given heat treatment is

• To relieve internal stress
• To improve machinability
• To refine grain size
• To soften the material
• To increase resistance to wear and corrosion
• To improve ductility and toughness
• To cut miscellaneous metal
• To change the chemical composition

Fit, Tolerance, Deviation & Allowance

➢ Fit is the relationship that exists between two mating parts, a hole and shaft, with respect to their dimensional differences before assembly.

➢ An intentional difference between the hole dimensions and shaft dimensions for any type of fit is called Allowance

➢ Tolerance is the difference between the upper limit and lower limit of daviation.

➢ Upper Deviation is the algebraic difference between the maximum size and the basic size.

➢ Lower Deviation is the algebraic difference between the minimum size and the basic size.

• The system said to be bilateral tolerance if the Tolerance is in two direction
• The notation 70H6/ g5 means – Basic size is 70mm and tolerance grade of hole is 6 and shaft is 5

 Most suitable cutting flame is oxidizing flame