Question 1

Sheet-metal operations — term for longitudinal straight cutting What is the correct name for the operation in which a sheet or strip is cut in a straight line along its length to produce narrower strips?

Accepted Answer

Introduction / Context: Press-shop terminology distinguishes between different shearing and forming actions. Using the right term helps avoid ambiguity in process planning and tooling design. Given Data / Assumptions: Straight, longitudinal cut along the length of a coil or sheet. Objective is to divide a wide strip into multiple narrow strips. No deliberate bending or forming during the cut. Concept / Approach: “Slitting” is the longitudinal shearing of sheet or strip to reduce width. It is done on a slitting line or with rotary slitter knives. This differs from “notching” (removing a piece from an edge), “lancing” (partial cut followed by a bend), “plunging” (non-standard term in this context), and “forming” (plastic deformation without material removal). Step-by-Step Solution: Identify action: straight cut along length.Map action to standard term: slitting.Select “slitting”. Verification / Alternative check: Coil processing lines are commonly called “slitting lines”, confirming the accepted terminology. Why Other Options Are Wrong: Notching: local removal at an edge or corner. Lancing: partial cut plus bend to form tabs/louvers. Forming: changes shape without cutting. Plunging: not a standard press term for longitudinal shearing. Common Pitfalls: Confusing slitting with “shearing” generally; shearing is the broader category, while slitting is specifically longitudinal. Final Answer: slitting

Question 2

Brazing practice — commonly used flux Which flux is most commonly used in brazing to dissolve surface oxides and promote wetting of the filler metal?

Accepted Answer

Introduction / Context: Brazing joins metals using a filler that melts above soldering temperatures but below the base metal melting point. Flux selection is crucial because clean, oxide-free surfaces are required for good wetting and capillary action. Given Data / Assumptions: General-purpose brazing on steels and copper alloys. Conventional torch or furnace brazing environment. Goal is reliable oxide removal and protection during heating. Concept / Approach: Borax (sodium tetraborate) and borax-based mixtures are the standard fluxes for brazing. They dissolve metal oxides, protect the surfaces from further oxidation at elevated temperatures, and improve flow of the filler. Zinc chloride and ammonium chloride are more common in soft soldering as “killed spirits” or active fluxes. Rosin in alcohol is a mild, non-corrosive soldering flux for electronics, not for high-temperature brazing. Step-by-Step Solution: Identify the joining method: brazing (high temperature, capillary flow).Match flux chemistry to temperature/oxides: borax-based fluxes withstand brazing temperatures and dissolve oxides.Select “borax”. Verification / Alternative check: Materials handbooks and filler metal datasheets list borax/boric acid blends as the most widely used brazing fluxes. Why Other Options Are Wrong: Zinc chloride / Ammonium chloride: primarily soldering fluxes; too active/corrosive for many brazing applications. Rosin with alcohol: for electronics soldering at low temperatures. Caustic soda: not a brazing flux. Common Pitfalls: Using soldering fluxes in brazing leads to residues and poor joint wetting at high temperatures. Final Answer: borax

Question 3

Chisels — application of a diamond-pointed chisel A diamond-pointed chisel is primarily intended for which type of work during fitting or chipping operations?

Accepted Answer

Introduction / Context: Hand chisels are shaped to suit specific tasks. Selecting the correct chisel improves finish and reduces effort. The diamond-pointed chisel has a unique tip geometry that directs cutting forces into a narrow V-shaped path. Given Data / Assumptions: Standard chisel set: flat, cross-cut, round-nose, and diamond-pointed. Work materials: mild steel or cast iron in fitting shop practice. Objective: produce or clean internal corners or V-grooves. Concept / Approach: The diamond-pointed chisel has a pyramidal point ground to create two cutting edges meeting at a central ridge. This shape is ideal for V-grooves, sharp corners, and channels where a flat or cross-cut chisel cannot access. For keyways and straight grooves, a cape (cross-cut) chisel is preferred; for flat surfaces, a flat chisel is used; for semicircular channels, a round-nose chisel is appropriate. Step-by-Step Solution: Match chisel geometry to task geometry.Diamond-pointed tip naturally creates V-shaped cuts.Select “V-shaped grooves”. Verification / Alternative check: Workshop manuals depict the diamond-point chisel cleaning corners and producing V-shaped notches. Why Other Options Are Wrong: Flat surfaces: require a flat chisel. Grooves / keyways: generally require a cape chisel. Round holes: drills/reamers or round-nose chisel for channels, not the diamond point. Common Pitfalls: Using a diamond-point for wide material removal leads to chatter and poor surface finish. It is a specialty tool for corners and V-grooves. Final Answer: V-shaped grooves

Question 4

Resistance welding — typical electrode pressure range In electric resistance welding (e.g., spot welding) of steel sheets, what is a typical range of applied electrode pressure required to form a sound nugget?

Accepted Answer

Introduction / Context: In resistance spot welding, quality depends on three primary parameters: current, time, and pressure (force). Proper electrode pressure ensures intimate contact, controls current density, and forges the molten nugget during solidification. Given Data / Assumptions: Mild steel or similar sheet metals of typical automotive thicknesses. Standard domed copper alloy electrodes. Industrial equipment with pneumatic or servo guns. Concept / Approach: Electrode pressure must be high enough to break surface films, maintain contact, and contain the molten pool, but not so high that it expels molten metal or starves the joint of heat. For common gauges, forces correspond to pressures around 5 to 10 MPa when referenced to electrode face area. Lower than 5 MPa risks arcing and expulsion; much higher pressures are reserved for special cases or thick stacks. Step-by-Step Solution: Relate typical electrode force to face area to estimate pressure.Consult standard practice: automotive schedules cluster around 5–10 MPa.Select “5 to 10 MPa”. Verification / Alternative check: Welding procedure specifications and textbooks tabulate recommended forces that, when converted to pressure, fall within this range for usual electrode diameters. Why Other Options Are Wrong: 1 to 5 MPa: often insufficient; unstable contact and splash risk. 10 to 25 MPa or 25 to 55 MPa: too high for standard thin sheets; may cause indentation and expulsion. 0.1 to 0.5 MPa: far too low to maintain contact. Common Pitfalls: Confusing force (N) with pressure (MPa). Always normalise by electrode face area when comparing setups. Final Answer: 5 to 10 MPa

Question 5

Riveted and welded joints — thickness range suited to lap joints In fabrication practice, lap joints are generally preferred for relatively thin plates. For which thickness range are lap joints typically employed?

Accepted Answer

Introduction / Context: Joints in sheet and plate fabrication are selected based on thickness, load path, ease of assembly, and inspection requirements. Lap joints overlap members and are common in thin-gauge work for both riveting and welding (especially resistance spot welding). Given Data / Assumptions: General fabrication context (sheet-metal, light structures). Focus on practical workshop guidance rather than a strict code clause. Thinner plates permit easy overlap without excessive step height. Concept / Approach: Lap joints avoid the need for edge preparation and maintain alignment easily on thin sheets. As thickness increases, the offset created by the overlap becomes less acceptable, stress contours worsen, and butt joints with proper edge preparation are preferred. For very thin sheets (below roughly 3 mm), lap joints are convenient and economical. Step-by-Step Solution: Relate joint type to plate thickness.Recognise that thin sheets favour lap joints for ease and speed.Select “less than 3 mm”. Verification / Alternative check: Shop standards for sheet-metal ducts, enclosures, and automotive body panels overwhelmingly use lap configurations in these thin thicknesses. Why Other Options Are Wrong: 5 to 10 mm / 12.5 mm / above 25 mm: butt joints with full penetration or multi-pass welds are typically specified; lap joints become bulky and create stress raisers. Exactly 20 mm: not representative of common lap-joint usage. Common Pitfalls: Confusing riveted boiler joints (historical) with modern sheet-metal practice; the typical classroom guideline emphasises lap joints for thin plates. Final Answer: less than 3 mm

Question 6

Files — grade identification by teeth count If a file has 20 teeth within a length of 25 mm (approximately 20 teeth per inch), what is this file commonly called with respect to its cut grade?

Accepted Answer

Introduction / Context: Files are graded by coarseness based on the number of teeth per unit length. Coarser files remove material faster but leave a rougher finish; finer files provide better surface finish with slower stock removal. Recognising the grade from a tooth count helps in correct tool selection. Given Data / Assumptions: Teeth count is 20 within 25 mm (≈ 20 TPI). Classification follows common workshop practice where fewer teeth per inch indicate a coarser (rough) cut. Single-cut or double-cut details do not alter the grade naming here. Concept / Approach: As the number of teeth per inch increases, the file becomes finer. Typical qualitative order (from coarse to fine) is: rough > bastard > second cut > smooth > dead-smooth. Around 20 teeth per inch falls in the coarse range, corresponding to a “rough” file in many workshop charts. By contrast, smooth and dead-smooth files would exhibit significantly higher tooth densities. Step-by-Step Solution: Interpret the given count: 20 teeth in 25 mm ≈ 20 TPI.Compare to qualitative ranges: low TPI = coarse.Select the matching grade: “rough file”. Verification / Alternative check: Reference tables in fitting textbooks show rough files with the lowest tooth densities, often near this value, with successive grades having increasing TPI. Why Other Options Are Wrong: Bastard / Second cut: intermediate tooth densities, finer than rough. Smooth / Dead-smooth: substantially higher tooth counts for finishing. Common Pitfalls: Confusing TPI with teeth per centimetre; ensure consistent units when comparing to charts. Final Answer: rough file

Question 7

Workshop metrology and hand tools — hacksaw blade length definition: In hand fitting practice, the specified length of a hacksaw blade is measured between which features on the blade?

Accepted Answer

Introduction / Context: Knowing how a hacksaw blade's length is defined is essential for correct replacement and for ensuring the frame can tension the blade properly. Toolroom and workshop standards specify the reference points used to measure blade length so that frames, pins, and hole spacing are compatible across manufacturers. Given Data / Assumptions: Standard hand hacksaw blades used in fitting and fabrication. Blade has two mounting holes that fit on frame pins. We are identifying the correct metrological definition of blade length. Concept / Approach: Interchangeability requires a consistent datum. The only datum that is invariant to hole diameter and edge chamfers is the centre of each hole. Therefore, standards define blade length as the distance between the centres of the two mounting holes. References to outer or inner edges can vary with hole size and countersink, leading to mismatch and poor tensioning. Step-by-Step Solution: Identify fixed datums on the blade: the two circular holes for frame pins.Choose the feature whose position is independent of hole diameter: the centre of each hole.Therefore, blade length = distance between the centres of the two pin holes.Other edge-based measurements change with hole diameter or wear and are not standard. Verification / Alternative check: Check a blade and frame: if the hole-centre spacing matches the frame's adjustable distance, the blade tensions correctly; measuring to hole edges yields inconsistent fit. Why Other Options Are Wrong: Outside or inside edges depend on hole diameter and chamfer, so lengths won't be consistent. Tip-to-tip toothed length ignores the mounting geometry entirely. Frame window length varies with frame design and tension setting; it is not a blade standard. Common Pitfalls: Ordering blades by overall metal strip length instead of hole-centre spacing; mixing junior (150 mm) and full-size (300 mm) blades due to misreading specifications; assuming all frames can compensate for several millimetres of error in length—many cannot. Final Answer: the centres of the two pin holes

Question 8

Gas welding safety — storage of acetylene: In which form is acetylene safely stored inside its cylinder for oxy–acetylene welding and cutting?

Accepted Answer

Introduction / Context: Acetylene is a highly energetic fuel gas used in oxy–fuel welding and cutting. Safe storage is critical because free acetylene becomes unstable above modest pressures and can decompose explosively. Understanding the correct storage method is a core safety competency for welding operations. Given Data / Assumptions: Industrial acetylene cylinders used with regulators and flashback arrestors. Goal is safe, stable storage under usable pressure. No external refrigeration is used in common shop practice. Concept / Approach: Acetylene is stored by dissolving it in a solvent (typically acetone or dimethylformamide) contained in a porous mass inside the cylinder. This solution storage greatly increases the safe pressure range and suppresses decomposition. The cylinder is used upright so the gas exits above the solvent; excessive withdrawal rates risk solvent carryover, which must be avoided. Step-by-Step Solution: Recognise acetylene instability at pressure when free (gaseous).Adopt solution storage: porous filler + acetone dissolve acetylene safely.Use upright cylinders and moderate withdrawal to prevent solvent entrainment.Hence, acetylene is stored dissolved in acetone within a porous mass. Verification / Alternative check: Cylinder labels and safety data clearly indicate acetone-filled porous mass; regulators are sized for solution storage performance. Why Other Options Are Wrong: Pure compressed gaseous acetylene above low pressure is hazardous. Liquefaction by compression alone is not used; acetylene has no practical ambient-pressure liquefaction pathway for cylinders. Solid carbide blocks (e.g., calcium carbide) are for generating acetylene on demand in older generators, not for cylinder storage. Cryogenic storage is impractical and unnecessary in workshops. Common Pitfalls: Laying cylinders horizontally (causes solvent carryover); withdrawing gas too fast; using copper tubing with acetylene (risk of explosive copper acetylide formation above certain percentages). Final Answer: dissolved in acetone within a porous mass (solution storage)

Question 9

Oxy–acetylene practice — applications of a neutral flame: A neutral flame (approximately equal oxygen and acetylene) is generally suitable for welding which of the following materials?

Accepted Answer

Introduction / Context: A neutral flame is produced when oxygen and acetylene are supplied in roughly equal proportions, eliminating excess oxygen (oxidising) or excess acetylene (carburising). Selecting the correct flame type is crucial to minimise oxidation, decarburisation, or carburisation of the base metal during welding. Given Data / Assumptions: We consider common workshop welding of steels, cast irons, and coppers. No special fluxes or proprietary gas mixes are assumed. Joint preparation and preheat requirements may still apply. Concept / Approach: A neutral flame neither adds carbon to the weld pool nor scavenges it, making it a safe default for many ferrous and non-ferrous metals. Mild and low-alloy steels, cast irons (with appropriate preheat and technique), and copper can be welded with a neutral flame to control metallurgical side effects. Some special cases may use slightly oxidising (for copper deoxidation) or slightly carburising (for aluminium bronze), but the general-purpose, exam-level answer remains the neutral flame for all three materials listed. Step-by-Step Solution: Define neutral flame: balanced oxygen and acetylene, with a well-defined inner cone and no feather.Assess material response: steel and cast iron dislike excessive oxidation; copper oxidises readily but can be welded neutrally with flux.Conclude that a neutral flame is broadly applicable to steel, cast iron, and copper. Verification / Alternative check: Welding handbooks list neutral flame as the baseline for steels and as acceptable for cast iron and copper with appropriate fluxes and preheat management. Why Other Options Are Wrong: Restricting to only one metal ignores standard practice. “None of these” contradicts well-known applications of neutral flame. Common Pitfalls: Using an oxidising flame on steels leading to brittle welds; failing to preheat cast iron sufficiently; not using deoxidising flux on copper, which increases porosity risk. Final Answer: all of these

Question 10

Resistance welding sequence — force and current timing: In resistance spot/seam welding, when should electrode pressure be applied relative to the welding current?

Accepted Answer

Introduction / Context: Resistance welding depends on heat generated by electrical resistance at the faying surfaces, combined with mechanical force to ensure intimate contact and containment of the molten nugget. Correct timing of electrode force and current is vital for nugget formation and joint quality. Given Data / Assumptions: Standard spot or seam welding with copper alloy electrodes. Weld cycle includes squeeze time, weld time, and hold time. Goal: produce a consistent solidified nugget with minimal expulsion. Concept / Approach: The classic sequence is: apply electrode force first (squeeze) to ensure close contact and stable resistance; then pass current for a set weld time to form the molten nugget; finally hold the force for a hold time while current ceases so the nugget solidifies under pressure, preventing porosity and expulsion. Applying force only after current would cause arcing and spatter, while releasing force during current destabilises the nugget. Step-by-Step Solution: Squeeze: apply and stabilise force before current.Weld: maintain force while current flows to form the nugget.Hold: maintain force briefly after current to consolidate and solidify.Therefore, pressure must be applied and held before, during, and briefly after current flow. Verification / Alternative check: Most weld controllers let you program squeeze, weld, and hold times explicitly, reflecting this standard sequence. Why Other Options Are Wrong: Applying pressure only after current risks surface arcing and expulsion. No-pressure claims contradict the fundamental principle of resistance welding. Applying force only after solidification prevents proper nugget formation. Releasing force during current destabilises the nugget and increases spatter. Common Pitfalls: Insufficient squeeze time; too short hold time causing shrinkage voids; worn electrode tips increasing contact area and lowering current density. Final Answer: pressure is applied and held before, during, and briefly after current flow

Question 11

Layout tools — primary use of a scribing (surface) block: In bench layout on a surface plate, a scribing block is primarily used to

Accepted Answer

Introduction / Context: Bench layout relies on a flat reference (surface plate) and height-based marking to transfer dimensions to workpieces. The scribing (surface) block, often with a scriber and fine adjustment, is central to this process. Knowing its primary purpose avoids misuse and improves layout accuracy. Given Data / Assumptions: A standard surface plate and scribing block with adjustable scriber. Work requires parallel lines, datum transfers, or height-based marking. Ancillary tools like V-blocks can be used with it when needed. Concept / Approach: The scribing block is essentially a height gauge for marking. It sets a precise height relative to the surface plate and draws or transfers lines onto the work. While it can help check flatness by feel against the plate and can assist in finding centres of round bars when used with a V-block, its primary, exam-definitive function is accurate height-based scribing and layout. Step-by-Step Solution: Place work on the surface plate and set required scriber height on the scribing block.Move the block along the plate to mark a parallel line at the set height.Use auxiliary V-blocks to support round bars if centre lines are required.Therefore, the principal use is to mark accurate layout lines at a set height. Verification / Alternative check: Tool catalogues classify scribing blocks/surface gauges under marking-out tools, not holding or direct roughness measurement tools. Why Other Options Are Wrong: Holding round bars is the function of V-blocks, not the scribing block. Surface roughness is measured with comparators or profilometers. Locating centres of round bars requires a V-block and scribing block together; the block alone is insufficient. Thread pitch measurement uses thread gauges, not scribing blocks. Common Pitfalls: Dragging chips under the base and scratching the surface plate; using a blunt scriber leading to thick, inaccurate lines; failing to clamp the scriber height properly before marking. Final Answer: mark accurate layout lines at a set height from the reference surface

Question 12

Metrology fixtures — function of a V-block: In inspection and marking work, a V-block is primarily used to

Accepted Answer

Introduction / Context: V-blocks are precision fixtures with a 90-degree V-groove used extensively for holding cylindrical work. They are indispensable during inspection, layout, and light machining because they provide stable and repeatable location for round sections. Given Data / Assumptions: Standard V-block with clamp. Operations include marking centre lines, concentricity checks, and light machining or drilling. Use on a surface plate or drill press table. Concept / Approach: The V-groove supports a cylindrical workpiece along two lines of contact, centring it with respect to the block. When used with a scribing block, it enables accurate centre-line marking. In inspection, it provides a repeatable nest for dial indicator checks. It is not used to measure roughness or angles directly; other gauges are required for those tasks. Step-by-Step Solution: Place the round bar in the V-groove; clamp if needed.Use a scribing block to mark diametral lines or to find the centre.Alternatively, set up a dial indicator to check runout while rotating the bar.Hence, V-blocks primarily locate and support round rods for marking or inspection. Verification / Alternative check: Inspection manuals list V-blocks as supports for cylindrical work, not for surface roughness or general flatness testing. Why Other Options Are Wrong: Flatness checks use surface plates, straight edges, and feeler gauges, not V-blocks. Surface roughness requires comparators or stylus instruments. Angle measurement needs protractors, sine bars, or angle gauges. Sheet holding for shearing is a function of the shear's hold-down, not V-blocks. Common Pitfalls: Forgetting to deburr the bar before seating; using damaged V-blocks that introduce error; not clamping during drilling leading to spinning of the work. Final Answer: locate centres of round rods or support them for machining/inspection

Question 13

Foundry gating — name the vertical channel: In sand casting, which gating element carries molten metal from the pouring basin down to the runner/gate system?

Accepted Answer

Introduction / Context: Effective gating design ensures smooth, turbulence-minimised flow of molten metal into the mould cavity. The principal elements include the pouring basin, sprue, runner, gates, and risers. Identifying each element's function is a foundational foundry skill. Given Data / Assumptions: Conventional green-sand mould with top pouring basin. Gravity-fed system; no pressurised gating. Standard terminology for gating components. Concept / Approach: The pouring basin receives metal from the ladle and dampens turbulence. The sprue is the vertical channel that conducts metal downward from the basin to the runner. The runner distributes metal horizontally to the gates, which finally feed the cavity. Risers are reservoirs that compensate for shrinkage during solidification. Cores form internal cavities; chills control local solidification by rapid heat extraction. Step-by-Step Solution: Trace flow path: Ladle → Pouring basin → Sprue (vertical) → Runner (horizontal) → Gate → Cavity.Identify vertical element: the sprue.Therefore, the component delivering metal from basin to the gate system is the sprue. Verification / Alternative check: Standard foundry diagrams consistently name the vertical down-run as the sprue and distinguish it from risers and runners. Why Other Options Are Wrong: Riser feeds the casting during solidification; it is not a delivery channel from the basin. Core forms internal cavities; it is not a gating element for flow delivery. Chill is a heat sink, not a channel. Skim bob is a special feature for slag entrapment, not the main downsprue. Common Pitfalls: Confusing sprue with riser because both are vertical; ignoring the need for a tapered sprue to avoid aspiration; omitting a well at the sprue base, causing erosion. Final Answer: sprue

Question 14

Limits and fits — definition of a basic shaft: In the ISO system of limits and fits, a basic shaft is defined as a shaft whose

Accepted Answer

Introduction / Context: Limits and fits establish interchangeability between mating parts by specifying permissible size variations (tolerances) and positions (deviations) relative to a zero line (basic size). Understanding the definitions of a basic hole and a basic shaft is fundamental to selecting fit systems. Given Data / Assumptions: ISO system with deviation symbols: ES, EI for holes; es, ei for shafts. Basic size is the nominal dimension. Zero line represents the basic size. Concept / Approach: In a basic hole system, the lower deviation of the hole (EI) is zero, so hole tolerance zone starts at the basic size. Conversely, in a basic shaft system, the upper deviation of the shaft (es) is zero, so the shaft tolerance zone ends at the basic size on the upper side. This simplifies tooling and gauging strategies based on whether holes or shafts are standardised. Step-by-Step Solution: Recall definitions: Basic hole → EI = 0; Basic shaft → es = 0.Translate to wording: Basic shaft has zero upper deviation.Therefore, the correct statement is that the upper deviation is zero. Verification / Alternative check: Look up ISO 286: diagrams show the shaft tolerance zone touching the zero line at its upper limit when using a basic shaft. Why Other Options Are Wrong: Lower deviation zero refers to a basic hole, not a basic shaft. Both deviations zero would imply no tolerance, which is impractical. Symmetry about zero is not a general rule for basic shaft. Relative size to the hole depends on the intended fit (clearance, transition, interference), not on the definition of basic shaft. Common Pitfalls: Mixing up EI/ES with ei/es; assuming basic shaft means fixed shaft size—only the deviation position is fixed; forgetting that fit selection also depends on manufacturing capability and functional requirements. Final Answer: upper deviation is zero

Question 15

Sheet-metal operations — definition of piercing: In press working terminology, piercing is the operation of cutting

Accepted Answer

Introduction / Context: Punching operations are categorised by which part is retained as the product. Accurate terminology avoids confusion in tooling design, cost estimation, and scrap handling. Piercing and blanking are frequently confused in introductory manufacturing courses. Given Data / Assumptions: A punch–die set operates on sheet/strip metal. Clearance is correctly set for material and thickness. We are classifying the operation by the intended product. Concept / Approach: In piercing, a hole is created in the sheet; the removed piece (slug) is scrap. The hole may be circular or of any other profile. In blanking, the piece that is cut out (the blank) is the product, and the remaining sheet is scrap. Multiple-hole patterns are achieved by multiple hits or special tooling but are still fundamentally piercing operations. Step-by-Step Solution: Define piercing: create a hole; keep the sheet; discard the slug.Contrast with blanking: keep the slug (blank); discard the surrounding sheet.Recognise that shape can be circular or non-circular; piercing is not limited to cylinders.Hence, the correct definition is cutting a hole of any required shape using punch and die with slug as scrap. Verification / Alternative check: Tooling handbooks classify piercing and blanking based on which portion is retained; example drawings show identical punch/die but different intended products. Why Other Options Are Wrong: Restricting to cylindrical holes is unnecessary; any shape can be pierced. Blanking describes making the product blank, not piercing. Evenly spaced patterns can be produced, but that is not the defining feature. Punching does not create threads; threading is a separate operation (tapping/forming). Common Pitfalls: Mis-setting clearance, causing burrs and short tool life; ignoring slug ejection and disposal; failing to support the sheet properly, leading to distortion around the hole. Final Answer: a hole of any required shape in sheet metal using a punch and die (the slug is scrap)

Question 16

Materials engineering — strengthening by deformation: The increase in hardness and strength produced by plastic deformation at room (or low) temperature is called

Accepted Answer

Introduction / Context: Many manufacturing processes intentionally deform metals below recrystallisation temperature to improve strength and hardness. Understanding the terminology and mechanism of this strengthening method is fundamental for process planning (e.g., rolling, drawing, bending) and for deciding when to anneal between passes. Given Data / Assumptions: Plastic deformation at room or moderately elevated temperatures. No phase transformation or diffusion-based ageing is involved during the deformation itself. Material is typically a ductile metal such as steel, aluminium, or copper alloys. Concept / Approach: Work-hardening (also called strain hardening or cold work) increases dislocation density. Interactions among dislocations impede further movement, raising the flow stress, yield strength, and hardness while reducing ductility. The effect can be reversed or reduced by recovery and recrystallisation during subsequent annealing. This is distinct from age-hardening (precipitation hardening), which depends on controlled heat treatment that forms fine precipitates to impede dislocations, and from surface hardening methods like induction or flame hardening that transform only surface layers by rapid heating and quenching. Step-by-Step Solution: Apply plastic strain below recrystallisation temperature to raise dislocation density.Increased dislocation interactions elevate yield and hardness.Recognise the trade-off: ductility and toughness decrease with cold work.Therefore, the correct term for hardness increase by deformation is work-hardening. Verification / Alternative check: Tensile tests on cold-rolled vs. annealed samples show higher yield strength and lower elongation for the cold-worked material, confirming strain hardening. Why Other Options Are Wrong: Age-hardening requires solution treatment and ageing, not immediate deformation. Induction and flame hardening are thermal surface treatments relying on martensitic transformation in steels. Solution strengthening depends on solute atoms in solid solution, not on deformation alone. Common Pitfalls: Overworking without intermediate anneals, leading to cracking; assuming work-hardened parts retain ductility; forgetting springback increases with higher strength after cold work. Final Answer: work-hardening

Question 17

Foundry processes — identifying the permanent mould casting method Select the description that correctly corresponds to the permanent mould (gravity die) casting process used in manufacturing.

Accepted Answer

Introduction / Context: Permanent mould casting, often called gravity die casting, is a key manufacturing process where a reusable metal mould is used and molten metal is poured by gravity. This question tests your ability to distinguish permanent mould casting from related processes such as slush casting, centrifugal casting, and pressure die casting. Given Data / Assumptions: A permanent mould is metallic and reusable. Metal is poured by gravity (no high external pressure, and no mould rotation). The distractors describe other well-known processes. Concept / Approach: Match each description to its process definition. Permanent mould (gravity die) casting is simply pouring metal into a heated metal mould and allowing it to solidify completely under gravity, then opening the mould to remove the solid casting. No inversion to drain liquid core, no high-pressure injection, and no mould rotation are involved. Step-by-Step Solution: Identify option (a): draining the liquid core after a skin forms is the hallmark of slush casting used for thin hollow decorative parts.Identify option (b): solidification during mould rotation is centrifugal casting, typically for pipes, bushings, or rings.Identify option (c): forcing metal under high pressure is pressure die casting (hot- or cold-chamber machines).Permanent mould (gravity die) casting involves none of the above additional actions; therefore, among listed choices, the correct response is 'None of the above.' Verification / Alternative check: Process selection charts list gravity die casting as a medium-to-high rate process with reusable metallic dies and gravity feed, distinct from pressure die casting (pressure fed), centrifugal casting (rotating), and slush casting (drain-out technique). Why Other Options Are Wrong: (a) Describes slush casting, not gravity die casting. (b) Describes centrifugal casting, not gravity die casting. (c) Describes pressure die casting with high injection pressures, unlike gravity feed. (e) Describes a nonstandard method and not the accepted definition of permanent mould casting. Common Pitfalls: Confusing the term 'die' to mean only high-pressure die casting; believing all metal mould processes are identical; overlooking that gravity die casting solidifies fully inside the die without draining or rotation. Final Answer: None of the above.

Question 18

Gas welding technique — torch/rod angle comparison In back-hand (rightward) oxy-acetylene welding, the angle between the welding rod/torch and the work surface is __________ compared to fore-hand (leftward) welding.

Accepted Answer

Introduction / Context: In oxy-acetylene welding, torch position and filler rod angle influence heat distribution, puddle control, and penetration. Two classic techniques are fore-hand (leftward) and back-hand (rightward) welding. This item focuses on the typical difference in torch/rod angle between these techniques. Given Data / Assumptions: Fore-hand welding leads the flame in the direction of travel. Back-hand welding trails the flame behind the puddle. Typical recommended angles differ in standard practice. Concept / Approach: Fore-hand welding commonly uses a smaller torch angle to the work (for example about 40°–50°). Back-hand welding typically increases the angle (for example about 60°–70°) to direct more heat into the solidifying bead and improve penetration on thicker sections. Step-by-Step Solution: Compare techniques: fore-hand uses a smaller included angle; back-hand uses a larger one.Purpose: larger angle in back-hand concentrates heat behind the puddle, aiding fusion and penetration.Conclusion: the angle in back-hand welding is more than in fore-hand welding. Verification / Alternative check: Standard welding handbooks illustrate rightward technique with a steeper torch inclination than leftward technique, consistent with the need for deeper penetration and improved bead contour on thicker plate. Why Other Options Are Wrong: 'Less' and 'same' contradict common procedure guides; 'variable but smaller/equal' mischaracterizes the typical recommendation. Common Pitfalls: Holding the torch too vertical causing excessive surface heating; copying angles blindly without adapting to joint type and thickness; forgetting to coordinate travel speed with angle changes. Final Answer: more

Question 19

Foundry terminology — three-part mould patterns When a pattern is made in three parts, the top part of the mould assembly is called the __________.

Accepted Answer

Introduction / Context: In sand moulding, the flask (or mould box) may consist of two or three parts depending on the complexity of the casting. Understanding standard names improves communication between design and foundry teams. Given Data / Assumptions: Three-part mould box is used (top, middle, bottom sections). Pattern may require a cheek to split complex geometry. Standard foundry nomenclature is assumed. Concept / Approach: The conventional names are: top part = cope, bottom part = drag, and the middle section (if present) = cheek. Core prints and sprue are separate features used for core location and metal entry, not flask parts. Step-by-Step Solution: Identify the top section term: cope.Identify the bottom section term: drag.Identify the intermediate section term: cheek.Therefore, for the top part, select 'cope'. Verification / Alternative check: Any standard foundry text or shop documentation labels the three-part assembly as cope-cheek-drag in that order from top to bottom. Why Other Options Are Wrong: Cheek refers to the middle section; drag refers to the bottom; core print and sprue are not flask parts. Common Pitfalls: Confusing pattern components with flask components; assuming sprue is a flask part; overlooking that two-part moulds do not include a cheek. Final Answer: cope

Question 20

Arc welding processes — molten weld pool usage Which of the following welding processes explicitly uses and maintains a molten weld pool during operation?

Accepted Answer

Introduction / Context: Most fusion welding processes create a molten weld pool. However, some examinations highlight the distinctive feature of a process. Submerged arc welding (SAW) is notable for a molten metal pool protected under a thick blanket of granular flux, invisible to the operator, which is a common test point. Given Data / Assumptions: All listed processes are fusion welding methods. Question emphasizes the method commonly associated with a controlled flux-covered molten pool. Conventional terminology and shop practice are assumed. Concept / Approach: While TIG and MIG also form molten pools, SAW is pedagogically identified with a continuously maintained molten pool submerged under flux, enabling high deposition rates and deep penetration without arc glare. Step-by-Step Solution: Recall SAW setup: continuously fed wire, DC/AC power, granular flux forms a protective blanket.Under this flux, a molten pool exists along with molten slag, producing smooth welds and high productivity.Therefore, select the process most characteristically described by a flux-covered molten pool: SAW. Verification / Alternative check: Process descriptions consistently illustrate SAW with a hidden arc and molten pool beneath the flux. TIG and MIG display an open, visible pool shielded by inert gas instead of granular flux. Why Other Options Are Wrong: Carbon arc, TIG, and MIG certainly create a molten pool, but they are not defined by a submerged pool; the exam emphasis often points to SAW for this descriptor. 'All of the above' dilutes the distinctive identification the question seeks. Common Pitfalls: Assuming that because many fusion processes have pools, all are equally correct; overlooking the key word 'submerged' that is uniquely tied to SAW. Final Answer: Submerged arc welding (granular flux covering)

Workshop Technology Questions