Maharashtra HSC Multi-Skill General Engineering (NSQF) cheat sheet

Personal protective equipment is selected by hazard: safety goggles for grinding and chipping, face shield over goggles for cutting-wheel work, leather gloves for handling hot or rough stock (never near rotating spindles), safety shoes for overhead and heavy-load work, ear plugs or muffs above roughly 85 dB(A).

Machine guards must be in place before start-up; the emergency stop is checked at the start of every shift, and no adjustment, measurement, or swarf removal is done while a machine is running.

First aid for a foreign body in the eye: never rub; flush with clean water or eyewash for at least 15 minutes and refer to a doctor; for chemical splash flush continuously and remove contaminated clothing.

Fire classes and extinguishers: Class A solid fuels use water or foam; Class B flammable liquids use foam, dry powder, or CO2; Class C gases use dry powder; electrical fires use CO2 or dry powder, never water or foam.

Hand tools: a spanner must fit the nut flats fully; files are used with a handle and a steady forward stroke with pressure, released on the return stroke; chisels are struck with a mallet, and mushroomed heads are ground off.

Bench work sequence for a flat file job: mark out with a scriber and datum surface, rough file across the work, finish file along the work, check flatness with a straight edge and squareness with a try square.

Drilling safety rules: clamp the work or use a machine vice, centre-punch the location, use the correct drill speed (lower for large diameter and hard material), clear chips with a brush, and withdraw the drill before stopping.

Housekeeping and lifting: keep aisles and walkways clear, store flammable liquids in closed marked containers, and lift with bent knees and a straight back keeping the load close to the body.

Permit-to-work logic: hot work, confined-space entry, and work at height require a signed permit, gas test where applicable, and a stand-by person before the task begins.

Standard sheet sizes in the ISO A series halve in area at each step: A0 is 841 x 1189 mm, A1 594 x 841 mm, A2 420 x 594 mm, A3 297 x 420 mm, A4 210 x 297 mm.

Scale = drawing length / actual length; a representative fraction of 1:5 means 1 mm on paper represents 5 mm of the object, and 5:1 is an enlargement.

First-angle projection places the object between the observer and the plane, so the view from the front appears below the front view in the layout; third-angle places the plane between observer and object, giving the view above the front view.

Line conventions: continuous thick for visible outlines, continuous thin for dimension and projection lines, dashed for hidden edges, chain thin for centre lines and pitch circles, and freehand for break lines.

Dimensioning rules: dimension lines are drawn parallel to the measured edge with arrowheads touching the extension lines; the unit (mm) is stated once in the title block and not repeated on each dimension.

A regular polygon of n sides has each exterior angle 360/n degrees and each interior angle (n-2) x 180/n degrees; the same relation locates vertices on a construction circle.

An ellipse is constructed by the concentric-circle or intersecting-arcs method; the major axis is the longest chord through both foci and the minor axis is perpendicular to it at the centre.

A helix development gives the true length of one turn as the square root of (pi x d)^2 + p^2, where d is the cylinder diameter and p the pitch.

Isometric projection uses axes at 30 degrees to the horizontal with true lengths multiplied by 0.816, whereas isometric drawing uses full lengths along the axes without that reduction.

Ohm's law: V = I x R; power P = V x I = I^2 R = V^2 / R, with V in volts, I in amperes, R in ohms, and P in watts.

Series circuits carry the same current through every element and add resistances (R = R1 + R2 + ...); parallel circuits share the same voltage and add conductances (1/R = 1/R1 + 1/R2 + ...).

Kirchhoff's laws: the current law states that the algebraic sum of currents at a node is zero; the voltage law states that the algebraic sum of voltages around a closed loop is zero.

For a sinusoidal supply, RMS value = peak / square root of 2, average value = 0.637 x peak, and form factor = RMS / average = 1.11 for a sine wave.

In a purely inductive circuit current lags voltage by 90 degrees; in a purely capacitive circuit current leads voltage by 90 degrees; impedance Z = square root of (R^2 + (XL - XC)^2).

Three-phase relations for a balanced star connection: line current equals phase current and line voltage equals square root of 3 times phase voltage; for delta, line voltage equals phase voltage and line current equals square root of 3 times phase current.

A diode conducts when forward biased above roughly 0.7 V for silicon and 0.3 V for germanium; a Zener diode is operated in reverse breakdown to regulate voltage.

Transformer relation: V1 / V2 = N1 / N2 = I2 / I1; a step-down transformer has fewer secondary turns and a higher secondary current for the same power.

Earthing provides a low-resistance path to earth so that a fault current trips the protective device; the earth wire is connected to the metal enclosure and never to a fuse or switch in the live line.

Plain carbon steel is classified by carbon content: low carbon (mild) up to about 0.3 percent C, medium carbon 0.3 to 0.6 percent C, and high carbon 0.6 to 1.4 percent C; hardness and strength rise with carbon while ductility and weldability fall.

Cast iron contains roughly 2 to 4 percent carbon; grey cast iron has flake graphite and good damping and machinability, while white cast iron has cementite and is hard and brittle.

Heat treatment terms: annealing softens and relieves stress by slow cooling, normalising refines grain structure by air cooling, hardening forms martensite by quenching, and tempering restores toughness after hardening.

Brass is an alloy of copper and zinc; bronze is mainly copper and tin; both resist corrosion and are used for bearings, bushes, and fittings.

Ferrous metals contain iron and are magnetic; non-ferrous metals such as aluminium, copper, and zinc are non-magnetic and generally lighter and more corrosion resistant.

Casting: sand casting uses a pattern, cope and drag moulding boxes, a sprue, runners, and risers; shrinkage allowance is added to the pattern, and draft allowance eases pattern withdrawal.

Welding processes: arc welding uses an electrode and a filler; gas welding uses an oxygen-acetylene flame with a neutral, oxidising, or carburising setting; brazing joins at a temperature above 450 degrees C but below the melting point of the parent metal.

Forging shapes metal by compressive force, hot or cold, improving grain flow and strength; rolling, extrusion, and drawing are other bulk forming processes.

Lathe operations include turning, facing, chamfering, knurling, and thread cutting; cutting speed in metres per minute equals pi x D x N / 1000, where D is diameter in mm and N is spindle speed in rpm.

Velocity ratio of a simple machine = distance moved by effort / distance moved by load; mechanical advantage = load / effort; efficiency = mechanical advantage / velocity ratio x 100 percent.

For a lever, load x load arm = effort x effort arm about the fulcrum; a first-class lever has the fulcrum between load and effort, a second-class lever has the load between them, and a third-class lever has the effort between them.

For a pulley system with n supporting rope segments, velocity ratio = n; a Weston differential pulley has velocity ratio 2D / (D - d) for pulley diameters D and d.

A screw jack with pitch p and handle radius R has velocity ratio 2 x pi x R / p; a worm and wheel has velocity ratio equal to the number of teeth on the wheel divided by the number of worm starts.

Gear trains: velocity ratio = product of teeth on driven gears / product of teeth on driving gears; for a simple train the ratio is N driven / N driver.

Belt drive slip reduces the speed ratio; velocity ratio for a belt drive is speed of driver / speed of driven, equal to the diameter of driven pulley / diameter of driver pulley for an open drive with no slip.

A four-stroke engine completes a cycle in two crankshaft revolutions: suction, compression, power, and exhaust strokes; a two-stroke engine completes a cycle in one revolution.

Bearing types: ball and roller bearings carry radial loads, thrust bearings carry axial loads, and plain bearings rely on an oil film; lubrication separates surfaces and reduces friction and wear.

Stress = force / cross-sectional area, strain = change in length / original length, and Young's modulus = stress / strain within the elastic limit.

Micrometer principle: least count = pitch of the screw / number of divisions on the thimble; for a 0.5 mm pitch screw with a 50-division thimble, least count = 0.01 mm.

Vernier calliper least count = value of one main-scale division / number of vernier divisions; for a 1 mm main division and 50 vernier divisions, least count = 0.02 mm.

Tool steel cutting tools are harder and more wear resistant than mild steel; high-speed steel retains hardness at higher temperatures and is used for drills and taps.

Tap drill size for a metric thread is approximately nominal diameter minus pitch; for an M10 x 1.5 thread the tapping drill is about 8.5 mm.

Preventive maintenance is scheduled by time or running hours before failure; breakdown maintenance is corrective work after failure; predictive maintenance uses measured condition such as vibration or oil analysis.

Bearing maintenance rules: correct lubricant grade and quantity, clean sealing, alignment of shaft and housing, and avoidance of over-tightening the belt or coupling.

Chain and belt drives are tensioned to the manufacturer's deflection value; an over-tight belt overloads bearings while a loose belt slips and wears.

Machine tool care: clean and oil slides and leadscrews daily, check coolant concentration, and never leave a chuck key in the chuck.

Accuracy is closeness to the true value; precision is repeatability of readings; a measurement can be precise but inaccurate when a systematic error is present.

Types of error: systematic (calibration, zero error), random (vibration, temperature fluctuation), and gross (misreading); systematic errors can be corrected by calibration.

Limits and fits: clearance fit always gives a positive gap, interference fit always gives an overlap, and transition fit may give either; tolerance is the difference between upper and lower limits.

Hole basis is preferred in industry because holes are made with fixed-size drills and reamers while shafts are ground to size; the hole is designated H in the hole-basis system.

Surface roughness Ra is the arithmetic mean deviation of the profile from the mean line, expressed in micrometres; lower Ra means a smoother surface.

Angular measurement: a sine bar gives sine of the angle = height of slip gauges / distance between rollers; a bevel protractor reads directly in degrees and minutes.

Quality control tools include the cause-and-effect (fishbone) diagram, Pareto chart, histogram, control chart, check sheet, scatter diagram, and flowchart.

Statistical process control uses upper and lower control limits at the mean plus or minus three standard deviations; points outside the limits indicate an assignable cause.

Inspection gauges: a Go gauge must pass over the maximum material condition and a No-Go gauge must not pass; the two limits are checked separately.

SI base units include metre (length), kilogram (mass), second (time), ampere (current), kelvin (temperature), mole (amount), and candela (luminous intensity).

Derived units follow from the definitions: force in newtons (kg m/s^2), pressure in pascals (N/m^2), work and energy in joules (N m), and power in watts (J/s).

Newton's second law F = m x a; weight W = m x g with g approximately 9.81 m/s^2; work = force x distance along the force; power = work / time.

Kinematics for uniform acceleration: v = u + at, s = ut + (1/2)at^2, and v^2 = u^2 + 2as.

Trigonometric ratios for a right triangle: sin = opposite / hypotenuse, cos = adjacent / hypotenuse, tan = opposite / adjacent; Pythagoras gives hypotenuse squared = sum of squares of the other two sides.

Area and volume formulas: circle area = pi r^2, circumference = 2 pi r, triangle area = (1/2) x base x height, cylinder volume = pi r^2 h, cone volume = (1/3) pi r^2 h.

Percentage, ratio, and proportion: percentage change = (new - old) / old x 100; for direct proportion the ratio of the two quantities stays constant.

Heat: sensible heat Q = m x c x temperature change; latent heat Q = m x L; the specific heat of water is about 4.18 kJ per kg per kelvin.

Statistics: mean = sum of values / number of values; median is the middle value when ordered; mode is the most frequent value; range = highest minus lowest.

Communication process elements: sender, message, encoding, channel, receiver, decoding, feedback, and noise; feedback confirms that the message was understood.

Types of communication: verbal, non-verbal, written, and visual; formal communication follows the organisation chart while informal communication spreads through social networks.

Active listening behaviours include maintaining eye contact, not interrupting, paraphrasing to confirm, and asking clarifying questions.

Resume essentials: personal details, career objective, education, technical skills, experience or projects, and references; a cover letter is tailored to the specific employer and role.

Interview preparation: research the organisation, prepare examples of work using the situation-task-action-result structure, and ask relevant questions at the end.

Teamwork roles: a team needs a leader, a planner, a doer, and a checker; conflict is resolved by focusing on the problem rather than the person.

Workplace ethics and rights: punctuality, honesty in reporting, respect for diversity and safety rules, and knowledge of the applicable labour law and grievance procedure.

Digital skills for employment: safe password practice, email etiquette with a clear subject line, and attaching files in common formats with a sensible file name.

Lifelong learning routes after HSC vocational study include apprenticeship, diploma, degree, and skill certification; each has its own entry requirement and duration.

A business plan sections: executive summary, product or service description, market analysis, marketing plan, operations plan, management team, financial plan, and risk assessment.

Market research methods: primary research collects new data through surveys, interviews, or observation; secondary research uses existing reports, census, and trade data.

Break-even quantity = fixed cost / (selling price per unit - variable cost per unit); contribution per unit is selling price minus variable cost.

Working capital = current assets - current liabilities; it measures short-term liquidity, and a positive value means current obligations can be met from current assets.

Sources of finance for a small enterprise: own savings, family loan, bank term loan, cash credit, government subsidy schemes, and equity from partners; each differs in cost and repayment obligation.

Forms of business organisation: sole proprietorship (single owner, unlimited liability), partnership, limited liability partnership, and private or public limited company.

A quotation or estimate states the scope, unit rates, taxes, delivery period, payment terms, and validity; an invoice records the goods supplied and the amount payable.

Customer communication: acknowledge the enquiry promptly, state what will be done and by when, confirm in writing, and follow up after delivery.

GST and statutory basics: a business registers for GST above the turnover threshold, must issue a tax invoice, and files periodic returns; records are retained for the statutory period.