Odisha CHSE +2 Vocational PDFM (RMPDFM) cheat sheet

PDFM/RMPDFM covers pattern making, foundry (moulding and casting) and fabrication/repair of metal furniture and structures.

Pattern allowance types: shrinkage (roughly 1-2% for cast iron, ~1.3% for steel, higher for aluminium), draft 1-3 degrees, machining 2-5 mm, and distortion allowance for U/V-shaped castings.

Shrinkage rule: shrinkage allowance = (shrinkage % x pattern dimension)/100; a shrink rule already incorporates the allowance so no separate addition is needed.

Draft is applied on vertical faces parallel to the draw direction; it is tapered so the pattern withdraws without tearing the sand.

Cores form internal cavities; core prints locate the core, chaplets support it, and vents allow gases to escape.

Sand moulding: green sand (moist), dry sand, loam, and CO2/sodium silicate moulds; green sand is cheapest and most common for small castings.

Gating system order: pouring basin, sprue, runner, gates, riser; a riser feeds shrinkage and must solidify after the casting.

Fabrication fundamentals: cutting, shearing, bending, rolling, and welding; sheet-metal bend allowance = angle in radians x (R + K x T).

Bench work sequence: marking, centre punching, hacksawing, chipping, filing, drilling, tapping, and finishing; file selection depends on cut coarseness and material.

Drilling speed rule: N = (1000 x V)/(pi x D), where V is cutting speed in m/min and D is drill diameter in mm.

Tap drill size for metric threads: minor diameter approximately equal to major diameter minus pitch (e.g., M10 x 1.5 uses a 8.5 mm tap drill).

Riveted lap joint: hole diameter is about 1.5 times rivet shank diameter for hot riveting; edge distance about 1.5 to 2 times diameter.

Casting procedure: place pattern, ram sand in layers, vent, withdraw pattern, cut gates and risers, close mould with core, pour at correct temperature, shake out and fettle.

Welding practice: clean the joint, set current per electrode diameter (about 30-40 A per mm of electrode core), maintain arc length roughly equal to electrode diameter, and chip slag between passes.

Sheet-metal layout uses a datum edge and dividers; bend lines are marked with a scriber and the bend allowance is added to the flat length.

Workshop housekeeping (5S) ends each session: tools returned to shadow boards, swarf cleared, and machines isolated.

First-angle projection (IS 696 / ISO-E) places the view of the object as seen from the front on the plane behind it; the top view goes below the front view.

Third-angle projection places the top view above the front view; Indian Standards practice is first-angle projection.

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

Scale = drawing length / actual length; representative fraction (RF) is written as 1:n for reducing scales.

Dimensioning rules: dimensions are placed on views showing true shape, not on hidden lines; each dimension is given once; arrowheads touch the extension lines.

Tolerances and fits are shown as limits (e.g., 25 +0.05/-0.00) or ISO symbols such as H7/g6, where H is a hole basis and g a shaft deviation.

Section views use hatching at 45 degrees; adjacent parts are hatched in opposite directions, and section lines are labelled A-A.

A welding symbol's reference line carries the arrow side (below) and other side (above) information; the tail holds process references such as 111 for arc welding.

Cast iron: about 2-4% carbon, brittle, good compressive strength, used for machine bases and pipe fittings; grey iron contains flake graphite.

Mild steel (low carbon, under 0.3% C) is ductile and weldable; medium carbon (0.3-0.6% C) is heat-treatable; high carbon (over 0.6% C) suits cutting tools.

Alloying elements: chromium improves corrosion resistance, nickel toughens, manganese improves hardenability, and silicon improves castability.

Heat treatment: annealing softens and relieves stress, normalising refines grain, hardening (quench) increases hardness, and tempering reduces brittleness after hardening.

Hacksaw blade pitch: 14 TPI for thick sections, 18 TPI general, 24 TPI for thin tube and sheet; at least three teeth must engage the work.

Safety: PPE includes goggles, helmet, gloves, safety shoes, ear plugs and apron; welding requires a filter shade of about 10-12 for arc currents above 100 A.

Fire classes: A solid, B flammable liquid, C gas, D metal; never use water on electrical or metal (D) fires.

Machine guards must be in place before starting; rotating chuck keys are removed immediately after use to prevent ejection injuries.

Least count of a vernier calliper = 1 main scale division - 1 vernier scale division; typical LC is 0.02 mm (50 divisions).

Micrometer least count = pitch of screw / number of divisions on thimble; a 0.5 mm pitch with 50 divisions gives 0.01 mm.

Vernier reading = main scale reading + (coinciding vernier division x least count).

Precision is repeatability of readings; accuracy is closeness to the true value. Random errors affect precision, systematic errors affect accuracy.

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

ISO 9001 covers quality management systems; ISO 14001 covers environmental management; IS 210 specifies grey iron castings grades.

Sampling inspection compares lot quality against an acceptance number (c) in an acceptance sampling plan; 100% inspection is used for critical safety parts.

Calibration compares an instrument against a standard traceable to national/international standards; gauge blocks are the reference for length.

Density = mass/volume; weight = mass x g (g = 9.81 m/s^2). Steel density is about 7850 kg/m^3, cast iron about 7200 kg/m^3, aluminium about 2700 kg/m^3.

Area of a circle = pi r^2 = (pi d^2)/4; circumference = pi d; pi = 22/7 approximately.

Volume of a cylinder = pi r^2 h; volume of a cone = (1/3) pi r^2 h; volume of a sphere = (4/3) pi r^3.

Pythagoras theorem: in a right triangle, hypotenuse^2 = base^2 + height^2, used for layout and diagonals.

Trigonometry for taper and angles: tan(theta) = opposite/adjacent; taper = (D - d)/L.

Stress = force/area (N/mm^2 = MPa); strain = change in length/original length; Young's modulus = stress/strain.

Ohm's law: V = I x R; power P = V x I = I^2 R; electrical energy in kWh = (watts x hours)/1000.

Temperature conversion: F = (9/5)C + 32; K = C + 273. Melting point of cast iron is about 1150-1200 C, mild steel about 1500 C.

A business plan sections: product/service, market analysis, production plan, marketing plan, organisation, and financial plan with break-even.

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

MSME classification in India uses investment and turnover limits; Udyam registration is the online portal for MSME registration.

GST registration is mandatory above the prescribed turnover threshold; invoices must carry GSTIN, HSN code and tax breakup.

Employability skills: punctuality, teamwork, problem solving, time management, and willingness to learn; interviews assess both technical and behavioural competence.

Communication process: sender, message, encoding, channel, receiver, decoding, feedback, and noise.

7 Cs of communication: clear, concise, concrete, correct, coherent, complete and courteous.

Safety and labour compliance: Employees' Provident Fund, ESI, and Factories Act provisions on working hours and safety apply to workshops.

CAD drawing uses layers, object snaps (endpoint, midpoint, centre, intersection), and ortho/polar tracking for accuracy.

Common CAD commands: LINE, CIRCLE, ARC, OFFSET, TRIM, EXTEND, MIRROR, ARRAY, DIMLINEAR, HATCH, and PLOT.

CAD file exchange formats: DWG (native), DXF (exchange), PDF (viewing/printing), and STL for 3D printing.

Spreadsheet formula begins with =; SUM, AVERAGE, IF and ROUND are used for costing, stock registers and wage calculations.

Absolute reference ($A$1) stays fixed when copied; relative reference (A1) changes; useful for GST and material rate tables.

Email etiquette: specific subject line, one topic per message, attachments named clearly, and reply within a reasonable time.

Digital safety: strong passwords, two-factor authentication, antivirus updates, and never share OTPs or bank credentials.

Government digital tools: Udyam portal, GeM (Government e-Marketplace), GST portal, and DigiLocker for document storage.

Foundry hazards: silica dust causes silicosis; use dust extraction, wet methods, and approved respirators.

Welding hazards: fumes (metal fume fever from zinc), UV arc eye (photokeratitis), and fire risk; use screens, local exhaust ventilation and eye protection.

Noise above 85 dB(A) for 8 hours requires hearing protection; noise is measured with a sound level meter.

Waste segregation: metal scrap, sand waste, oily waste, and e-waste are stored separately; foundry sand can be reclaimed and reused.

3R hierarchy: reduce, reuse, recycle; pollution control includes scrubbers, bag filters and effluent treatment before discharge.

Ethics at work: honesty in inspection records, no falsified test results, respect for safety rules, and reporting near-misses.

Ergonomics: correct lifting posture (bend knees, keep load close), work height adjustment, and periodic breaks reduce musculoskeletal injury.

First aid: burns are cooled with clean running water for at least 20 minutes; eye injuries are flushed with clean water and referred to a doctor.