Question 1

Drilling machine speeds — geometric progression selection A six-speed drilling machine must cover drill diameters from 6.25 mm up to 25 mm at a cutting speed of 18 m/min. Assuming spindle speeds are arranged in a geometric progression to suit this r…

Accepted Answer

Introduction / Context: Machine-tool speed charts are typically laid out in a geometric progression so that a single gearbox covers a wide range of cutting conditions without leaving big gaps. For drilling, spindle speed n is inversely proportional to drill diameter D for a given cutting speed V. This question tests selection of the common ratio for a six-speed drilling machine to span diameters from 6.25 mm to 25 mm at a fixed V. Given Data / Assumptions: Diameter range: Dmin = 6.25 mm, Dmax = 25 mm. Cutting speed: V = 18 m/min (constant across the range). Number of distinct speeds: z = 6, arranged in geometric progression. Formula for drilling: n = V / (pi * D), with consistent units. Concept / Approach: Because n is proportional to 1/D, the ratio of extreme speeds equals the inverse ratio of extreme diameters. With z speeds in geometric progression, nmax = nmin * r^(z−1), where r is the common ratio. Solve for r from the required total range. Step-by-Step Solution: Compute the overall speed range: nmax / nmin = Dmax / Dmin = 25 / 6.25 = 4.Relate to geometric progression: r^(z−1) = r^5 = 4.Solve for r: r = 4^(1/5).Numerical value: 4^(1/5) ≈ 1.3195, which rounds to 1.32. Verification / Alternative check: If r = 1.32, then r^5 ≈ 1.32^5 ≈ 4.00, matching the required 4:1 speed range exactly, so the progression covers 6.25 to 25 mm properly. Why Other Options Are Wrong: 1.02 gives an unrealistically fine progression (r^5 ≈ 1.10). 1.66 and 1.82 produce r^5 far exceeding 4, creating gaps. 1.41 gives r^5 ≈ 5.38, still too large a range. Common Pitfalls: Forgetting that speed varies as 1/D, using linear instead of geometric spacing, or mixing units (mm vs m) when computing absolute n. Here only ratios are needed, so unit consistency is implicit. Final Answer: 1.32

Question 2

Shaper kinematics — average ram speed over full cycle A shaping machine has a stroke length of 250 mm and makes 30 double strokes per minute. Considering both forward and return strokes, what is the overall average speed of ram motion in m/min along…

Accepted Answer

Introduction / Context: In shaping machines, the ram travels the stroke distance during the cutting stroke and the same distance back during the return stroke. Production calculations often need the average linear speed over the full cycle (both strokes) for estimating time and power. This is different from cutting speed (usually based on forward stroke only). Given Data / Assumptions: Stroke length L = 250 mm per single stroke. Cycles = 30 double strokes per minute (each cycle includes one forward and one return stroke). Overall average speed refers to total travel per minute divided by time (1 minute). Concept / Approach: Total distance traveled in one double stroke equals forward distance plus return distance, i.e., 2 * L. The number of double strokes per minute times this distance gives total travel per minute. Convert to meters as needed to express m/min. Step-by-Step Solution: Compute distance per double stroke: s = 2 * L = 2 * 250 mm = 500 mm = 0.5 m.Compute total distance per minute: S = 0.5 m * 30 = 15 m.Overall average speed over the full cycle = 15 m/min. Verification / Alternative check: Dimensional check: stroke (m) * cycles per min yields m/min; numbers are consistent. Even if the return stroke is quicker, the overall average over distance still uses total travel divided by total time, which here is directly given by cycles per minute. Why Other Options Are Wrong: 3.75, 5, and 7.5 m/min would correspond to incorrectly using only half, one-third, or half the number of strokes or stroke length. 10 m/min does not match any logical fraction of the correct calculation. Common Pitfalls: Confusing average cutting speed (forward stroke only) with overall average speed. Here, the question explicitly asks for total motion in both directions. Final Answer: 15 m/min

Question 3

Lathe capacity — relation between swing over bed and swing over carriage In a centre lathe, the swing diameter over the carriage (or cross-slide) compared with the swing diameter over the bed is always:

Accepted Answer

Introduction / Context: “Swing” indicates the largest diameter of work that can rotate without interference. Swing over bed is measured from the lathe bed, while swing over carriage (or cross-slide/compound) reflects the reduced clearance when the tool-holding structures are in place. Understanding this distinction is vital for checking workpiece fit. Given Data / Assumptions: Swing over bed ≥ swing over carriage (cross-slide and compound sit above bed level). Standard centre lathe geometry. No special gap bed or removed top-slide arrangements considered. Concept / Approach: The cross-slide and compound rest occupy vertical space above the bed, reducing available clearance to the rotating job. Therefore, the permissible diameter over the carriage is always less than that over the bed. Step-by-Step Solution: Define swing over bed = 2 * (distance from spindle centre to bed).Define swing over carriage = 2 * (distance from spindle centre to highest obstruction on carriage).Because the carriage sits above the bed, the second distance is smaller; thus swing over carriage is less. Verification / Alternative check: Lathe specification sheets list both values; swing over carriage is consistently smaller. Gap bed lathes may temporarily increase swing near the faceplate, but the general statement remains true. Why Other Options Are Wrong: “No” contradicts geometry. Spindle nose does not set carriage clearance. Equality is not typical, and “greater over carriage” is impossible in standard layout. Common Pitfalls: Confusing special gap or faceplate areas with general swing; mixing “between centres” capacity with swing. Final Answer: Yes

Question 4

Single-point cutting tool geometry — which angles does it possess? A standard single-point cutting tool used on a lathe includes several defined angles. Which of the following does such a tool have as part of its geometry?

Accepted Answer

Introduction / Context: Single-point cutting tool geometry governs chip flow, cutting forces, tool life, and surface finish. Essential angles include rake, clearance, and the resulting wedge (lip) angle, as well as approach and inclination angles depending on the reference system used (ASA/ORS/NRS). Given Data / Assumptions: Standard single-point tool (e.g., for turning). Common reference systems apply. Plain turning of ductile metals. Concept / Approach: Rake angle controls chip flow and cutting energy. Clearance angle prevents rubbing. The cutting (wedge) or lip angle is the included angle between rake and clearance surfaces; it must be sufficient to provide strength. Together, these angles define how the tool penetrates and shears the work material. Step-by-Step Solution: Identify key angles: rake (back and side), clearance (end and side), and included wedge/lip angle.Recognize that “cutting angle” commonly refers to the wedge/lip angle or the approach angle contextually.Conclude a single-point tool possesses rake, cutting (wedge), and lip angles collectively. Verification / Alternative check: Tool angle charts in textbooks and manufacturers’ catalogs list these angles explicitly for standard tool grinds. Why Other Options Are Wrong: Choosing only one angle ignores the interdependence of tool geometry. “None” is clearly incorrect. Common Pitfalls: Confusing approach angle with rake; neglecting that lip/wedge angle is complementary to rake and clearance (lip = 90° − rake − clearance in a simplified 2D view). Final Answer: All of these

Question 5

Capability of a shaper — can it cut keyways, grooves, and slots? Consider the versatility of a standard shaper machine with appropriate tooling and setups. Can keyways, grooves, and slots be produced on a shaper?

Accepted Answer

Introduction / Context: Shapers use a reciprocating ram with a single-point tool to generate flat and contoured surfaces. With proper tool geometry, vises, and clamping, they are capable of much more than simple facing—often used in job shops where flexibility matters. Given Data / Assumptions: Standard shaper with toolholders and indexing/slotting tools. Workholding via vice or clamps with parallels and stops. Keyway/groove geometry achievable with step-over and depth control. Concept / Approach: Keyways, grooves, and slots are made by setting appropriate depth of cut and cross feed while using narrow form tools or slotting tools. Internal keyways in blind or through bores are more suited to a slotter or broach, but external and open-ended features are readily shaped. Step-by-Step Solution: Mount a properly ground form tool with required width.Set stroke length and position to cover the slot length.Apply incremental downfeed to reach full depth while using crossfeed for width control.Finish by light passes to achieve size and finish. Verification / Alternative check: Older shop practice frequently used shapers for keyseating on shafts or making straight-sided slots before widespread CNC milling adoption. Why Other Options Are Wrong: Stating “cannot be cut” is incorrect; while milling or broaching may be faster, shapers can produce these features. Limiting to non-ferrous or only milling ignores tooling versatility. Common Pitfalls: Attempting deep internal keyways without a slotter/broach; inadequate clamping causing chatter; using an overly wide tool causing excessive force. Final Answer: False

Question 6

Chip formation — primary factor promoting discontinuous chips Which cutting condition most strongly favors the formation of discontinuous (segmented) chips during machining of metals?

Accepted Answer

Introduction / Context: Chip type is a direct outcome of material behavior and cutting conditions. Discontinuous chips are desirable with brittle materials but can also occur in ductile materials under unfavorable conditions, affecting surface finish and tool forces. Given Data / Assumptions: General turning of steels for illustration. Tool geometry adjustable (rake angle). Speed can be varied; feed and depth moderate. Concept / Approach: Low speed increases contact time and promotes sticking–slipping at the tool–chip interface. A small rake angle increases deformation and compressive stress ahead of the tool. Together, these raise the tendency for shear localization and crack initiation in the chip, producing segmentation (discontinuous chips). Step-by-Step Solution: Recognize that discontinuous chips arise from cyclic crack initiation along the shear plane.Low speed + small rake raises ploughing and built-up edge, destabilizing flow.Hence, choose the combination that best matches these conditions: low speed and small rake. Verification / Alternative check: Increasing speed and using a larger positive rake typically transitions chip flow toward continuous chips in ductile materials and improves finish. Why Other Options Are Wrong: High speed and large rake favor continuous chips; high speed with small rake still tends to stabilize chip flow more than low speed; low speed with large rake is less prone to segmentation than with small rake. Common Pitfalls: Confusing chip segmentation due to material brittleness with segmentation caused by cutting conditions; ignoring the role of lubrication and temperature. Final Answer: Low cutting speed and small rake angle

Question 7

Jig versus fixture — what uniquely defines a jig? In production tooling, which statement correctly defines a jig as distinct from a fixture?

Accepted Answer

Introduction / Context: Tooling for batch or mass production aims to reduce setup time and ensure repeatable quality. Two common devices are jigs and fixtures. Understanding the difference is crucial for correct process planning. Given Data / Assumptions: Jigs and fixtures provide holding and location. Only jigs include tool guidance elements (e.g., drill bushes). Inspection gauges are a separate category. Concept / Approach: A jig both locates/holds the work and guides the tool (for example, drill jigs use bushes to guide drills). A fixture locates/holds the work but does not guide the tool; e.g., a milling fixture holds the part while the cutter path is controlled by the machine. Step-by-Step Solution: Identify the unique feature: tool guidance.Map to the options: only option (a) includes guidance.Therefore, (a) is the correct definition of a jig. Verification / Alternative check: Industry standards and textbooks consistently define jigs by the presence of tool-guiding elements such as bushes and templates. Why Other Options Are Wrong: (b) defines a fixture (holding/locating only). (c) describes gauges/inspection fixtures, not jigs. (d) cannot be correct since (a), (b), and (c) are mutually exclusive roles. (e) lacks location, which is essential for both jigs and fixtures. Common Pitfalls: Using “jig” and “fixture” interchangeably; forgetting that in modern CNC practice, tool guidance is less necessary for some operations, but the definitions remain. Final Answer: Holds and locates a workpiece and also guides/controls one or more cutting tools

Question 8

Grinding wheel glazing — when does it occur? Glazing is the condition where the wheel surface becomes shiny and stops cutting effectively. Under which conditions is glazing most likely to occur?

Accepted Answer

Introduction / Context: Grinding relies on self-sharpening: dull grains should fracture or pull out to expose fresh cutting edges. When this does not happen, the surface “glazes,” reducing stock removal and increasing heat and burn risk. Given Data / Assumptions: Abrasive type and grade influence grain retention. Peripheral speed affects force per grain and cutting temperature. Work material is steel for illustration. Concept / Approach: A hard-grade wheel holds grains too firmly; dull grains remain, rubbing instead of cutting. Excessive wheel speed raises rubbing action and temperature, further polishing the surface. Both conditions promote glazing. Conversely, a softer grade at appropriate speed allows dull grains to shed, maintaining a sharp wheel face. Step-by-Step Solution: Relate glazing to inadequate grain renewal.Identify causes: hard grade and/or excessively high surface speed.Choose the option that captures these causes. Verification / Alternative check: Dressing removes glazed layers; after dressing, the wheel cuts freely again, confirming that the previous surface was polished/dull rather than sharp. Why Other Options Are Wrong: Soft wheels or very low speeds tend to avoid glazing (but may cause other issues like wheel breakdown). “Hard + very low speed” reduces rubbing per grain; “soft + very high speed” more likely leads to breakdown, not glazing. Coolant flow alone does not cause glazing. Common Pitfalls: Confusing glazing with loading (chip packing). Loading is common on soft gummy materials like aluminum and appears as embedded swarf, not a polished surface. Final Answer: Wheel too hard or wheel speed very high

Question 9

Grinding wheel grade — what does a “hard” wheel mean? A grinding wheel is said to be of which grade if it holds the abrasive grains more securely and releases them less readily during grinding?

Accepted Answer

Introduction / Context: Wheel grade expresses the bond’s holding power on abrasive grains, not the abrasive’s intrinsic hardness. Selecting the right grade is essential to balance self-sharpening and wheel wear. Given Data / Assumptions: Standard vitrified or resinoid-bond wheels. Conventional abrasives (aluminium oxide or silicon carbide). Grinding steels as a representative case. Concept / Approach: A hard-grade wheel firmly retains grains; dull grains remain longer before being shed. This is useful when grinding soft or ductile materials that would otherwise cause rapid wheel wear. Soft-grade wheels release grains sooner, avoiding glazing when grinding hard materials. Step-by-Step Solution: Define grade: bond strength in holding grains.Relate “holds more securely” to “hard grade.”Select the appropriate option. Verification / Alternative check: Manufacturers’ charts correlate recommended grade with workpiece hardness and contact area; harder grades are suggested for softer materials and large contact widths. Why Other Options Are Wrong: Soft/medium grades do not hold grains as securely; “open structure” and “porous” refer to spacing/porosity, not bond holding power (grade). Common Pitfalls: Mixing up “grade” (bond holding) with “grit size” (grain size) or “structure” (spacing between grains). Final Answer: Hard grade

Question 10

Cutting force measurement — what does a machining dynamometer measure? In metal cutting research and shop practice, a dynamometer attached to the tool or workpiece is primarily used to measure:

Accepted Answer

Introduction / Context: Understanding cutting mechanics requires accurate force data. Machining dynamometers quantify the forces acting on the tool/workpiece during cutting, enabling optimization of feeds, speeds, tool geometry, and process stability. Given Data / Assumptions: Dynamometers can be strain-gauge, piezoelectric, or hydraulic type. Forces typically resolved into three orthogonal components (tangential, feed, radial). Applicable to turning, milling, drilling, and grinding variants. Concept / Approach: Cutting force components are fundamental to estimating power (P = Ft * V), tool stresses, chatter tendencies, and specific cutting energy. Dynamometers provide direct measurement, unlike indirect inference from motor load or chip geometry. Step-by-Step Solution: Mount the tool/work on the dynamometer platform.Record force signals during cutting and resolve into components.Use data to compute power, specific energy, and to evaluate tool/work combinations. Verification / Alternative check: Comparing measured tangential force with spindle power and cutting speed gives consistent power estimates, validating readings. Why Other Options Are Wrong: Chip thickness ratio is obtained from chip and feed measurements, not from a dynamometer. Tool wear is measured via microscopy or in-process sensing; deflection can be inferred from force but is not directly measured unless using displacement sensors. Common Pitfalls: Ignoring system stiffness and sensor calibration; misalignment can skew component separation. Final Answer: Forces during metal cutting

Question 11

Drilling practice: The recommended cutting speed for a drill depends on which factors?

Accepted Answer

Introduction / Context: Selecting cutting speed for drilling is a core shop decision that affects tool life, hole accuracy, and productivity. The correct speed is not a single fixed value; it changes with tool material, work material, and the demanded surface finish or tolerance. Given Data / Assumptions: Standard twist drill operation. Choices compare three common influencers: drill material, work material, and finish requirement. Coolant and rigidity are assumed adequate. Concept / Approach: Cutting speed V (m/min) is the surface speed at the drill periphery. It is chosen from machinability tables and adjusted for conditions. HSS, cobalt HSS, and carbide allow different speeds; aluminum, copper, steels, and superalloys require different speeds; finer finish and tighter tolerance often require lower speeds and feeds to control heat and chatter. Step-by-Step Solution: For tool material: Carbide permits higher V than HSS; coated tools may further increase V.For work material: Free-cutting aluminum allows high V; hardened steels require lower V.For surface finish: To reduce chatter/heat and improve Ra, speed and feed are tuned (often lower V or optimized feed).Therefore, speed depends on all listed factors. Verification / Alternative check: Handbooks list ranges by tool and work material; finish notes specify derating for close-tolerance bores and reaming allowances. Why Other Options Are Wrong: Material of the drill only: ignores large differences among work materials and finish needs. Type of work material only: tool capability limits cannot be ignored. Surface finish only: without considering tool/work, finish alone cannot set V. Common Pitfalls: Using one speed for all diameters; remember N = (1000 * V) / (π * D). Larger D needs lower rpm to keep the same surface speed. Final Answer: All of these

Question 12

Non-traditional machining selection: Which process is best for producing parts with large curved surfaces and thin sections?

Accepted Answer

Introduction / Context: Complex aerospace skins, contoured panels, and thin webs require material removal over broad areas with minimal residual stresses or distortion. Traditional chip-removal can warp thin sections. The question tests recognition of the process that excels in thinning large, curved surfaces. Given Data / Assumptions: Large-area, shallow, controlled material removal. Curved or contoured geometry. Thin sections sensitive to mechanical loads and heat. Concept / Approach: Chemical milling (chem-mill) removes material by controlled chemical dissolution using masks to protect regions. It applies uniform etching over large areas, ideal for weight reduction pockets and contoured skins, while imparting negligible machining forces and minimal heat. Step-by-Step Solution: Identify need: large curved surfaces + thin sections → avoid cutting forces.Compare processes: USM and ECM are localized; hot machining is thermal assist to conventional cutting.Chemical milling provides broad-area, low-stress thinning with masking.Hence choose chemical milling. Verification / Alternative check: Industry practice in aerospace (aluminum, titanium) uses chem-mill to create lightening pockets and maintain contour fidelity. Why Other Options Are Wrong: Hot machining: assists hard-to-cut alloys but still uses cutting forces; not ideal for very thin skins. Ultra-sonic machining: best for small features in hard, brittle materials; not efficient for large areas. ECM: precise but equipment/fixturing best suited to localized cavities, blades, or intricate shapes rather than large broad-area thinning. Common Pitfalls: Overlooking masking cost and undercut in chem-mill; process planning must include allowance for etch factor and dimensional control. Final Answer: Chemical milling

Question 13

Lathe workholding: A mandrel is primarily used to hold which type of work for turning the outside accurately?

Accepted Answer

Introduction / Context: Mandrels are arbors inserted into a preformed hole so that the outside surface can be turned truly concentric with that hole. They are widely used when the workpiece is thin or delicate and cannot be gripped rigidly by a chuck without deformation. Given Data / Assumptions: The work already has a through hole or bore. Goal is accurate external turning concentric to that bore. Deformation risk exists if jaws clamp directly on the outside. Concept / Approach: By expanding or driving the mandrel into the bore, the work is supported internally along its length, minimizing distortion. Thin rings, pulleys, and bushings are classic use cases. Step-by-Step Solution: Identify work geometry: thin-walled rings need internal support.Choose mandrel: plain, expanding, or collet-style based on tolerance.Mount between centers or in a collet; turn exterior surfaces true to the bore.Therefore, the most appropriate description is “a thin work”. Verification / Alternative check: Shop manuals list mandrel applications specifically for thin, delicate, or ring-shaped components. Why Other Options Are Wrong: Eccentric work requires special chucks/fixtures; a simple mandrel does not correct eccentricity. Heavy work is often better in a 4-jaw or faceplate with robust support. “None of these” is incorrect because thin ring-like jobs are classic mandrel cases. Common Pitfalls: Using an undersized mandrel leading to slip; proper interference/expansion and end support between centers are essential for accuracy. Final Answer: A thin work

Question 14

Mechanics of drilling: The primary mechanism of metal removal in drilling is

Accepted Answer

Introduction / Context: Drilling combines cutting at the lips with severe deformation at the chisel edge. Understanding both actions explains thrust force, heat, and the need for proper point geometry and feed. Given Data / Assumptions: Standard twist drill with chisel edge and two cutting lips. Homogeneous ductile work material. Normal feeds and speeds. Concept / Approach: At the lips, a conventional shear plane forms and material is cut (shearing). At the chisel edge, there is little true cutting because the local speed approaches zero; material is displaced plastically (extruded) and fractured, contributing to high thrust and heat. Step-by-Step Solution: Recognize dual zones: lips (shearing) and chisel (extrusion/deformation).Resulting chip is produced by both mechanisms, not by shearing alone.Point thinning reduces chisel extrusion, lowering thrust and heat.Hence, the correct choice is “shearing and extrusion”. Verification / Alternative check: Force measurements show large axial thrust attributable to chisel-edge extrusion; split-point drills reduce it noticeably. Why Other Options Are Wrong: Shearing only: ignores the chisel-edge plastic flow. Extrusion only: ignores true cutting action at the lips. Shearing and compression: compression occurs, but the defining non-cutting action is extrusion at the chisel edge. Common Pitfalls: Assuming more speed always fixes poor chip evacuation; geometry at the chisel and proper coolant delivery are just as critical. Final Answer: Shearing and extrusion

Question 15

Machine capacity terminology: A “15 mm drilling machine” can drill a hole of what capacity?

Accepted Answer

Introduction / Context: Manufacturers describe drill presses by a capacity number (e.g., 10 mm, 15 mm, 25 mm). Understanding this nomenclature helps select the correct machine for a job. Given Data / Assumptions: Capacity refers to mild steel drilling capability under standard conditions. Tooling and feeds are appropriate for the rating. Concept / Approach: The capacity designation indicates the largest hole diameter the machine is designed to drill in a typical material (commonly mild steel) with standard tooling, within safe power and rigidity limits. Step-by-Step Solution: Identify what capacity generally means in specs.Translate “15 mm machine” → drills up to 15 mm diameter.Plate thickness or area figures are not part of capacity naming.Therefore, correct interpretation is maximum diameter 15 mm. Verification / Alternative check: Spec sheets show motor power, spindle taper, and “maximum drilling diameter” matching the capacity value. Why Other Options Are Wrong: “In 15 mm thick plates” confuses thickness with diameter capacity. “15 mm^2 area” is unrelated to drilling capacity terminology. “None of these” is incorrect since the standard meaning is well defined. Common Pitfalls: Ignoring that real achievable diameter depends on work material; hard alloys may require derating even if the nominal capacity is 15 mm. Final Answer: Maximum diameter 15 mm

Question 16

Process capability: Ultrasonic machining (USM) is best suited for which type of material/application?

Accepted Answer

Introduction / Context: Ultrasonic machining is a non-thermal, non-electrochemical process that removes material by micro-chipping with abrasive slurry agitated at ultrasonic frequency. It excels on hard, brittle, non-conductive materials. Given Data / Assumptions: Abrasive slurry and vibrating tool at ~20 kHz. Low cutting forces compared to conventional machining. Focus on “best suited” application class. Concept / Approach: USM is particularly effective for brittle materials (glass, ceramics, carbides) where conventional tools would wear rapidly or cause cracking. Among the options, glass is prototypical: hard, brittle, and non-conductive, making USM ideal. While USM also machines sintered carbides, it is not preferred for ductile tool steels. Step-by-Step Solution: Identify target material class: hard and brittle → glass fits perfectly.Consider carbides: also machinable by USM but typically slower and with higher tool wear than EDM/ECM alternatives for some shapes.Tool steels: ductile and better handled by grinding/milling/EDM; USM is not “best”.Therefore, among given choices, “glass” is the best-suited exemplar. Verification / Alternative check: Applications include drilling glass, ceramics, sapphire, and ferrites with minimal edge chipping compared to conventional drilling. Why Other Options Are Wrong: Tool steels: USM is inefficient; conventional or EDM are better. Sintered carbides: machinable, but “best suited” highlights classic non-conductive brittle materials such as glass. All of these: incorrect because USM is not best for ductile tool steels. Common Pitfalls: Confusing the broad capability with best suitability; “best” refers to the class where USM clearly outperforms traditional cutting. Final Answer: Glass

Question 17

Chip control: What is the primary purpose of a chip breaker on a cutting tool?

Accepted Answer

Introduction / Context: Long, stringy chips from ductile materials can entangle the tool or workpiece, damage the surface, and pose safety hazards. Chip breakers are a routine feature of inserts and ground tools to manage chip flow. Given Data / Assumptions: Ductile work material tending to form continuous chips. Typical grooved or formed chip breaker geometry on the rake face. Normal cutting speeds/feeds. Concept / Approach: Chip breakers induce controlled bending and strain in the emerging chip, causing it to curl tightly and fracture into short segments. This improves evacuation, reduces scratching of the finished surface, and prevents chip snarls. Step-by-Step Solution: Design: a step or groove on the rake face forces chip to curl.Chip curvature increases strain → chip fractures into manageable pieces.Result: safer operation and more consistent surface finish.Hence, the key purpose is to break chips into short segments. Verification / Alternative check: Observing chip shape with and without chip breaker quickly confirms the effect; machine interiors stay clearer with segmented chips. Why Other Options Are Wrong: Increase tool life directly: any life improvement is indirect via better chip control and lower rubbing—chip breaker's main role is not life extension. Remove chips from bed: that is the job of conveyors/coolant flow; breakers only create short chips. Minimise heat generation: geometry mainly affects chip control; heat depends on cutting parameters and tool-work chemistry. Common Pitfalls: Using insufficient feed so the chip does not engage the breaker; chip breakers require appropriate feed to function properly. Final Answer: Break the chips into short segments

Question 18

Grinding wheel behaviour: A wheel becomes “glazed” (glass-like cutting edge appearance) primarily due to

Accepted Answer

Introduction / Context: Grinding performance depends on the interplay between abrasive grains and bond. When the abrasive tips dull but do not dislodge, the wheel “glazes,” rubbing instead of cutting, raising heat and harming finish. Given Data / Assumptions: Conventional vitrified or resinoid bonded wheel. Work material causing dulling without sufficient self-sharpening. No recent dressing operation. Concept / Approach: Glazing occurs when cutting points flatten (wear) and the bond is too strong to release them. The wheel surface becomes shiny and slides on the work, increasing power draw and burning risk. Dressing restores sharpness by fracturing grains and exposing new edges. Step-by-Step Solution: Abrasive tips dull → chip thickness drops → sliding increases.Bond retains dull grains → self-sharpening fails → glazing.Correct by dressing or selecting a softer grade so dull grains shed.Therefore, glazing is due to wear (dulling) of abrasive grains. Verification / Alternative check: Power and temperature rise during glazing; dressing restores normal amperage and chip formation. Why Other Options Are Wrong: Wear of bond: would cause wheel to act too soft, not glazed. Breaking of grains: produces fresh sharp edges—opposite of glazing. Cracks: a safety issue but not the mechanism for glazing. Common Pitfalls: Blaming only speed; while speed matters, incorrect grade and infrequent dressing are common root causes. Final Answer: Wear (dulling) of abrasive grains

Question 19

Boring machine kinematics: In which machine does the work remain stationary while the tool rotates during boring?

Accepted Answer

Introduction / Context: Boring enlarges and finishes existing holes. Depending on machine type, either the work rotates (as in vertical turning/boring mills) or the tool rotates while the work stays stationary (as in jig and many horizontal boring machines). The question asks for the machine that clearly uses a rotating tool with a stationary workpiece for precision boring. Given Data / Assumptions: Typical industrial configurations are considered. “Work remains stationary” means it does not rotate; linear feeds may still occur. Precision boring emphasizes positional accuracy and hole quality. Concept / Approach: Jig boring machines are designed for high positional accuracy using precise leadscrews/measurement systems. The spindle with the boring tool rotates; the work is clamped to a coordinate table (non-rotating). This matches the condition in the question most unambiguously. Step-by-Step Solution: Identify machine where work is clamped and non-rotating → jig borer.Tool rotation provides cutting speed; table feeds supply the feed motion.Therefore, select “Jig boring machine”.Note: many horizontal boring machines also rotate the tool with stationary work, but jig boring is the precision-specific answer. Verification / Alternative check: Machine catalogs show jig borers with precision coordinate tables; VBM specs show rotating tables carrying the work. Why Other Options Are Wrong: Vertical boring machine: work rotates on a large table. Horizontal boring machine: often the tool rotates, but configurations vary; the question seeks the precision case—jig borer. Precision boring machine: generic term; jig borer is the specific, standard answer. Common Pitfalls: Assuming “stationary” excludes linear feeds; here it means no rotation of the work. Final Answer: Jig boring machine

Question 20

Grinding wheel grade identification: Letters I to P on a wheel indicate it is of hard grade. Is this statement correct?

Accepted Answer

Introduction / Context: Grinding wheel grade indicates the bond's holding strength of abrasive grains, not the abrasive hardness. Manufacturers encode grade with letters from “A” (very soft) to “Z” (very hard). Understanding this scale helps select a wheel that self-sharpens properly for the job. Given Data / Assumptions: Letter range A–Z increases with grade hardness. Typical convention used in most standards. Statement claims I–P equals “hard grade”. Concept / Approach: Grades I through P correspond to roughly the medium range. Hard grades are typically toward the upper end (e.g., R, S, T … Z). Therefore, stating that I–P is “hard grade” is inaccurate; it is more appropriate to call it “medium”. Step-by-Step Solution: Recall A→Z scale where letter increases with grade hardness.Locate I–P in the middle of the scale → medium holding power.Hard grades are letters beyond roughly P/Q toward Z.Hence, the statement is false. Verification / Alternative check: Wheel markings (e.g., 38A 60 K 5 V) show K as a medium grade letter, reinforcing the mid-range classification. Why Other Options Are Wrong: “True” would mislead users into selecting a wheel that may not shed dull grains, causing glazing. Common Pitfalls: Confusing abrasive grit hardness with grade; grit hardness relates to abrasive type (Al2O3, SiC), while grade refers to bond holding strength. Final Answer: False

Production Engineering Questions