Question 1

In die casting process selection, a hot-chamber (gooseneck) die casting machine is typically used for casting which category of alloys based on melting temperature and reactivity with the machine’s immersed components?

Accepted Answer

Introduction / Context: Die casting employs either hot-chamber or cold-chamber machines. The choice depends primarily on the alloy’s melting temperature and its chemical attack on the machine hardware. Understanding this selection is fundamental in manufacturing process planning for components like housings, gears, and covers. Given Data / Assumptions: Hot-chamber machines immerse the injection mechanism (gooseneck) in the molten metal bath. Concerns include corrosion/erosion of immersed parts and thermal limits. Common die-cast alloys include Zn, Mg, Al, Cu-based systems (with variations). Concept / Approach: Hot-chamber die casting is ideally suited to low-melting, non-ferrous alloys that do not excessively attack the immersed gooseneck components—classically zinc and some magnesium alloys. Alloys like aluminum and brass/bronze (higher melting and more reactive) are typically cast in cold-chamber machines to avoid hardware degradation and to handle higher temperatures. Step-by-Step Solution: 1) Identify machine constraint: immersed injection hardware limits allowable melt temperature and chemistry.2) Map alloys: Zn, Mg (lower Tm) → hot chamber; Al, Cu (higher Tm or reactive) → cold chamber.3) Conclude: hot-chamber is for non-ferrous, low-melting alloys. Verification / Alternative check: Process charts in manufacturing texts show Zn die castings predominantly using hot-chamber machines; Al die castings generally use cold-chamber machines. Why Other Options Are Wrong: Ferrous alloys: die casting is not used for ferrous alloys at typical machine limits. Non-ferrous high-melting: favors cold-chamber due to temperature and reactivity. Superalloys: unsuitable for standard die casting hardware and temperatures. Common Pitfalls: Assuming aluminum is always hot-chamber; it is predominantly cold-chamber. Final Answer: non-ferrous alloys with low melting temperature

Question 2

Gas welding safety and gas generation: The statement ‘‘Low-pressure acetylene for welding is produced at the job site by the chemical reaction between water and calcium carbonate’’ is — choose the correct assessment based on standard carbide generat…

Accepted Answer

Introduction / Context: Acetylene (C2H2) is a common fuel gas in oxy–acetylene welding. Historically, portable generators produced acetylene on site. Knowing the correct reactants is vital for both safety and exam accuracy. Given Data / Assumptions: ‘‘Low-pressure acetylene’’ refers to generator-produced gas (legacy practice). Question cites water reacting with calcium carbonate. Standard generator chemistry should be applied. Concept / Approach: The canonical reaction in acetylene generators is between water and calcium carbide (CaC2): CaC2 + 2H2O → C2H2 + Ca(OH)2. Calcium carbonate (CaCO3) does not yield acetylene upon contact with water; it is limestone and would require acid to evolve CO2, not C2H2. Therefore, the statement is incorrect. Step-by-Step Solution: 1) Recall correct reagent: calcium carbide, not calcium carbonate.2) Write the reaction with water: CaC2 + 2H2O → C2H2 + Ca(OH)2.3) Conclude the provided statement is false because CaCO3 cannot produce acetylene with water. Verification / Alternative check: Industrial practice has largely shifted to dissolved acetylene in cylinders (acetone/DMF), but where on-site generation is used, the reagent remains CaC2, confirming the correction. Why Other Options Are Wrong: Correct / Conditionally correct / Lab-grade / Cylinder-based: all contradict the fundamental chemistry; cylinders contain dissolved acetylene, not generated from CaCO3 on site. Common Pitfalls: Confusing carbide with carbonate due to similar names. Assuming any calcium compound with water can produce acetylene—only CaC2 does. Final Answer: Incorrect

Question 3

Foundry cores and parting: When a hole or internal cavity to be formed by a core is not aligned with (i.e., does not lie on) the mould’s parting surface, which specific type of core arrangement is used to place and support the core accurately?

Accepted Answer

Introduction / Context: In sand casting, cores create internal cavities. When these cavities are located away from the parting plane, special core seating and support methods are required to position the core correctly without damaging the mould or causing misalignment during assembly and pouring. Given Data / Assumptions: The cavity axis does not coincide with the parting surface. Core must be placed after the cope and drag are separated and reassembled. Goal is accurate, repeatable location of the core. Concept / Approach: A drop core is used when the core cannot be supported by the natural parting. It employs special seats, core prints, and possibly chaplets, allowing the core to be lowered (‘‘dropped’’) into place within the mould cavity and properly located away from the parting plane. By contrast, horizontal/vertical core terms describe orientation rather than the off-parting placement method; a balanced core refers to weight distribution, not location strategy. Step-by-Step Solution: 1) Identify constraint: core location not on parting plane.2) Choose a method that allows insertion after mould opening: drop the core into its dedicated recess.3) Hence, select a drop core arrangement. Verification / Alternative check: Foundry practice texts list drop cores for off-parting cavities, using core prints and sometimes loose pieces to enable assembly. Why Other Options Are Wrong: Horizontal/Vertical core: describe orientation, not the off-parting placement solution. Balanced core: addresses stability/weight; not the placement challenge. Rocker core: a special mechanism for complex withdrawals; not the standard answer for off-parting cavities. Common Pitfalls: Confusing core orientation terms with assembly/placement methods. Overusing chaplets instead of proper core-print design for location. Final Answer: drop core

Question 4

In physical metallurgy and heat treatment, the temperature at which new, strain-free grains nucleate and grow to replace deformed grains during recovery/annealing is termed what?

Accepted Answer

Introduction / Context: Cold working introduces a high density of dislocations and stored energy into metals, increasing strength and reducing ductility. Subsequent heat treatment can reverse these effects through recovery and recrystallisation, restoring ductility by forming new, strain-free grains. Recognizing the temperature associated with this transformation is essential for process design. Given Data / Assumptions: Material has been plastically deformed (cold worked). Heating occurs below the melting point. Observation concerns the onset of new grain formation. Concept / Approach: The recrystallisation temperature is the temperature (often expressed as a range) at which new, equiaxed, strain-free grains nucleate and grow to replace the deformed microstructure within a specified time (commonly one hour in definitions). It depends on prior cold work, purity, alloying, and grain size, frequently approximated as 0.3–0.5 Tm (absolute) for many metals. Step-by-Step Solution: 1) Identify the phenomenon: formation of new grains after cold work upon heating.2) Name the associated temperature: ‘‘recrystallisation temperature.’’3) Note that it is not a sharp point but a practical range influenced by material condition. Verification / Alternative check: Metallographic studies show nucleation at grain boundaries and high-energy sites; mechanical tests confirm ductility recovery near the recrystallisation range. Why Other Options Are Wrong: Upper/Lower critical temperature: refer to phase boundaries in steels (A3, A1), not to cold-work recovery. Eutectic temperature: invariant reaction temperature in phase diagrams, unrelated to recrystallisation. Solutionizing temperature: heat-treatment step for dissolving precipitates in alloys (e.g., aluminum), different purpose. Common Pitfalls: Assuming a single fixed value; it depends on prior deformation and composition. Confusing recrystallisation with grain growth; growth often follows after recrystallisation completes. Final Answer: recrystallisation temperature

Question 5

In submerged arc welding (SAW), the electric arc that melts the base metal is established between which electrode–workpiece combination, considering the granular flux fully blankets the arc zone?

Accepted Answer

Introduction / Context: Submerged arc welding (SAW) is a high-productivity fusion welding process where an arc burns beneath a pile of granular flux, shielding the molten pool from the atmosphere. Understanding the electrode type is key to differentiating SAW from shielded metal arc welding (SMAW) and gas–tungsten arc welding (GTAW). Given Data / Assumptions: Process uses a granular (fused or agglomerated) flux delivered ahead of the arc. The arc zone is invisible (submerged) during welding. Wire feed is continuous. Concept / Approach: SAW employs a continuous bare metal wire (consumable electrode) that feeds into the weld pool. The flux provides shielding, slag formation, and sometimes alloying; there is no external gas shield and no coated stick electrode like SMAW. Non-consumable electrodes (tungsten) are used in GTAW, not SAW; carbon electrodes are typical of older arc processes, not SAW. Step-by-Step Solution: 1) Identify process signature: granular flux blanket and continuous wire feed.2) Match electrode type: consumable bare metal wire (solid or sometimes tubular).3) Conclude the arc is between the bare metal electrode and the work. Verification / Alternative check: Process schematics show wire reel feeding into a flux pile with the current source connected to the wire and workpiece; the arc is thus wire-to-work beneath flux. Why Other Options Are Wrong: Tungsten electrodes: define GTAW, not SAW. Carbon electrode: used in carbon arc processes, not SAW. Heavy flux-coated stick: describes SMAW (stick welding), not the submerged continuous-wire method. Common Pitfalls: Assuming ‘‘submerged’’ implies non-consumable electrodes—SAW uses consumable bare wire. Final Answer: bare metal electrode and the work

Question 6

In hand tool operations for slotting and key seat preparation, which specific chisel form is preferred for cutting keyways with parallel sides and a flat bottom in shafts or hubs?

Accepted Answer

Introduction / Context: Keyways are prismatic slots machined in shafts or hubs to accommodate keys for torque transmission. While machine tools are commonly used, hand fitting and corrections often rely on chisels with geometries tailored to the slot profile. Given Data / Assumptions: Goal: produce/clean a narrow rectangular slot with parallel sides and a flat bottom. Work may involve deburring, minor enlargement, or finishing after drilling/slotting. Chisel operation performed along layout lines. Concept / Approach: The cape chisel has a narrow cutting edge and side clearance that enable it to cut grooves and keyways to width while maintaining sidewall parallelism. A flat chisel is wider and suited to general chipping; a round nose creates semicircular grooves; a diamond point is for corners and V-grooves. Thus, the cape chisel matches the keyway geometry. Step-by-Step Solution: 1) Identify required slot geometry: flat-bottom, parallel-sided groove.2) Select chisel with narrow edge and side relief to follow layout accurately → cape chisel.3) Use controlled hammering and frequent gauging to maintain width and depth. Verification / Alternative check: Fitting manuals show cape chisel shapes specifically for key seat work, confirming tool–task alignment. Why Other Options Are Wrong: Flat chisel: lacks side relief; risks widening beyond layout. Round nose: forms curved bottoms, not flat key seats. Diamond pointed: intended for corners/V-grooves and cleaning internal angles. Side cutting chisel: specialized for lateral cuts; not the standard keyway tool. Common Pitfalls: Failing to maintain chisel sharpness and correct rake/clearance angles, resulting in sidewall taper. Neglecting to support the work securely, causing chatter and misalignment. Final Answer: cape chisel

Question 7

Pattern terminology in sand moulding: When a pattern is constructed in three parts for complex geometry, the statement ‘‘the bottom part of the pattern assembly is known as a cope’’ is — select the correct evaluation using standard cope–drag–cheek n…

Accepted Answer

Introduction / Context: In sand casting, the moulding box (flask) is typically split into an upper half and a lower half; for more complex castings, a third middle section can be added. Understanding the standard names avoids assembly errors and miscommunication on the foundry floor. Given Data / Assumptions: Three-part pattern/mould arrangement. Conventional terminology is used throughout foundry practice. No inversion or special jigs altering naming conventions. Concept / Approach: The cope is the upper portion of the mould or pattern assembly; the drag is the lower portion; when present, the cheek is the middle section inserted between cope and drag. Therefore, calling the bottom part a ‘‘cope’’ is incorrect; the correct name is drag. Step-by-Step Solution: 1) Recall standard names: cope (top), drag (bottom), cheek (middle).2) Map statement: ‘‘bottom part is cope’’ contradicts the definitions.3) Conclude the statement is false. Verification / Alternative check: Foundry texts and shop practice consistently use cope/drag/cheek in this manner; gating and risering diagrams likewise label the halves accordingly. Why Other Options Are Wrong: True / conditional variants: conflict with universal nomenclature unless a hypothetical inverted labeling system is adopted (not standard). Common Pitfalls: Confusing flask orientation during handling with the naming convention, which remains fixed. Final Answer: False

Question 8

Centrifugal casting — in true centrifugal casting of hollow cylindrical parts, do inclusions, slag, and gas porosity tend to segregate toward the geometric centre (bore) of the casting due to radial acceleration?

Accepted Answer

Introduction / Context: Centrifugal casting is a foundry process used to produce hollow, axisymmetric parts such as pipes, sleeves, and rings. The mould rotates at high angular speed while molten metal is poured. The intense radial acceleration throws the denser liquid metal outward against the mould wall, shaping and solidifying the casting from the outside inward. This question probes whether impurities concentrate toward the centre (the bore) during this process. Given Data / Assumptions: True centrifugal casting (no core is used; the bore forms naturally). Molten metal contains typical contaminants: non-metallic inclusions, dross/slag, and dissolved gases that can form porosity. Steady rotation at a prescribed speed during pouring and solidification. Concept / Approach: Under rotation, the apparent body force per unit mass is ω²r directed radially outward. Denser phases (metal) experience greater outward driving than lighter phases (slag, oxide skins, entrapped gases). Consequently, lighter constituents tend to migrate toward the axis where the effective radial acceleration is smaller, leading to segregation near the centre. Solidification also begins at the mould wall, pushing remaining liquid—and with it lighter inclusions—toward the inner surface (bore). Step-by-Step Solution: 1) Pour molten metal into the rapidly rotating mould; metal is flung outward.2) The outer layer chills and solidifies first against the cold mould wall.3) As freezing fronts move inward, lighter inclusions/gases are rejected from the solid and migrate toward the centre.4) After solidification, any inclusion-rich layer at the bore can be machined away to meet quality requirements. Verification / Alternative check: Microstructural examinations and industry practice confirm denser, cleaner metal at the periphery and impurity concentration near the inner surface. Standards often specify machining allowance on the bore to remove this layer. Why Other Options Are Wrong: “No” is incorrect because both centrifugal segregation and directional solidification effects favour impurity concentration near the bore. Common Pitfalls: Confusing true centrifugal casting (hollow parts) with centrifuging/semi-centrifugal methods used for non-hollow geometries; assuming inclusions distribute uniformly. Final Answer: Yes

Question 9

Arc welding processes — which one of the following uses a non-consumable tungsten electrode to sustain the arc while the filler (if any) is added separately?

Accepted Answer

Introduction / Context: Identifying whether an electrode is consumable or non-consumable is fundamental to classifying arc welding processes and predicting bead characteristics, heat input, and metallurgical outcomes. Tungsten Inert Gas (TIG), also called Gas Tungsten Arc Welding (GTAW), is the canonical non-consumable electrode process. Given Data / Assumptions: Electrode types: consumable (melts, supplies filler) vs non-consumable (does not melt). Shielding: inert gases like argon/helium commonly used in TIG/MIG. Process names: TIG (GTAW), MIG (GMAW), Manual Metal Arc (SMAW), Submerged Arc (SAW). Concept / Approach: In TIG/GTAW, a tungsten electrode sustains the arc but is not intended to melt into the weld pool. Filler, when needed, is added separately as a rod. MIG/GMAW, SMAW, and SAW all employ consumable electrodes: the wire (MIG/SAW) or the coated stick (SMAW) melts to become filler metal. Thus, the presence of a tungsten electrode that remains essentially intact is the distinguishing feature of TIG. Step-by-Step Solution: 1) Map process to electrode behavior: tungsten (TIG) ≠ consumable.2) Recognize that MIG uses a continuously fed consumable wire.3) SMAW uses a flux-coated consumable stick; SAW uses a consumable wire under granular flux.4) Therefore, only TIG employs a non-consumable electrode. Verification / Alternative check: Welding handbooks and training curricula define TIG/GTAW by its use of non-consumable tungsten electrodes, with shielding by inert gases to prevent tungsten oxidation and weld contamination. Why Other Options Are Wrong: MIG, Manual arc (SMAW), and SAW all melt the electrode to supply filler; none uses a non-consumable electrode. Common Pitfalls: Confusing tungsten (non-consumable) with “TIG wire”; in TIG, any added filler is a separate rod, not the electrode itself. Final Answer: TIG welding

Question 10

Die casting machines — in a hot-chamber die casting machine, how is the melting pot arranged relative to the machine and shot system?

Accepted Answer

Introduction / Context: Hot-chamber and cold-chamber die casting differ primarily in how molten metal is delivered to the shot chamber. Recognizing the configuration of the melting pot helps determine which alloys can be cast and what cycle times and contamination risks are expected. Given Data / Assumptions: Hot-chamber machines typically cast low-melting, non-ferrous alloys (e.g., Zn, Mg, some Pb alloys). Cold-chamber machines are used for higher-melting alloys (e.g., Al, brass) where immersion of the shot system would cause erosion. Question asks specifically about the melting pot's arrangement in hot-chamber machines. Concept / Approach: In hot-chamber die casting, the shot cylinder/shot plunger and the gooseneck are immersed in a molten metal bath that is part of the machine—i.e., the melting pot is integral. Metal is drawn directly into the gooseneck and injected into the die each cycle, enabling very fast production rates. In contrast, cold-chamber machines ladle molten metal from a separate furnace into the shot sleeve each cycle. Step-by-Step Solution: 1) Identify process: hot-chamber → immersed gooseneck/shot system.2) Infer arrangement: the bath (melting pot) is built into the machine frame.3) Conclude that the melting pot is integral to the machine in the hot-chamber variant. Verification / Alternative check: Manufacturer diagrams of hot-chamber machines show the crucible/gooseneck assembly within the machine body with the plunger operating below the bath surface. Why Other Options Are Wrong: Separate furnace applies to cold-chamber machines; “any location” is overly broad; “high temperature and pressure is used” is ambiguous and not distinctive to hot-chamber (both variants use pressure, and “high temperature” is relative). Common Pitfalls: Assuming all die casting uses a separate furnace; confusing alloy limitations with machine architecture. Final Answer: melting pot is an integral part of the machine

Question 11

Press tool design — in which type of die can blanking and piercing operations be carried out simultaneously in a single press stroke at a single station?

Accepted Answer

Introduction / Context: Sheet-metal press operations rely on appropriate die selection to achieve productivity and tolerance goals. Blanking (removing the workpiece from sheet) and piercing (punching holes) are common cutting operations. The question focuses on which die type performs both simultaneously at one station in one stroke. Given Data / Assumptions: Operations considered: blanking and piercing (both cutting). Interest is in simultaneity at a single station. Die taxonomy: simple, progressive, compound, combination. Concept / Approach: A compound die performs two or more cutting operations (e.g., blanking and piercing) in one press stroke at one station, using multiple punches/dies arranged coaxially or in sequence within the same station. Progressive dies perform operations at successive stations as the strip indexes forward; combination dies mix one cutting with one forming operation in the same stroke; a simple die performs a single operation per stroke. Step-by-Step Solution: 1) Identify that both blanking and piercing are cutting operations.2) Recall die classifications and their defining characteristics.3) Map simultaneity at one station to “compound die”. Verification / Alternative check: Press tool design texts explicitly define compound dies as multi-cutting-operation tools functioning at one station per stroke. Why Other Options Are Wrong: Simple die → single operation only; progressive die → multiple stations; combination die → cutting + forming (not two cutting ops simultaneously). Common Pitfalls: Confusing “progressive” (multi-station) with “compound” (single-station multi-cutting); assuming “combination” means any two operations regardless of type. Final Answer: compound die

Question 12

Foundry feeding systems — what is the primary function of a riser in a casting mould with respect to volumetric shrinkage during solidification?

Accepted Answer

Introduction / Context: During solidification, most alloys undergo volumetric contraction. If liquid metal is not supplied to regions that are freezing, shrinkage cavities or dispersed porosity will form. Risers (feeders) are integral features in mould design to maintain soundness by compensating for this shrinkage. Given Data / Assumptions: A conventional sand mould with a gating system and one or more risers. Alloy exhibits positive solidification shrinkage. Directional solidification from thin sections toward the riser is intended. Concept / Approach: A riser is a reservoir of molten metal thermally and geometrically designed to remain liquid longer than the casting sections it feeds. As the casting solidifies and contracts, the riser supplies additional metal through feeding paths to avoid void formation. The riser must freeze last (modulus and insulation considerations) and be properly located to ensure effective feeding, after which it is removed by a finishing operation. Step-by-Step Solution: 1) Establish directional solidification: promote freezing from remote regions toward the riser.2) Size riser (Chvorinov’s rule/modulus method) to ensure later solidification than casting.3) During contraction, liquid flows from the hot riser to fill shrinkage in the solidifying casting.4) After complete solidification, the riser is removed and the surface is finished. Verification / Alternative check: Soundness evaluation (radiography, sectioning) shows reduced shrinkage porosity when risers are correctly designed and placed. Why Other Options Are Wrong: (a) and (d) describe gating functions (sprue, runners, ingates), not feeding. (b) is partially true but incomplete; the essence is feeding to compensate shrinkage (option c). Common Pitfalls: Using oversized risers that raise yield loss; placing risers without thermal analysis, leading to ineffective feeding paths. Final Answer: feed the molten metal to the casting in order to compensate for the shrinkage

Question 13

Rolling mills — in a four-high mill configuration, which rolls act directly on the strip and which provide stiffness to limit deflection?

Accepted Answer

Introduction / Context: Rolling mill configurations are chosen to balance strip thickness control, surface quality, stiffness, and power requirements. The four-high mill is a common arrangement for cold rolling thin strip while maintaining adequate stiffness by using backup rolls to support smaller work rolls. Given Data / Assumptions: Four-high mill with two small-diameter rolls in the middle and two larger rolls outside. Objective: reduce strip thickness while controlling roll deflection and spreading. Standard definitions: “work (working) rolls” contact the strip; “backup” rolls support work rolls. Concept / Approach: The two central small-diameter rolls directly contact and deform the strip (work rolls). Their small diameter lowers rolling force and power but increases the tendency to bend, potentially causing crown/shape defects. To counter this, large-diameter backup rolls are placed above and below the work rolls to stiffen the system and limit elastic flattening. Step-by-Step Solution: 1) Identify roles: the inner pair (work rolls) contact strip; outer pair (backup rolls) provide support.2) Infer advantage: smaller work rolls reduce separating force; backups maintain geometric stability.3) Conclude that two work rolls and two backups define the configuration. Verification / Alternative check: Plant schematics and textbooks depict four-high mills exactly as “work–backup–work–backup”. Why Other Options Are Wrong: Options with one or three work rolls misrepresent the symmetric arrangement; “all four working” corresponds to a four-roll mill without backups, not the standard four-high configuration. Common Pitfalls: Confusing a “cluster” (Sendzimir/Z-mill) with a four-high; mislabeling backup rolls as idle elements—they are essential for stiffness. Final Answer: two are working rolls and two are backing up rolls

Question 14

Arc initiation in welding — the electric arc between electrode and workpiece is initially established primarily by which electrical factor under typical manual or mechanized arc-welding conditions?

Accepted Answer

Introduction / Context: The welding arc is a sustained electrical discharge through an ionized gas (plasma) between the electrode and the work. Understanding what initiates the arc helps with parameter selection (open-circuit voltage, arc length) and troubleshooting difficult starts. Given Data / Assumptions: Power source provides an open-circuit voltage (OCV) adequate for breakdown of the air gap. Once the arc is established, current flow sustains and heats the arc column. Contact resistance during striking contributes to local heating when touching/scratching to start the arc. Concept / Approach: Arc initiation requires dielectric breakdown of the gap, achieved when the instantaneous voltage across the gap exceeds the breakdown threshold (dependent on arc length, gas composition, pressure). Thus, sufficient OCV is critical to ionize the path. After initiation, the power source transitions to a lower arc voltage at the commanded welding current, and current becomes the dominant factor for heat input and droplet transfer. Contact resistance may assist by preheating during the scratch/tap start but is not the primary governing factor in gap breakdown. Step-by-Step Solution: 1) Approach work with electrode; a small air gap exists.2) The source OCV provides high electric field; when breakdown occurs, plasma forms.3) Arc is established; source regulates current/voltage to sustain stable welding. Verification / Alternative check: Manufacturer specifications list minimum OCV requirements (e.g., ~50–80 V for SMAW) to ensure reliable arc striking, confirming the primacy of voltage in initiation. Why Other Options Are Wrong: “Flow of current” sustains heat after initiation but cannot occur across an insulating gap without prior breakdown. “Contact resistance” helps during touch start but is auxiliary. “All of these” overstates roles; initiation is primarily a voltage (breakdown) phenomenon. Common Pitfalls: Confusing arc starting (breakdown) with arc heating (current); assuming high current alone can jump a gap without adequate OCV. Final Answer: voltage

Question 15

Tube manufacturing — which processes are suitable for producing ~2 m long seamless metallic tubes (no longitudinal weld seam)?

Accepted Answer

Introduction / Context: Seamless tubes lack a longitudinal weld and are therefore produced by plastic deformation routes that create or elongate a hollow from a solid billet or bloom. The question asks which methods can be used to manufacture seamless tubes of about 2 m length—a common industrial size for mechanical and heat-transfer applications. Given Data / Assumptions: Target product: seamless tube (no weld seam). Length: roughly 2 m (not limiting for most mill processes). Conventional primary processes considered: drawing, extrusion, rolling. Concept / Approach: Seamless tubes are commonly produced by: (i) extrusion using a mandrel or piercing plug to form a hollow and push metal through an annular die; and (ii) rolling routes such as Mannesmann rotary piercing followed by elongator/plug/mandrel mills to roll the shell to final size. Cold drawing is typically a secondary sizing/finishing step applied to a previously formed hollow (extruded or pierced) rather than the primary method for making a seamless hollow from solid. Hence, the most appropriate answer is the combination of extrusion and rolling as primary manufacturing routes. Step-by-Step Solution: 1) Create a hollow: rotary piercing (rolling) or extrusion over a mandrel.2) Elongate and size: plug/mandrel rolling mills or further extrusion passes.3) (Optional) Cold draw for tight tolerances/surface finish after primary forming. Verification / Alternative check: Industrial practice across steel and non-ferrous mills uses Mannesmann process (rolling) or direct extrusion to produce seamless hollows, frequently followed by cold finishing. Why Other Options Are Wrong: Drawing alone typically requires a starting hollow; rolling or extrusion are the primary “seamless” creators. Selecting only one of extrusion or rolling ignores the commonality of both as valid primary routes. Common Pitfalls: Equating tube drawing with initial hollow formation; forgetting that drawing is predominantly a finishing/sizing process for seamless tubes. Final Answer: Extrusion and rolling

Question 16

Forging tools — fullers are primarily used for which operation during hot-work to control metal flow and cross-section?

Accepted Answer

Introduction / Context: In smithy and forging practice, specialized tools are used to direct metal flow efficiently. Fullers (top and bottom) are rounded-groove tools that indent hot stock to redistribute material. Knowing their primary function is essential for planning preform shapes prior to drawing, bending, or upsetting operations. Given Data / Assumptions: Hot-working conditions with fullers used in pairs (bottom fuller in anvil/hardy hole and top fuller under hammer/press). Objective: locally reduce section or create shoulders/grooves to facilitate subsequent shaping. Distinguish from punches and drifts used for hole making/finishing. Concept / Approach: Fullering produces localized thinning and spreading of metal away from the groove, effectively necking down the work. The fuller impression encourages longitudinal flow on either side, creating a reduced section (a neck) and raised fillets/shoulders that can later be dressed by flattening or swaging. It is a preparatory step for controlled elongation and for defining transition radii. Step-by-Step Solution: 1) Heat the workpiece to forging temperature.2) Position the stock over the bottom fuller and strike the top fuller to indent.3) Work progressively along the intended necking line to achieve uniform reduction.4) Follow with drawing or planishing to smooth and reach final dimensions. Verification / Alternative check: Shop manuals depict fullering as the standard method for necking and shoulder formation, whereas punches/drifts are specified for hole creation/enlargement and bottom/top swages for finishing radiused sections. Why Other Options Are Wrong: Finishing flat surfaces is done with flatters; punching is done with punches; finishing holes is done with drifts/reamers—not fullers. Common Pitfalls: Using a fuller to finish surfaces (leaves grooves); forgetting to follow fullering with dressing to remove marks. Final Answer: for necking down a piece of work

Question 17

Hand cutting tools — the usual cross-sectional shape of a general-purpose cold chisel shank used by fitters is:

Accepted Answer

Introduction / Context: Cold chisels are chiselling and trimming tools used at room temperature on metals. The shank’s cross-section affects grip comfort, resistance to twisting, and the tool’s ability to withstand repeated hammer blows without excessive burr formation on the head. A common exam point is the standard cross-sectional geometry of the chisel shank. Given Data / Assumptions: General-purpose flat cold chisel (not specialized cape/round-nose variants). Hand striking with a hammer; need for ergonomic grip and anti-rolling features. Traditional forged tool-steel construction, later heat-treated. Concept / Approach: The octagonal cross-section offers multiple flats for secure hand grip and reduces the likelihood of rolling compared with round or square sections. It balances material usage and strength while providing comfortable indexing for the user’s fingers. While some chisels may be produced with hexagonal sections, the most widely cited standard for fitter’s cold chisels is an octagonal shank. Step-by-Step Solution: 1) Consider ergonomic requirements: multiple flats improve grip and control.2) Consider mechanical requirements: sufficient section modulus to resist bending under impact.3) Select the geometry that best meets both: octagonal. Verification / Alternative check: Commercial catalogues and workshop manuals list “octagonal shank” as the default for flat/hand chisels, with hexagonal seen on some manufacturers but less universal. Why Other Options Are Wrong: Rectangular and square sections are less ergonomic and more prone to edge damage; hexagonal is seen but is not the usual textbook answer for general-purpose cold chisels. Common Pitfalls: Assuming any polygonal cross-section is equally standard; overlooking that exam convention typically expects “octagonal”. Final Answer: octagonal

Question 18

In manufacturing metrology and gauging practice, is the following statement correct: ‘‘A plug gauge is used to check the diameter (external size) of shafts and studs’’—or is a different gauge type intended for such external measurements?

Accepted Answer

Introduction / Context: Understanding which gauge applies to internal versus external features is a foundational topic in engineering metrology. A plug gauge, a ring gauge, and a snap gauge are often confused because all of them appear in incoming inspection, shop-floor go/no-go checks, and statistical process control. This question validates the correct mapping between gauge type and part feature—specifically whether a plug gauge can be used to assess the diameter of shafts and studs, which are external (outside) features. Given Data / Assumptions: Shafts and studs present an external cylindrical surface whose size must be verified. Plug gauges are solid cylindrical gauges with GO/NO-GO ends sized for internal features such as holes and bores. Ring and snap gauges are purpose-designed for external diameters. Concept / Approach: By definition, a plug gauge is inserted into a hole to check whether the hole size lies within tolerance (GO end should enter; NO-GO end should not). For external diameters such as shafts, inspectors use ring gauges (GO/NO-GO rings that slip over the outside) or snap gauges/caliper gauges that straddle the part. Therefore, assigning a plug gauge to check shafts or studs is conceptually incorrect. Step-by-Step Solution: 1) Identify the feature to be checked: external cylinder (shaft/stud).2) Recall gauge-function mapping: plug → internal; ring/snap → external.3) Conclude the statement is false; the correct tools are ring or snap gauges, not plug gauges. Verification / Alternative check: Typical inspection work instructions list plug gauges under the section ‘‘hole inspection’’ and ring/snap gauges under ‘‘shaft inspection.’’ Coordinate measuring machines (CMMs) or micrometers may also verify sizes but are not GO/NO-GO gauges. Why Other Options Are Wrong: Correct: contradicts the fundamental internal–external assignment. Correct only for threaded studs: external thread gauges are ring thread gauges, not plug gauges (which are used for internal threads). Correct if a taper plug is used: taper plugs still evaluate sockets/tapered holes internally. Depends on fit class: fit class affects gauge sizes, not the internal/external nature of the gauge. Common Pitfalls: Assuming any cylindrical gauge can assess any cylindrical feature. Confusing ring thread gauges with plug thread gauges due to similar GO/NO-GO logic. Final Answer: Incorrect

Question 19

In foundry sand technology for moulding, the property responsible for allowing the large quantities of steam and other gases (generated during pouring and solidification) to escape through the mould is called what?

Accepted Answer

Introduction / Context: When molten metal enters a sand mould, moisture flashes to steam and binders decompose, releasing gases. If these gases cannot escape, casting defects such as blows, pinholes, and gas porosity arise. The sand property that governs the passage of gases through the body of the mould is a cornerstone of foundry science and quality control. Given Data / Assumptions: Standard green-sand or chemically bonded sand moulds are considered. Gas generation is inevitable due to moisture and binder breakdown. Core and mould vents supplement inherent sand properties. Concept / Approach: Permeability is defined as the ability of the moulding sand to allow gases to pass through it. It depends on grain size/shape, bonding, moisture content, and degree of compaction. High permeability facilitates the escape of steam and decomposition gases, reducing internal pressure and the risk of gas-related defects. Other properties—cohesiveness (bonding strength), adhesiveness (sand-to-flask stick), collapsibility (ability to yield during contraction)—address different performance needs. Step-by-Step Solution: 1) Identify the engineering requirement: gases must escape during pouring and solidification.2) Match requirement to sand property: permeability controls gas flow through the mould body.3) Therefore, the correct term is ‘‘permeability.’’ Verification / Alternative check: Permeability is routinely measured using standard permeability meters (air-flow tests) and specified in process sheets for a given casting and sand system. Why Other Options Are Wrong: Cohesiveness: relates to internal bonding strength, not gas passage. Adhesiveness: describes the tendency of sand to stick to the flask/pattern. Collapsibility: helps avoid hot tears by yielding during contraction, not by venting gases. Green strength: overall strength in moist condition; again not gas flow. Common Pitfalls: Misreading ‘‘evolves gases’’ as a property of sand; the key is the escape of gases through sand (permeability), not their generation. Over-compacting sand, which reduces permeability despite good strength. Final Answer: permeability

Question 20

In oxy-acetylene ‘‘back-hand’’ (rightward) gas welding technique, what range of angles between the welding torch and the workpiece is generally recommended for proper puddle control and penetration?

Accepted Answer

Introduction / Context: Gas welding uses two principal torch manipulations—fore-hand (leftward) and back-hand (rightward). The recommended torch angle is different for each because the direction of heat flow, puddle protection, and filler addition change with technique. Choosing the correct angle range ensures steady molten pool control and proper penetration without excessive oxidation or undercutting. Given Data / Assumptions: Back-hand (rightward) oxy-acetylene welding on mild steel plate of moderate thickness. Neutral flame and standard nozzle selection. Operator maintains normal travel speed. Concept / Approach: In the back-hand technique, the torch points toward the completed weld and heat is directed more into the thicker, already-heated metal, aiding penetration. The commonly recommended torch angle to the work is around 40°–50° for back-hand welding, whereas fore-hand typically uses a lower angle (≈30°–40°). Holding too steep or too shallow an angle affects shielding, puddle support, and bead shape. Step-by-Step Solution: 1) Identify technique: back-hand (rightward) travel with the torch trailing the direction of movement.2) Apply standard practice: set torch inclination in the 40°–50° range.3) Monitor bead and adjust slightly within the range to suit plate thickness and joint design. Verification / Alternative check: Training manuals list 30°–40° for fore-hand and 40°–50° for back-hand as baseline angles, corroborating the recommended values for typical joints. Why Other Options Are Wrong: 30°–40°: more characteristic of fore-hand technique. 50°–60° and 60°–70°: too steep; risk narrow bead and excessive oxidation/undercut. 20°–30°: too shallow; poor puddle coverage and inconsistent penetration. Common Pitfalls: Confusing torch angles between fore-hand and back-hand methods. Overcompensating angle to correct travel speed errors, leading to defects. Final Answer: 40°–50°

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