Question 1

Oxy-acetylene welding — cylinder gas consumption for neutral flame In gas welding of mild steel with a neutral oxy-acetylene flame, if acetylene consumption from the cylinder is 10 litres, the approximate oxygen consumption from the cylinder will be:

Accepted Answer

Introduction / Context:Correct gas ratios are crucial in oxy-acetylene welding to achieve the desired flame chemistry. A neutral flame (balanced oxygen and acetylene) is typically used for mild steel to avoid oxidation or carburization. This question tests your grasp of gas consumption ratios at the torch.Given Data / Assumptions:Neutral flame is used for mild steel welding.Acetylene consumption from the cylinder is 10 litres.Flow rates are measured at the torch and reflect cylinder usage.Concept / Approach:A neutral flame requires approximately equal volumes (by flow rate) of oxygen and acetylene at the torch. Although total oxygen involved in combustion includes atmospheric oxygen, the oxygen delivered from the cylinder to form a neutral flame at the tip is roughly equal to the acetylene flow in typical practice.Step-by-Step Solution:Neutral flame condition → O2 (cylinder) ≈ C2H2 (cylinder).Given C2H2 = 10 litres → O2 ≈ 10 litres.Therefore, the best choice is 10 litre.Verification / Alternative check:Welding guides often recommend oxygen-to-acetylene flow ratios close to 1:1 for neutral flame on mild steel, with minor adjustments for tip size and joint geometry. Significant deviations indicate oxidizing or carburizing flames, which are not desired for general mild steel welding.Why Other Options Are Wrong:5 litre implies carburizing conditions; 15 or 20 litre implies oxidizing flame; 8 litre under-supplies oxygen and would not be neutral under standard settings.Common Pitfalls:Confusing total stoichiometric oxygen needs (including air entrainment in oxy-fuel cutting) with cylinder oxygen for welding; misreading regulator scales leading to incorrect flame chemistry.Final Answer:10 litre

Question 2

Sheet-metal operations — choosing the right term The operation of cutting a flat sheet to obtain the desired external shape (the cut-out is the product) is called:

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Introduction / Context:Many sheet-metal cutting operations look similar but differ in objective. Knowing whether the removed portion or the remaining sheet is the product determines the correct terminology and die design.Given Data / Assumptions:A flat sheet is cut to a required outer profile.The detached piece is the useful product (e.g., a washer blank).Conventional punch-and-die press tools are used.Concept / Approach:In blanking, the blank (cut-out) is the desired part, while the surrounding sheet becomes scrap. In punching/piercing, the hole is desired and the slug is scrap. Shearing is a straight-line cut separating sheets; nibbling removes small bits successively to create complex shapes.Step-by-Step Solution:Identify the product: the detached piece (blank) is required.Match with operation: blanking produces the blank as the product.Therefore select 'blanking'.Verification / Alternative check:Die sets for blanking have specific clearances and often require hold-downs/stripper plates to control the blank and ensure good edge quality; process sheets label the operation as blanking when the blank is the part.Why Other Options Are Wrong:Punching/piercing prioritize the hole; shearing is not profile blanking; nibbling is a progressive contouring method with different intent and finish.Common Pitfalls:Using 'punching' as a generic term for all press cuts; forgetting that cutting clearance and die wear affect edge rollover and burr, impacting blank dimensions.Final Answer:blanking

Question 3

Metal spinning — primary deformation mode During conventional metal spinning of circular blanks over a mandrel, the principal mode of deformation is:

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Introduction / Context:Metal spinning forms axisymmetric parts (lampshades, cookware, cones) by forcing a rotating sheet blank over a mandrel with a roller tool. Understanding how the sheet deforms helps in predicting thickness changes and avoiding tearing.Given Data / Assumptions:Conventional manual or CNC spinning of ductile sheet metals.Blank rotates on a lathe-type machine; roller tool applies local pressure.No intentional through-thickness compression like deep drawing with a punch/die pair.Concept / Approach:In spinning, the material near the tool undergoes localized bending as it conforms to the mandrel curvature and simultaneous in-plane stretching (tensile) causing some thinning. The overall deformation is a combination of bending and membrane stretching along the meridian of the part.Step-by-Step Solution:The tool forces material over changing curvature → bending occurs.Material flows along the surface lengthening in the meridional direction → stretching occurs.Therefore the correct description is 'bending and stretching'.Verification / Alternative check:Thickness measurements of spun parts typically show thinning at high curvature regions, corroborating stretching; spring-back after unloading confirms bending recovery effects.Why Other Options Are Wrong:Bending only ignores thinning; stretching only ignores curvature change; rolling/stretching without bending is unrealistic; pure compression does not describe spinning, which mainly uses tensile membrane forces.Common Pitfalls:Over-thinning due to excessive passes; wrinkling at flanges from insufficient support; tearing near the nose from high tensile strain without proper lubrication.Final Answer:bending and stretching

Question 4

TIG (GTAW) shielding gases In tungsten inert gas (TIG) arc welding, the weld zone is commonly shielded by:

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Introduction / Context:TIG (GTAW) welding requires an inert atmosphere around the tungsten electrode and molten pool to prevent oxidation and contamination. Selecting the proper shielding gas influences arc stability, heat input, and bead shape.Given Data / Assumptions:Process uses a non-consumable tungsten electrode.Shielding must be inert for clean, high-quality welds.Common base metals: aluminum, stainless steel, magnesium, titanium.Concept / Approach:Argon and helium are the standard inert gases for TIG. Argon offers easy arc starts and stable arcs; helium provides higher heat input and deeper penetration, useful for thick sections and high-conductivity metals. Mixtures of Ar-He tune performance. Active gases like CO2 or N2 are avoided in TIG because they destabilize the arc and contaminate the weld.Step-by-Step Solution:List acceptable inert gases: argon, helium, or their mixtures.Exclude active gases that would react with the weld pool (CO2, N2).Therefore, the shielding is provided by either argon or helium.Verification / Alternative check:Manufacturer application notes for GTAW torches specify argon or helium flow rates; gas mixtures like Ar-He are widely used for aluminum and copper alloys.Why Other Options Are Wrong:CO2 is typical for GMAW/MAG on steels, not TIG; nitrogen is reactive and causes porosity/embrittlement in many alloys during TIG.Common Pitfalls:Insufficient gas flow leading to porosity; drafts blowing away shielding; using incorrect gas for thick aluminum leading to lack of fusion.Final Answer:either (a) or (b)

Question 5

Cold working of metals — effect on size and structure Evaluate the statement: “Cold working distorts the grain structure and does not provide an appreciable reduction in size.”

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Introduction / Context:Cold working (deformation below the recrystallisation temperature) is central to sheet, bar, and wire production. It affects mechanical properties and geometry. This prompt asks whether cold working fails to reduce size appreciably.Given Data / Assumptions:Processes include cold rolling, cold drawing, swaging, and pressing.Materials are ductile metals at room temperature.No intermediate annealing unless specified.Concept / Approach:Cold working does two prominent things: it significantly reduces cross-section/changes thickness and it introduces strain hardening with elongated, distorted grains. Many industrial operations rely precisely on its ability to achieve large percentage reductions in thickness or area with good surface finish.Step-by-Step Solution:Consider cold rolling of sheet: thickness reductions of 30–70% (or staged with anneals) are common.Wire drawing can reduce diameter from, say, 10 mm to 2 mm through multiple draws.These are undeniably appreciable size reductions. Thus, the statement claiming 'no appreciable reduction' is incorrect.Verification / Alternative check:Engineering data sheets report percent cold work as the reduction of area or thickness; mechanical property changes (yield strength up, ductility down) correlate with these significant size reductions.Why Other Options Are Wrong:Any option endorsing the statement ignores commonplace reductions; limiting correctness to certain alloys is misleading because both ferrous and nonferrous metals undergo substantial reduction during cold work.Common Pitfalls:Confusing cold working with surface burnishing; assuming springback prevents thickness reduction; overlooking intermediate anneals that allow even larger cumulative reductions.Final Answer:Incorrect

Question 6

Hot piercing — typical applications Is hot piercing extensively used for making bolts and nuts in industrial practice?

Accepted Answer

Introduction / Context:Hot piercing is a bulk-deformation process where a solid billet is pierced to create a hollow, often as a precursor to seamless tubes (Mannesmann process). The question challenges a common misconception by asking whether hot piercing is widely used to produce bolts and nuts.Given Data / Assumptions:Bolts and nuts are standard fasteners.Typical manufacturing routes for fasteners include heading, thread rolling, machining, and forging.Hot piercing produces hollows/tubes rather than solid shanks and hexagonal nuts directly.Concept / Approach:Bolts are normally made by hot or cold heading (upsetting) to form the head on a solid rod or wire, followed by thread rolling or cutting. Nuts are made by hot or cold forging with later tapping for the internal thread. Piercing is not the primary method because bolts and nuts are not hollow products; piercing is aimed at hollow products such as seamless tubes, rings, or hollow forgings.Step-by-Step Solution:Identify what hot piercing creates: a central cavity in a hot billet.Compare to bolt/nut geometry: bolts require solid shank; nuts require through-hole made by punching/drilling/tapping after forging, not by tube-making methods.Therefore, hot piercing is not extensively used for bolts and nuts.Verification / Alternative check:Process plans for fastener manufacture (automotive, construction) show heading and thread rolling lines rather than piercing mills; piercing is found in tube and pipe mills.Why Other Options Are Wrong:'Yes' misstates common industry practice; material-specific options are red herrings since the geometry, not alloy, dictates process choice.Common Pitfalls:Confusing nut hole punching with large-scale hot piercing for tubes; assuming any operation that makes a hole qualifies as hot piercing in the metallurgical sense.Final Answer:No

Question 7

Hot Working of Metals — Choose the Correct Temperature Range In manufacturing metallurgy, “hot working” refers to plastic deformation performed relative to the material’s recrystallisation temperature. At which temperature range is hot working corre…

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Introduction / Context:Hot working is a fundamental concept in metal forming used in rolling mills, forging shops, and extrusion plants. Understanding the correct temperature window ensures desired grain refinement, eliminates work hardening, and reduces forming loads. This question checks whether you can correctly identify the operational temperature range for hot working relative to the metal’s recrystallisation temperature.Given Data / Assumptions:Recrystallisation temperature is the temperature at which new, strain-free grains nucleate and grow during or after deformation.During hot working, deformation and recrystallisation overlap (concurrent softening).Metals considered are typical engineering alloys like steel, aluminum, and copper alloys.Concept / Approach:When deformation is performed above the recrystallisation temperature, the metal continuously recrystallises as it is worked. This ongoing nucleation and growth of new grains counteracts work hardening, keeping flow stress relatively low and allowing large shape changes without cracking. This also improves ductility and refines microstructure if parameters are controlled.Step-by-Step Solution:Define target window: hot working must be done above the recrystallisation temperature of the alloy.Relate to forming load: above this temperature, flow stress is reduced, enabling large reductions.Relate to microstructure: continuous dynamic recrystallisation limits work hardening and can refine grains.Therefore, the correct selection is “above the recrystallisation temperature”.Verification / Alternative check:Practical evidence: hot rolling of steel typically occurs at temperatures well above the steel’s recrystallisation temperature, producing manageable loads and favorable microstructures.Why Other Options Are Wrong:At/below recrystallisation temperature: this is warm or cold working, where work hardening dominates and loads are higher.At any temperature: too imprecise; metallurgical behavior is temperature-dependent.Not applicable: contradicts standard definitions.Common Pitfalls:Confusing recrystallisation temperature with melting point; these are distinct and material-specific.Assuming “hot” simply means “high”—it must be high relative to recrystallisation, not an arbitrary number.Final Answer:above the recrystallisation temperature

Question 8

Foundry Practice — What Is a Swab Used For in Green Sand Moulding? During pattern withdrawal and mould finishing, which specific task is the swab intended to perform around edges and delicate features?

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Introduction / Context:Foundry hand tools are specialized for distinct tasks. Confusing them leads to mould damage or poor casting surfaces. A swab is commonly used during the delicate moment of pattern withdrawal to protect edges and prevent tearing of the green sand mould.Given Data / Assumptions:Moulding is being done with green (moist) sand in cope and drag.Patterns may have sharp edges, fillets, or fine details susceptible to crumbling.Tool kit includes swab, slick, trowel, riddle, gate cutter, and brush.Concept / Approach:The swab is a small, soft and wet applicator (often cotton or sponge on a stick). Its purpose is to add a controlled amount of moisture to the sand adjacent to the pattern edges. Slight moistening binds the sand locally, increasing cohesion and allowing cleaner draw without edge breakage.Step-by-Step Solution:Identify problem: edges crumble when pattern is withdrawn.Apply solution: dampen with the swab along the pattern perimeter and fillets.Effect: improved sand cohesion and reduced scabbing or edge tearing.Hence, the correct function is to moisten the sand around the edge before pattern removal.Verification / Alternative check:Standard foundry texts list swabbing as a pre-draw step to ensure a clean release.Why Other Options Are Wrong:Smoothing depressions is done with slicks/trowels.Cleaning sand is done with a riddle or screen; a swab does not sieve.Reinforcement of sand uses gaggers or chaplets, not swabs.Common Pitfalls:Over-wetting can collapse the mould surface; swab sparingly.Final Answer:moistening the sand around the edge before removing pattern

Question 9

Joining a Mild Steel Shank to a High-Speed Steel Drill — Select the Proper Resistance Welding Process In tool manufacture, what resistance welding method is commonly used to join a mild steel shank to a high-speed steel (HSS) drill body?

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Introduction / Context:Composite drills often consist of a high-speed steel (HSS) cutting portion joined to a tough mild steel shank to save cost and tailor properties. Selecting the appropriate resistance welding process ensures a sound joint with minimal defects and good alignment for subsequent grinding.Given Data / Assumptions:Dissimilar steels: HSS (high alloy) and mild steel.Axial bar-to-bar joining geometry (coaxial rods).Need for high-quality bond along the full cross-section with minimal inclusions.Concept / Approach:Flash butt welding uses controlled arcing (flashing) at abutting faces to uniformly heat and expel surface oxides. Once adequate plasticity and cleanliness are achieved, a strong upset force forges the joint. This method is well-suited to axial bar joints, managing differences in composition and thermal properties between HSS and mild steel.Step-by-Step Solution:Prepare bars with square faces and alignment.Flash: bring ends together under low force to create arcing, heating, and expelling oxides.Upset: apply high axial force to forge the joint and consolidate the interface.Cool under control to reduce residual stress and preserve HSS properties.Verification / Alternative check:Industrial practice routinely uses flash butt welding for drills, reamers, and similar tools with dissimilar shanks.Why Other Options Are Wrong:Spot/seam welding suit sheet products, not coaxial bars.Upset butt welding lacks the flashing stage, making oxide removal less effective for HSS-MS combinations.Projection welding is for localized nuggets under raised features, not full-section bar joints.Common Pitfalls:Overheating can degrade HSS temper; precise control of flashing and cooling is essential.Final Answer:flash butt welding

Question 10

Safety Identification — Standard Cylinder Color for Acetylene (Shop Practice) In workshop gas handling under typical Indian/ISO color practice, acetylene cylinders are usually painted which color for quick identification?

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Introduction / Context:Correct gas cylinder color identification is a critical safety practice in welding and cutting shops. Misidentification can lead to dangerous connections or incorrect regulator use. Acetylene, being highly flammable and stored in porous mass with solvent, has a standard color for its cylinders in many regions including India.Given Data / Assumptions:Conventional workshop color codes applied (Indian/ISO practice).Cylinders are visually identified before attaching regulators and hoses.Focus is on acetylene used with oxygen for oxy-fuel welding/cutting.Concept / Approach:Color codes provide redundant safety cues beyond label text. Under common practice, acetylene cylinders are maroon, oxygen cylinders are black (or sometimes white/black depending on local standards), and inert gases have their own codes. Trainees must internalize these visuals to prevent cross-connection.Step-by-Step Solution:Identify the target gas: acetylene for oxy-fuel welding.Recall standard shop code: acetylene → maroon body.Therefore, the correct choice is “maroon colour”.Verification / Alternative check:Cross-verify with institutional safety charts or supplier documentation in your facility; maroon is consistently specified for acetylene in Indian practice.Why Other Options Are Wrong:Black/white/yellow/green correspond to other gases or regional variants; not the standard acetylene code in the stated context.Common Pitfalls:Relying solely on color without reading labels; always confirm contents before use.Final Answer:maroon colour

Question 11

Pattern Materials — Which Allowance Is Typically Smaller for Metal Patterns than for Wooden Patterns? Considering surface finish and strength of pattern materials, which allowance is generally required to be less when using metal patterns instead of…

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Introduction / Context:Pattern material affects dimensional allowances because of surface finish, strength, and wear resistance. Wooden patterns are more flexible and rougher, while metal patterns (aluminum, brass) are stronger, dimensionally stable, and smoother. This influences how much taper (draft) is needed for clean withdrawal from the sand mould.Given Data / Assumptions:Comparison is for identical casting design, same moulding sand and process.Metal patterns are stiffer and maintain sharper edges.Allowance definitions: shrinkage (compensate metal contraction), machining (post-cast material removal), draft (taper for pattern draw), distortion (for warpage tendencies).Concept / Approach:Smoother surfaces and precise geometry of metal patterns reduce friction against sand during draw, allowing smaller draft angles while still ensuring clean release. Shrinkage and machining allowances depend on the casting alloy and finish requirements, not on pattern material. Distortion allowance relates to casting behavior under solidification, again independent of pattern material selection.Step-by-Step Solution:Identify which allowance depends on pattern surface and rigidity: draft.Note that shrinkage and machining are casting-alloy/finish dependent, not pattern-material dependent.Conclude: metal patterns require less draft than wooden patterns for the same mould.Verification / Alternative check:Foundry handbooks list recommended draft values; metal patterns consistently allow smaller draft angles owing to reduced abrasion and better finish.Why Other Options Are Wrong:Shrinkage: set by metal being cast (e.g., grey iron ~10 mm/m, steel ~20 mm/m).Machining: determined by surface finish tolerance of final part, not the pattern material.Distortion: influenced by geometry and alloy solidification behavior.Common Pitfalls:Confusing rapping/shake allowance with draft; rapping can slightly enlarge the cavity but is a separate practice.Final Answer:draft allowance

Question 12

Master Pattern Allowance — Wooden Master for Casting an Aluminium Pattern (to be Used Later for Grey Iron) An aluminium pattern is to be produced by casting it from a wooden master pattern. What shrinkage allowance should be provided on the wooden m…

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Introduction / Context:Patternmaking often uses a wooden master to cast a durable aluminium pattern. The allowance to be applied on the wooden master must correspond to the shrinkage of the aluminium pattern casting itself, not the final grey iron casting that will later be produced using the aluminium pattern.Given Data / Assumptions:Step 1: Wooden master → Aluminium pattern (casting process).Step 2: Aluminium pattern → Grey iron castings (later production use).Typical linear shrinkage values (approximate): aluminium ~13–16 mm/m, grey iron ~10 mm/m, steel ~20 mm/m, magnesium ~26 mm/m.Concept / Approach:The allowance added to the wooden master must offset the contraction that occurs when molten aluminium solidifies to form the aluminium pattern. Therefore, choose the value appropriate for aluminium. Many shop tables round to convenient values; 16 mm/m is a commonly adopted allowance for aluminium patterns to ensure the produced aluminium pattern meets nominal dimensions for later service.Step-by-Step Solution:Identify target: compensate shrinkage of the aluminium pattern casting (not grey iron).Consult typical allowances: aluminium ≈ 13–16 mm/m.Among choices, the correct practical value is 16 mm/m.Therefore, select 16 mm/m for the wooden master.Verification / Alternative check:Patternmaker charts often specify aluminium at ~1.3–1.6%; selecting the higher standard value ensures safe tolerancing in production.Why Other Options Are Wrong:10 mm/m suits grey iron, which is not the metal of the pattern casting step.20 mm/m is typical for steel and would oversize the aluminium pattern.26 mm/m corresponds to magnesium alloys, not aluminium.6 mm/m is too small for aluminium and would under-compensate shrinkage.Common Pitfalls:Confusing allowances for the pattern metal with those for the final casting alloy.Final Answer:16 mm/m

Question 13

Moulding Machines — Characteristic of a Diaphragm Moulding Machine What sand hardness/packing profile is produced in a flask when using a diaphragm moulding machine with membrane pressure compaction?

Accepted Answer

Introduction / Context:Moulding machines differ in how they compact sand. Jolt, squeeze, jolt-squeeze, sand-slinger, and diaphragm (membrane) machines each create distinctive hardness profiles. Knowing these profiles helps you pick the right machine for dimensional accuracy and surface finish.Given Data / Assumptions:Diaphragm machine uses air pressure acting through a flexible membrane to compact sand.Pressure distribution is broad and nearly uniform compared with localized tamping.Objective is consistent sand hardness with minimal gradients.Concept / Approach:With membrane pressure, the applied load spreads over the mould area, reducing the extreme hardness gradients typical of jolt-only (harder near the pattern plate) or squeeze-only (harder near the squeeze head). The result is a comparatively uniform hardness/packing throughout the depth of the mould, which improves stability and reduces distortion.Step-by-Step Solution:Identify compaction mechanism: a flexible diaphragm distributes pressure uniformly.Predict effect: fewer localized peaks; more uniform sand density.Therefore, the correct description is “give uniform sand hardness throughout the mould”.Verification / Alternative check:Process comparisons in foundry texts depict diaphragm packing curves as flatter than jolt or squeeze methods.Why Other Options Are Wrong:Options A and B describe gradients characteristic of jolt or squeeze processes, not diaphragm.Option C is vague; option D explicitly states uniform hardness and matches diaphragm behavior.Common Pitfalls:Assuming all machine moulding gives similar hardness; mechanism matters.Final Answer:give uniform sand hardness throughout the mould

Question 14

Metrology — Define “Tolerance” in Limits and Fits For a given dimension, what do we call the difference between the specified upper limit size and lower limit size?

Accepted Answer

Introduction / Context:Limits and fits ensure interchangeability by controlling size variations. Designers and inspectors must use precise terms—mixing up tolerance, allowance, and size definitions leads to errors in drawings and inspection reports.Given Data / Assumptions:Dimension has an upper limit and a lower limit on an engineering drawing.Measurements follow standard ISO/ANSI conventions.We are defining a term, not calculating a value.Concept / Approach:Tolerance is the permitted size variation, defined as upper limit minus lower limit. Allowance, in contrast, is the intentional difference between mating parts’ basic sizes (e.g., minimum clearance or maximum interference). Nominal or basic size is the reference from which limits are derived; actual size is what is measured on the part produced.Step-by-Step Solution:Upper limit − Lower limit = permitted variation.By definition, this is called “tolerance”.Therefore, select option “tolerance”.Verification / Alternative check:Standards glossaries (ISO 286) define tolerance exactly as the difference between the limits of size.Why Other Options Are Wrong:Nominal/basic size: reference dimensions, not a range.Actual size: the measured value on the finished part.Allowance: intended fit difference between mating components, not a single-part variation.Common Pitfalls:Interchanging allowance and tolerance; one is for mating parts, the other for permissible size variation.Final Answer:tolerance

Question 15

Casting Methods — Identify the Process: Gravity Filling of a Metallic Mould When molten metal is poured by gravity into a reusable metallic mould (without external pressure), which casting method is being used?

Accepted Answer

Introduction / Context:Understanding the differences among gravity permanent mould casting, pressure die casting, slush casting, and centrifugal casting helps in selecting the right process for production rate, surface finish, and mechanical properties.Given Data / Assumptions:Mould is metallic and reusable (e.g., cast iron or steel mould).Filling occurs by gravity, not by high pressure or rotation.No skin-only removal step is implied.Concept / Approach:Permanent mould casting uses metal moulds and gravity to fill the cavity. Die casting uses high pressure (hot or cold chamber). Slush casting allows the skin to solidify and the core to be poured out to create hollow castings. Centrifugal casting relies on rotation to force metal against the mould walls.Step-by-Step Solution:Check mould type: metallic and reusable → permanent mould family.Check filling mechanism: gravity only → permanent mould casting (not die casting).Therefore, choose “permanent mould casting method”.Verification / Alternative check:Process charts classify gravity permanent mould separately from pressure die casting.Why Other Options Are Wrong:Die casting uses pressure injection.Slush casting is a variant for hollow skins, not general gravity filling for solids.Centrifugal casting requires rotation; not present here.Continuous casting is a different continuous process involving a water-cooled mold and withdrawal system.Common Pitfalls:Assuming any metal mould implies die casting; pressure application distinguishes die casting from gravity permanent mould.Final Answer:permanent mould casting method

Question 16

Filing Techniques — Name the Method When the File Is Moved To and Fro Across the Work In bench fitting, what is the common term for the technique where the file is pushed forward and pulled back repeatedly over the job surface (across the width)?

Accepted Answer

Introduction / Context:Filing operations are basic to bench work. Recognizing filing methods improves productivity and surface quality. Two commonly taught techniques are cross filing and draw filing, each suited to different finish and flatness requirements.Given Data / Assumptions:A standard single- or double-cut hand file is used with a handle.Operator moves the file forward and back in strokes over the surface.Objective: material removal and general flatness, not ultra-fine finishing.Concept / Approach:Cross filing refers to pushing the file across the work with successive normal strokes and often using a criss-cross pattern to average out high spots. Draw filing, by contrast, involves holding the file across the work and drawing it lengthwise toward oneself to create a finer surface finish with shallow cutting action. The question’s “to and fro” strokes describe cross filing practice, not the lateral draw technique.Step-by-Step Solution:Identify motion: repeated forward and backward strokes along the file’s length.Relate to method: that is characteristic of cross filing for bulk removal and shaping.Therefore, the correct choice is “cross filing”.Verification / Alternative check:Workshop manuals classify draw filing as lateral strokes with the file held sideways; not the same as the to-and-fro strokes described.Why Other Options Are Wrong:Draw filing uses side-to-side motion for smooth finish.“Pull and push filing” is an informal phrase and not the standard term.Lathe filing is done on rotating work, not bench work.Common Pitfalls:Using excessive pressure on the return stroke; lift slightly on the return to prevent dulling and chatter.Final Answer:cross filing

Question 17

Rolling mills — configuration of a two-high stand In metal rolling practice, a two-high rolling mill uses two work rolls mounted one above the other. For such a mill, the two rolls are typically of what relative size?

Accepted Answer

Introduction / Context:Rolling mills reduce thickness by passing metal stock between rotating rolls. A two-high rolling mill is the simplest stand arrangement and is commonly used in primary breakdown and in reversing mills. Knowing the relative size of the two rolls helps learners understand load sharing, deflection, and bite conditions.Given Data / Assumptions:Configuration: two rolls in a single stand, one above the other.Objective: identify the typical relative size used in industry teaching and exams.Consider standard, non-specialized hot or cold rolling of strips/plates/blooms.Concept / Approach:In a conventional two-high mill, the two work rolls are made with the same nominal diameter and face (barrel) length so that contact geometry, flattening, torque, and power transmission are symmetrical. Equal size simplifies bearing, chock, and drive design and allows reversing operation without changing contact conditions.Step-by-Step Solution:Recall that two-high stands typically use identical work rolls to maintain symmetry.Recognize that equal roll size provides equal surface speed and bite angle during reversing passes.Conclude that “equal” is the standard answer.Verification / Alternative check:Shop layouts and textbooks show two-high reversing stands with matched roll diameters. Any crown (barrel camber) is a subtle profile modification, not a diameter mismatch between rolls.Why Other Options Are Wrong:Different or stepped rolls: used in some special mills (e.g., cluster/Sendzimir) but not in basic two-high stands.Different barrel length: would limit product width and create edge defects.Crowned upper/flat lower only: crown is applied to both rolls to counter roll bending.Common Pitfalls:Confusing two-high with four-high or cluster mills where backup rolls differ from work rolls. Also, mistaking crown (a slight barrel convexity) for different roll diameters.Final Answer:equal

Question 18

Oxy-fuel cutting of steel — when does the cut edge harden? During oxygen cutting (oxy-fuel), the cut edge of a steel plate can harden due to rapid heating and quenching. At approximately what carbon content does this edge-hardening become significan…

Accepted Answer

Introduction / Context:Oxy-fuel cutting works by preheating steel to ignition temperature and then oxidizing iron with a jet of oxygen. The heat-affected zone (HAZ) experiences rapid thermal cycles. For certain carbon levels, the HAZ can transform to hard martensitic structures upon self-quenching, creating a brittle edge that is harder to machine or weld.Given Data / Assumptions:Process: oxy-fuel cutting of plain carbon steels.Cooling: relatively rapid due to surrounding cold metal acting as a heat sink.Question: identify the approximate carbon content where hardening risk rises.Concept / Approach:Hardenability increases with carbon content. Steels above about 0.3% C have enough carbon to form significant martensite if heated above the austenitizing range and quenched quickly. In oxy-cutting, the thin HAZ can cool fast enough to produce martensite for C > ~0.3%, giving a hard rim that may require grinding or tempering.Step-by-Step Solution:Recognize that the HAZ is heated to austenite during cutting.Note that rapid cooling favors martensite if carbon is adequate.Select the threshold “more than 0.3 percent” as the practical guideline.Verification / Alternative check:Shop practice flags oxy-cut edges on medium/high-carbon steels for post-heat or tempering; low-carbon steels (Why Other Options Are Wrong:Less than 0.1% or 0.3%: carbon too low for significant martensite formation.Anywhere 0.1–1% regardless: cooling rate and composition both matter; not all compositions harden the same.Only above 1.2%: hardening begins far below this level.Common Pitfalls:Assuming all oxy-cut edges are equally hard; ignoring preheat/slow-cooling practices that reduce hardening, especially before welding.Final Answer:more than 0.3 percent

Question 19

Core making in foundry — which moulding sand is preferred for cores? In sand casting, separate core assemblies are used to form internal cavities. Which type of sand mix is commonly used specifically for making cores?

Accepted Answer

Introduction / Context:Cores are inserts placed inside the mould cavity to create internal passages or undercuts in a casting. Unlike the mould, which may be made in green sand, cores must possess adequate strength at handling and at pouring temperature, good collapsibility, and surface finish suited to the internal features.Given Data / Assumptions:Cores are baked (or chemically hardened) before use.Binder system should provide hot strength and easy shake-out.Question seeks the traditional sand type referenced in many syllabi.Concept / Approach:“Oil sand” (core sand) is silica sand bonded with drying oils (linseed, etc.) and additives; it is rammed into core boxes and baked to develop strength. While modern shops also use CO₂-sodium silicate or resin-bonded sands, the conventional textbook answer associates cores with oil-bonded core sand distinct from green sand used for moulds.Step-by-Step Solution:Identify that cores require different properties from mould faces.Recall traditional practice: oil-bonded core sand is baked to gain strength.Select “oil sand” as the standard choice for cores.Verification / Alternative check:Foundry manuals list oil-bonded core sands and shell cores as common core-making systems, contrasted with green sand moulds.Why Other Options Are Wrong:Green sand: primarily for mould cavity; insufficient hot strength for most cores.Dry sand/loam sand: used for large moulds or special shapes, not the standard core mix.CO₂ sand only: modern method, but the question aims at the classic core material.Common Pitfalls:Assuming the same sand mix serves both mould and core; neglecting core venting and collapsibility.Final Answer:oil sand

Question 20

Forging terminology — operation that reduces cross-section and increases length In smithy/forging practice, which operation specifically decreases the cross-section of a bar while increasing its length?

Accepted Answer

Introduction / Context:Forging operations reshape hot metal through compressive deformation. Each named operation indicates a characteristic change in geometry. Correct identification ensures proper tool selection, energy estimation, and process planning.Given Data / Assumptions:Workpiece: bar stock heated to forging temperature.Objective: reduce cross-section, lengthen the bar.Manual or power hammer may be used with flatters/fullers.Concept / Approach:“Drawing down” (also called drawing out) elongates the work while decreasing its section by hammering or rolling. In contrast, “upsetting” shortens length while increasing section, “spinning” is a sheet-metal process on a lathe, and “peening” is a surface working/finishing step that redistributes metal locally without the systematic elongation associated with drawing down.Step-by-Step Solution:Match the required geometric change (smaller cross-section, greater length) to the correct term.Recognize that drawing down employs longitudinal flow induced by compressive blows.Select “drawing down.”Verification / Alternative check:Textbook forging sequences show drawing operations before sizing, using fullers to localize deformation then planishing to final dimensions.Why Other Options Are Wrong:Upsetting: reverse of the required change.Spinning: sheet forming, not bar forging.Peening/heading: finishing or head formation, not general elongation.Common Pitfalls:Confusing drawing down with wire drawing (a different die-drawing process) or with extrusion; mixing up upsetting vs. drawing terminology.Final Answer:drawing down

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