Q: Twist drills – local cutting speed along the lip: Does the cutting speed remain the same from the drill centre to the periphery?

Introduction / Context: Cutting speed in drilling refers to the surface speed at the cutting edge. Because a drill rotates, the local linear speed depends on radius. Understanding this variation explains chip formation and wear patterns (e.g., higher wear at the outer corners). Given Data / Assumptions: Twist drill of diameter D rotating at N r/min. Uniform angular speed for the whole tool. Conventional geometry and feeds. Concept / Approach: Linear speed V at a point equals ω * r. At the centre (r = 0), V = 0, so material removal at the chisel edge involves extrusion rather than true cutting. At the periphery (r = D/2), V is maximum. Therefore, cutting speed does not remain the same along the lip. Step-by-Step Solution: Angular speed ω = 2πN/60.Local speed V(r) = ω * r → increases with radius.At r = 0 (chisel), V = 0; at r = D/2, V = maximum.Thus, the statement “cutting speed is the same” is incorrect. Verification / Alternative check: Examine chips: little true cutting at the centre, thicker chips near the corners; wear is heavier at outer edges where speed is highest. Why Other Options Are Wrong: “Correct” would imply uniform linear speed, which contradicts rotational kinematics. Common Pitfalls: Setting speed based only on material without considering diameter; larger drills require lower rpm to keep peripheral speed within limits. Final Answer: Incorrect

Q: Chip thickness and force in up milling (conventional): How does the cutting force vary per tooth engagement during one pass?

Introduction / Context: Up milling (conventional) feeds the work opposite to the cutter rotation at the contact zone. This determines the chip thickness variation and therefore the instantaneous cutting force on each tooth. Given Data / Assumptions: Peripheral milling with steady feed and depth of cut. Negligible runout and uniform tooth spacing. Homogeneous work material. Concept / Approach: In up milling, the chip thickness starts nearly zero at entry and increases to a maximum at exit. Cutting force is approximately proportional to instantaneous chip load; thus, force grows from near zero to a peak as the tooth traverses the arc of contact. Step-by-Step Solution: Define chip thickness h(θ) in up milling → increases with angular immersion.Force F ∝ h(θ) * width of cut → increases over the tooth path.Therefore, per tooth, force rises from zero at entry to maximum at exit.Contrast with climb milling where chip starts thick and thins to zero. Verification / Alternative check: Force dynamometer traces exhibit a rising sawtooth pattern in up milling, matching the increasing chip thickness. Why Other Options Are Wrong: “Maximum throughout” and “zero throughout” contradict measured force signals; “decreases from maximum to zero” is the pattern for climb milling, not up milling. Common Pitfalls: Mislabeling up vs. down milling when interpreting surface finish and fixture load; always relate force evolution to chip thickness trend. Final Answer: Increases from zero to maximum

Q: Comparative process speeds: With equally rigid machines and identical tool–work materials, which operation is normally run at the lowest cutting velocity?

Introduction / Context: Cutting velocity limits are set by tool material, heat dissipation, tool geometry, and system rigidity. Among common processes, practical speeds differ even for the same material because of tool overhang, engagement style, and stability. Given Data / Assumptions: Machines are equally rigid overall (but tool setups differ). Same tool–work material pairing across processes. Typical production conditions (no special coatings or ceramics). Concept / Approach: Grinding generally uses the highest surface speeds due to abrasive hot hardness. Milling also permits relatively high speeds with intermittent cutting and efficient chip evacuation. Turning speeds are moderate and can be high with carbide. Boring uses a long, slender bar (overhang), reducing dynamic stiffness and increasing chatter risk; thus, boring commonly runs at lower speeds than an equivalent external turning job to maintain stability and surface finish. Step-by-Step Solution: List typical hierarchy: Grinding > Milling ≈ Turning > Boring.Reason: boring bars have lower stiffness (deflection ∝ length^3 / diameter^4 for a cantilever).Lower speed reduces vibration and heat at the tool tip, improving finish and accuracy in deep holes.Hence, boring is usually operated at the minimum cutting velocity among the options. Verification / Alternative check: Shop guidelines often specify speed reductions (and feed adjustments) for internal turning/boring versus external turning on the same work material and insert. Why Other Options Are Wrong: Grinding: typically the highest surface speeds (tens of m/s). Milling: intermittent cutting permits relatively high permissible speeds. Turning: external turning allows higher speeds than boring for the same tool system. Common Pitfalls: Equating machine nameplate rigidity with setup rigidity; boring bar dynamics often govern allowable speed regardless of base machine stiffness. Final Answer: Boring

Question 1

Metal cutting data – drilling copper with HSS: What is the recommended range of cutting speed (surface speed) when drilling copper using high-speed steel (HSS) drills?

Accepted Answer

Introduction / Context: Copper is a relatively soft, thermally conductive metal. When drilling copper with high-speed steel (HSS) drills, shops select a cutting (surface) speed that balances tool life, heat generation, chip control, and productivity. This question checks recall of the typical cutting speed band for HSS drills on copper. Given Data / Assumptions: Tool material: high-speed steel (not carbide or coated carbide). Work material: copper or copper-rich alloy of good machinability. Normal shop conditions with suitable coolant and standard drill geometry. Concept / Approach: Cutting speed V is the surface speed at the drill's outer diameter. For HSS on free-machining nonferrous metals, recommended speeds are higher than for steels due to lower cutting resistance and good heat conduction. Typical handbooks show copper with HSS at roughly 60–90 m/min as a practical range. Step-by-Step Solution: Identify correct band for HSS on copper → high relative to steels.Rule of thumb: V ≈ 60–90 m/min for many coppers with HSS.Set spindle speed N from V = 1000 * V / (π * D) for drill diameter D in mm.Adjust down for gummy grades or poor rigidity; adjust up for free-cutting brasses (with appropriate geometry). Verification / Alternative check: Comparing with speed tables shows 60–90 m/min commonly listed for HSS on copper; lower choices like 10–45 m/min are typical for carbon steels or tougher alloys, not copper. Why Other Options Are Wrong: 10–20 m/min: far too slow for copper with HSS; wastes productivity. 18–30 m/min: still slow; used more for hard steels with HCS tools. 24–45 m/min: moderate for steels; below optimal for copper. Common Pitfalls: Confusing speeds for HSS versus carbide; copper can also grab, so keep drill lip relief moderate and use proper coolant despite the higher speed. Final Answer: 60 to 90 m/min

Question 2

Milling practice – why choose climb (down) milling? Select the principal advantage that motivates choosing climb milling in suitable setups.

Accepted Answer

Introduction / Context: Climb milling (down milling) feeds the work in the same direction as cutter rotation at the contact zone. It changes chip thickness progression and cutting forces compared with conventional (up) milling. The question targets the main shop-floor benefit. Given Data / Assumptions: Backlash is controlled (CNC or anti-backlash gears/ball screws). Work and fixturing are rigid enough for down milling. Comparable conditions otherwise (tool, material, width of cut). Concept / Approach: In climb milling, chip thickness starts at maximum and falls to nearly zero. This reduces rubbing at entry, often lowers specific cutting energy, and leaves a burnished exit surface. The dominant, widely cited practical reason is superior surface finish on many ductile materials under proper rigidity. Step-by-Step Solution: Compare chip formation: climb → max-to-zero, conventional → zero-to-max.Rubbing is reduced at entry in climb → improved finish.Force direction pushes the work into the table → less chatter with rigid setups.Thus the primary benefit chosen is improved surface finish. Verification / Alternative check: Surface roughness measurements (Ra) commonly show better values with climb milling on stiff machines and well-clamped parts. Why Other Options Are Wrong: Chip thickness increases gradually: that describes up milling, not climb. Enables cutter to dig in: this is a drawback (risk of pull-in), not a benefit. Specific power may reduce, but finish is the main, most consistent advantage; the prompt asks for the key reason. Common Pitfalls: Using climb milling on machines with backlash can cause self-feeding; always confirm screw condition and clamp securely. Final Answer: Better surface finish can be obtained

Question 3

Chip formation fundamentals: High cutting speed and a large rake angle generally promote which chip type in ductile materials?

Accepted Answer

Introduction / Context: Chip type affects tool wear, surface finish, and process stability. Tool geometry and cutting parameters steer whether the chip is continuous, segmented, or discontinuous. The question focuses on the effect of high cutting speed and large rake angle. Given Data / Assumptions: Ductile work metal (e.g., low-carbon steel, aluminum). Sharp tool with a relatively large positive rake angle. Sufficient cutting speed to suppress built-up edge formation. Concept / Approach: Large rake reduces shear deformation and cutting forces, while higher speed raises temperature at the shear plane, both encouraging smooth chip flow. These conditions usually suppress built-up edge and promote long, continuous chips in ductile materials. Step-by-Step Solution: Increase rake angle → lower shear strain → smoother flow.Increase speed → higher interface temperature → less adhesion → reduced built-up edge.Combined effect → stable shear plane and continuous chip formation.Therefore, the expected chip type is continuous. Verification / Alternative check: Visual observation and chip morphology under these settings typically show ribbon-like continuous chips with good surface finishes. Why Other Options Are Wrong: Discontinuous chips arise with brittle materials, low rake, or interrupted/low-speed cutting. Continuous with built-up edge is more likely at moderate/low speeds or poor lubrication. “None of these” conflicts with standard metal cutting behavior. Common Pitfalls: Assuming continuous chips are always desirable; they can entangle tools—chip breakers or peck cycles may still be needed. Final Answer: Continuous chips

Question 4

Gear finishing processes: What is gear burnishing primarily used for in manufacturing practice?

Accepted Answer

Introduction / Context: After gear tooth generation (hobbing, shaping), finishing processes improve surface texture, contact pattern, and noise performance. Burnishing is a chip-less cold working technique performed with hardened gear-like tools. Given Data / Assumptions: Process occurs after basic tooth form exists. Burnishing tools are harder than the work gear and roll in mesh. No abrasive is used; the method relies on plastic deformation at asperities. Concept / Approach: Burnishing smooths the flanks by plastically deforming surface peaks into valleys, reducing roughness, improving bearing area, and sometimes inducing beneficial compressive stresses near the surface for better pitting resistance. Step-by-Step Solution: Mount the gear and burnishing tool; mesh under controlled pressure.As they roll, localized yielding flattens asperities → lower Ra.Contact pattern improves; running-in is effectively performed off-line.Result: enhanced surface finish and reduced noise during service. Verification / Alternative check: Surface measurements before/after show reduced roughness; tooth contact analysis indicates improved pattern and load distribution. Why Other Options Are Wrong: Under-cut gears and cycloidal gears describe geometry, not a finishing process. Residual stress removal is linked to thermal stress relief; burnishing typically adds near-surface compressive stress rather than removing it. Common Pitfalls: Confusing burnishing with lapping or honing (abrasive methods). Burnishing is chip-less and relies on plastic flow. Final Answer: Surface finishing

Question 5

Heat partition in continuous chip cutting: The amount of maximum heat generated in cutting primarily __________ the cutting velocity.

Accepted Answer

Introduction / Context: During metal cutting, mechanical work converts to heat in the shear zone and at the tool–chip interface. Cutting velocity strongly influences heat generation rate and the share carried by the chip. The question asks whether the maximum heat depends on cutting speed. Given Data / Assumptions: Continuous chip formation in ductile metals. Comparable feed and depth of cut. Similar tooling and coolant conditions. Concept / Approach: Total heat Q per unit time is roughly proportional to cutting power (force * velocity). Increasing cutting speed, for a given force level, raises power and thus heat generation rate. Although forces can decrease somewhat with speed due to thermal softening, overall heat rate generally rises with speed, and the fraction carried away by the chip also increases. Step-by-Step Solution: Cutting power P ≈ Fc * V (Fc = cutting force; V = speed).Heat rate Q̇ ≈ P (neglecting small elastic storage).As V increases, Q̇ increases; chip temperature and heat fraction to chip rise.Therefore, maximum heat in the process depends on cutting velocity. Verification / Alternative check: Dynamometer and thermocouple studies show tool–chip interface temperatures and chip exit temperatures increase with speed for constant geometry and feed, confirming speed dependence. Why Other Options Are Wrong: Claiming “does not depend” contradicts the direct role of velocity in power; only in narrow regimes with dramatic force drop could heat rate plateau, which is not the general case. Common Pitfalls: Confusing heat fraction (distribution among chip/tool/work) with absolute heat rate; both are influenced by speed but in different ways. Final Answer: depends upon

Question 6

Grinding – process classification: Grinding is primarily considered which type of manufacturing operation?

Accepted Answer

Introduction / Context: Grinding removes small amounts of material using bonded abrasives with many cutting points. It is widely used to produce tight tolerances and fine surface finish on hardened or difficult materials. The question asks for its principal classification. Given Data / Assumptions: Conventional precision grinding (surface, cylindrical, tool-and-cutter). Focus on typical shop practice rather than rough snagging. Abrasive wheels periodically dressed to restore sharpness. Concept / Approach: Although grinding certainly shapes parts, its defining role in precision manufacturing is achieving the final size and finish after prior stock removal operations. Hence it is classed primarily as a surface finishing (or finishing) operation, especially compared to turning, milling, and shaping that remove larger stock. Step-by-Step Solution: Recognize grinding’s fine chip thickness, high accuracy, and low MRR.Typical outcomes: fine Ra values, tight cylindricity/flatness.Therefore, its primary classification is a finishing process.Note: dressing is a maintenance action for wheels, not the workpart process itself. Verification / Alternative check: Process plans place grinding at the end of routing for high-precision components (shafts, bearing seats, gauges), underscoring its finishing role. Why Other Options Are Wrong: Shaping/forming are broader categories; grinding is used after those to refine size/finish. Dressing is done on the wheel to restore cutting ability, not the work operation classification. Common Pitfalls: Assuming grinding only finishes; creep-feed grinding can remove significant stock, but the mainstream view is finishing. Final Answer: Surface finishing operation

Question 7

Drill geometry for brass: The preferred helix angle of a twist drill for drilling brass should be

Accepted Answer

Introduction / Context: Free-cutting brasses are prone to grabbing if aggressive rake/helix geometry is used. Drill design for brass typically differs from that for steels or aluminum to prevent self-feeding and chatter. Given Data / Assumptions: Work: brass or brass-like copper alloy. Tool: standard twist drill with modifiable helix and lip geometry. Goal: stable cutting without grabbing. Concept / Approach: To minimize grabbing in brass, use a lower helix angle and smaller effective rake (even zero/negative rake at the cutting lips by dub-off). A helix less than the common 30° (e.g., 20–25°) reduces the tendency of the tool to pull itself into the work and improves control of chip flow for short, brittle chips typical of free-machining brasses. Step-by-Step Solution: Standard twist drills: ~30° helix for steels.For brass: reduce helix angle < 30° and dub the lip to reduce rake.Result: less self-feeding, smoother entry, reduced chatter.Hence, the correct choice is “less than 30°”. Verification / Alternative check: Tool catalogs and shop practices recommend low-helix, low-rake drills for brass to avoid sudden dig-in. Why Other Options Are Wrong: 30° or more than 30° increase the rake/helix and the risk of grabbing; the question seeks the specific adaptation for brass. Common Pitfalls: Applying high-helix aluminum drills to brass; the geometry suited for long ductile chips can be hazardous on short-chipping brass. Final Answer: Less than 30°

Question 8

Twist drills – local cutting speed along the lip: Does the cutting speed remain the same from the drill centre to the periphery?

Accepted Answer

Introduction / Context: Cutting speed in drilling refers to the surface speed at the cutting edge. Because a drill rotates, the local linear speed depends on radius. Understanding this variation explains chip formation and wear patterns (e.g., higher wear at the outer corners). Given Data / Assumptions: Twist drill of diameter D rotating at N r/min. Uniform angular speed for the whole tool. Conventional geometry and feeds. Concept / Approach: Linear speed V at a point equals ω * r. At the centre (r = 0), V = 0, so material removal at the chisel edge involves extrusion rather than true cutting. At the periphery (r = D/2), V is maximum. Therefore, cutting speed does not remain the same along the lip. Step-by-Step Solution: Angular speed ω = 2πN/60.Local speed V(r) = ω * r → increases with radius.At r = 0 (chisel), V = 0; at r = D/2, V = maximum.Thus, the statement “cutting speed is the same” is incorrect. Verification / Alternative check: Examine chips: little true cutting at the centre, thicker chips near the corners; wear is heavier at outer edges where speed is highest. Why Other Options Are Wrong: “Correct” would imply uniform linear speed, which contradicts rotational kinematics. Common Pitfalls: Setting speed based only on material without considering diameter; larger drills require lower rpm to keep peripheral speed within limits. Final Answer: Incorrect

Question 9

Chip thickness and force in up milling (conventional): How does the cutting force vary per tooth engagement during one pass?

Accepted Answer

Introduction / Context: Up milling (conventional) feeds the work opposite to the cutter rotation at the contact zone. This determines the chip thickness variation and therefore the instantaneous cutting force on each tooth. Given Data / Assumptions: Peripheral milling with steady feed and depth of cut. Negligible runout and uniform tooth spacing. Homogeneous work material. Concept / Approach: In up milling, the chip thickness starts nearly zero at entry and increases to a maximum at exit. Cutting force is approximately proportional to instantaneous chip load; thus, force grows from near zero to a peak as the tooth traverses the arc of contact. Step-by-Step Solution: Define chip thickness h(θ) in up milling → increases with angular immersion.Force F ∝ h(θ) * width of cut → increases over the tooth path.Therefore, per tooth, force rises from zero at entry to maximum at exit.Contrast with climb milling where chip starts thick and thins to zero. Verification / Alternative check: Force dynamometer traces exhibit a rising sawtooth pattern in up milling, matching the increasing chip thickness. Why Other Options Are Wrong: “Maximum throughout” and “zero throughout” contradict measured force signals; “decreases from maximum to zero” is the pattern for climb milling, not up milling. Common Pitfalls: Mislabeling up vs. down milling when interpreting surface finish and fixture load; always relate force evolution to chip thickness trend. Final Answer: Increases from zero to maximum

Question 10

Comparative process speeds: With equally rigid machines and identical tool–work materials, which operation is normally run at the lowest cutting velocity?

Accepted Answer

Introduction / Context: Cutting velocity limits are set by tool material, heat dissipation, tool geometry, and system rigidity. Among common processes, practical speeds differ even for the same material because of tool overhang, engagement style, and stability. Given Data / Assumptions: Machines are equally rigid overall (but tool setups differ). Same tool–work material pairing across processes. Typical production conditions (no special coatings or ceramics). Concept / Approach: Grinding generally uses the highest surface speeds due to abrasive hot hardness. Milling also permits relatively high speeds with intermittent cutting and efficient chip evacuation. Turning speeds are moderate and can be high with carbide. Boring uses a long, slender bar (overhang), reducing dynamic stiffness and increasing chatter risk; thus, boring commonly runs at lower speeds than an equivalent external turning job to maintain stability and surface finish. Step-by-Step Solution: List typical hierarchy: Grinding > Milling ≈ Turning > Boring.Reason: boring bars have lower stiffness (deflection ∝ length^3 / diameter^4 for a cantilever).Lower speed reduces vibration and heat at the tool tip, improving finish and accuracy in deep holes.Hence, boring is usually operated at the minimum cutting velocity among the options. Verification / Alternative check: Shop guidelines often specify speed reductions (and feed adjustments) for internal turning/boring versus external turning on the same work material and insert. Why Other Options Are Wrong: Grinding: typically the highest surface speeds (tens of m/s). Milling: intermittent cutting permits relatively high permissible speeds. Turning: external turning allows higher speeds than boring for the same tool system. Common Pitfalls: Equating machine nameplate rigidity with setup rigidity; boring bar dynamics often govern allowable speed regardless of base machine stiffness. Final Answer: Boring

Question 11

Broaching tool design In a standard push or pull broach used for internal or surface broaching, how does the height of successive teeth vary along the tool length?

Accepted Answer

Introduction / Context: Broaching is a high-production machining process that uses a multi-tooth tool to remove metal in a single pass. Understanding tooth geometry—especially how tooth height changes along the broach—is fundamental to why broaching achieves accuracy, surface finish, and short cycle time. Given Data / Assumptions: The tool is a conventional broach (internal or surface type). Each tooth removes a small layer of material called rise per tooth. The broach carries roughing, semi-finishing, and finishing teeth in one tool. Concept / Approach: The tooth height must increase progressively so that each subsequent tooth removes slightly more depth than the previous one until the final geometry is reached. After roughing teeth, semi-finishing teeth reduce scallops, and finishing teeth (often with equal height) refine size and surface finish. Step-by-Step Solution: Recognize that broaching removes metal in many small increments, not one large cut.Therefore, successive teeth must be higher than the previous tooth by rise per tooth to engage fresh material.The finishing section often has equal-height teeth to burnish and size, but the general rule along the cutting section is progressive increase. Verification / Alternative check: Shop practice and tool catalogs specify a defined rise per tooth (for example, 0.02–0.08 mm per tooth depending on material), confirming progressive increase through roughing and semi-finishing sections. Why Other Options Are Wrong: Same throughout: would not remove material progressively; only the first tooth would cut.Progressively decreasing: later teeth would not engage; cutting would cease prematurely.None of these / exceptions: while finishing teeth may be equal, the general cutting section increases progressively. Common Pitfalls: Confusing the finishing section (equal height) with the entire broach. The question concerns the overall cutting principle, not just the last few teeth. Final Answer: In progressively increasing order

Question 12

Tool materials — red hardness of HSS High-speed steel (HSS) cutting tools are known to retain useful hardness up to approximately what temperature under cutting conditions?

Accepted Answer

Introduction / Context: Red hardness (hot hardness) indicates a tool material’s ability to retain hardness, and therefore cutting ability, at elevated temperatures generated during machining. HSS became a breakthrough because it maintains useful hardness significantly above that of plain carbon tool steels. Given Data / Assumptions: Conventional HSS grades (e.g., M2, T1) under typical cutting conditions. No advanced coatings or high-pressure coolant assumed. Comparison with much higher hot hardness of carbides and ceramics. Concept / Approach: Carbon tool steels rapidly lose hardness above roughly 200–250°C. HSS remains serviceable to temperatures around the 500–600°C range, enabling higher cutting speeds than carbon steel tools. Carbides and ceramics extend this much further. Step-by-Step Solution: Identify approximate temperature where HSS retains cutting hardness → about 500–600°C.Compare to options: 500°C is the correct representative value among the choices.Reject extremes (250°C too low; 900°C too high for HSS; 350°C still low for HSS capability). Verification / Alternative check: Textbook data cites HSS operational hot hardness range near 550°C; 500°C is a standard rounded figure for exam contexts. Why Other Options Are Wrong: 250°C / 350°C: more indicative of carbon tool steels; underestimate HSS performance.900°C: closer to carbide/ceramic realms; unrealistic for HSS. Common Pitfalls: Assuming HSS equals carbide performance; in reality carbides operate far hotter with superior wear resistance, enabling much higher speeds. Final Answer: 500°C

Question 13

Hot machining preference In hot machining (workpiece locally heated before cutting), solid carbide tools are preferred over high-speed steel tools. Is this statement correct?

Accepted Answer

Introduction / Context: Hot machining preheats the workpiece to lower its flow stress, reducing cutting forces and improving machinability of hard or heat-resistant alloys. Tool material selection remains critical because the tool still experiences elevated temperatures. Given Data / Assumptions: Workpiece is locally preheated (flame, induction, laser). Elevated cutting temperatures are expected at the tool–chip interface. Comparison between HSS and cemented carbide tools. Concept / Approach: Cemented carbides possess much higher hot hardness and better wear resistance than HSS. In hot machining, where temperatures are intentionally higher, carbide’s ability to retain hardness and resist diffusion/adhesive wear outperforms HSS, which softens significantly above about 500–600°C. Step-by-Step Solution: Recognize hot machining increases interface temperature.Carbide retains hardness and edge integrity at higher temperatures than HSS.Therefore, carbide tools are preferred → the statement is True. Verification / Alternative check: Process guidelines for machining hard steels or superalloys recommend carbides, cermets, ceramics, or PCBN rather than HSS, especially when preheating is used. Why Other Options Are Wrong: Claims that HSS is better ignore its lower hot hardness and faster softening. Limiting to plastics or low speeds misunderstands the purpose of hot machining. Common Pitfalls: Overheating the tool due to excessive preheat; even carbides have limits. Use proper cutting speeds, coolant strategy (often restricted to avoid thermal shock for some tool materials), and stable fixturing. Final Answer: True

Question 14

Ultrasonic machining (USM) — abrasive slurry selection In ultrasonic machining, the abrasive slurry typically contains fine particles of which materials?

Accepted Answer

Introduction / Context: Ultrasonic machining removes material by micro-chipping and erosion using high-frequency tool vibration in the presence of an abrasive slurry. Slurry selection affects material removal rate, surface finish, and tool wear. Given Data / Assumptions: USM applied to hard, brittle materials (glass, ceramics, carbides). Aqueous slurry is used with suspended abrasive particles. Tool vibrates typically at 20–40 kHz with small amplitudes. Concept / Approach: Common abrasives in USM are Al2O3, SiC, and B4C. Particle size selection balances cutting aggressiveness and finish. Diamond can be used but is costlier and may be reserved for special applications. Step-by-Step Solution: Identify standard USM abrasives → Al2O3, SiC, B4C.Since the question asks which are used, the inclusive correct choice is “any one of these.”Diamond is not mandatory and is less common due to cost. Verification / Alternative check: Process handbooks cite Al2O3 and SiC as the most common; B4C is preferred for very hard materials due to higher hardness. Why Other Options Are Wrong: Choosing only one material ignores the range of workable abrasives; diamond-only is too restrictive and uneconomical for general USM. Common Pitfalls: Using particles too fine may slow removal; too coarse may mar the surface. Proper concentration and circulation are also critical. Final Answer: Any one of these

Question 15

Workholding on the lathe For setting up heavy, irregularly shaped workpieces on a lathe, which chuck is most appropriate?

Accepted Answer

Introduction / Context: Workholding determines accuracy, safety, and flexibility on a lathe. Irregular or off-center parts require independent adjustment of jaws to achieve secure clamping and precise centering or intentional eccentricity. Given Data / Assumptions: Workpiece is heavy and irregular in geometry. Need independent jaw adjustment for balancing and centering. Operation on engine lathe with standard chucks available. Concept / Approach: A four-jaw independent chuck allows each jaw to be adjusted separately to grip uneven shapes, castings, or forgings. It also enables deliberate offset turning. A three-jaw self-centering chuck is faster but suited to regular round or hex stock. Step-by-Step Solution: Identify work irregularity and weight → requires independent jaw control and strong clamping.Select four-jaw independent chuck.Verify suitability: dial-indicator centering is possible; clamping forces are high. Verification / Alternative check: Workshop practice universally recommends four-jaw independents for irregular shapes and non-concentric setups. Why Other Options Are Wrong: Three-jaw universal: quick but limited to symmetric stock; can’t independently adjust jaws. Magnetic and drill chucks are unsuitable for heavy irregular lathe work. Collets demand precise round stock and limited diameters. Common Pitfalls: Attempting to force fit irregular pieces in a three-jaw; this leads to poor grip, runout, and safety hazards. Final Answer: Four-jaw independent chuck

Question 16

Improving surface finish in turning Which changes generally improve surface finish, assuming stable setup and appropriate tool material?

Accepted Answer

Introduction / Context: Surface finish results from the interplay of tool geometry, cutting parameters, machine stiffness, and material behavior. Certain parameter changes consistently reduce feed marks and improve the machined texture when other conditions are controlled. Given Data / Assumptions: Stable workholding and machine condition (no chatter). Proper tool material for the workpiece. Reasonable feeds and depths for finishing. Concept / Approach: Higher cutting speed often improves finish by reducing built-up edge. A larger tool nose radius blends feed marks, producing a smoother surface, though it may increase cutting forces. A more positive rake promotes shearing over ploughing, reducing forces and improving flow of chips. Step-by-Step Solution: Evaluate effect of speed: increased speed diminishes built-up edge → better finish.Evaluate nose radius: larger radius reduces cusp height from feed → smoother finish.Evaluate rake: more positive rake lowers cutting forces and rubbing → better finish. Verification / Alternative check: Surface-roughness models relate cusp height to feed and nose radius; tribological data tie built-up edge to speed and rake. Why Other Options Are Wrong: Choosing any single factor ignores the combined benefit. The distractor advocating lower speed and negative rake typically worsens finish due to BUE and rubbing. Common Pitfalls: Excessive nose radius on a flexible setup can induce chatter; always balance geometry with machine rigidity and feed. Final Answer: All of these

Question 17

Grinding wheel grit size vs. work material A coarse-grained grinding wheel is best suited for which type of materials to avoid wheel loading and improve chip accommodation?

Accepted Answer

Introduction / Context: Wheel selection must match work material characteristics. Grain size affects chip space and cutting aggressiveness. Soft, ductile materials tend to smear and clog wheels, so grit size and structure are crucial to performance and finish. Given Data / Assumptions: Conventional abrasives and bonds (aluminium oxide or silicon carbide). Goal is efficient cutting with minimal loading and burning. Concept / Approach: Coarse grains create larger chip pockets and stronger points, enhancing chip evacuation and reducing loading on ductile materials. For hard-brittle materials, finer grits can control micro-fracture and surface integrity; coarse grit may cause chipping. Step-by-Step Solution: Identify loading tendency on soft, ductile materials.Select coarse grit to increase chip clearance and promote self-sharpening.Conclude: coarse-grained wheels are preferred for soft, ductile materials. Verification / Alternative check: Handbooks advise coarse/open-structure wheels with softer grade for aluminium and mild steels to prevent glazing. Why Other Options Are Wrong: Hard-brittle materials often benefit from finer grit control. “Glass only” is too narrow and misinterprets the role of grit size. Common Pitfalls: Choosing fine, hard wheels on soft metals leads to glazing, heat, and poor finish. Final Answer: Soft and ductile materials

Question 18

How are ceramic cutting inserts mounted? Because of brittleness and thermal-shock sensitivity, ceramic tool tips are usually attached to the tool body by which method?

Accepted Answer

Introduction / Context: Ceramic cutting tools (e.g., alumina-based, SiAlON) offer high hot hardness and chemical stability but are relatively brittle. Their mounting method must avoid thermal damage and allow economical indexing or replacement. Given Data / Assumptions: Indexable insert tooling is used. Operation involves elevated temperatures and intermittent cuts may occur. Desire for easy insert indexing and replacement. Concept / Approach: Mechanical clamping (often with a top clamp and a locating pocket) secures ceramic inserts without subjecting them to the thermal cycles and residual stresses associated with brazing or soldering. This also enables quick indexing of multi-corner inserts. Step-by-Step Solution: Assess material behavior: ceramics are brittle and sensitive to thermal shock.Joining by brazing/soldering introduces thermal cycles and residual stresses → undesirable.Therefore, mechanical clamping is preferred. Verification / Alternative check: Modern toolholder systems (ISO turning holders) are designed around clamped, indexable inserts with chipbreakers and seating geometries. Why Other Options Are Wrong: Brazing or soldering can crack or weaken ceramic tips; welding is inapplicable. Adhesives cannot withstand cutting loads and temperatures. Common Pitfalls: Using excessive clamping force or poor pocket support can fracture ceramics; proper torque and seating cleanliness are critical. Final Answer: Clamping

Question 19

Carbide-tipped tools — typical rake selection For general turning at high speeds, carbide-tipped single-point tools most commonly employ which rake angle strategy to strengthen the edge?

Accepted Answer

Introduction / Context: Rake angle influences cutting forces, edge strength, and heat distribution. Carbide-tipped tools, with high hot hardness but limited toughness compared with HSS, often use negative rake geometry for durability at high speeds and heavy cuts. Given Data / Assumptions: Carbide-tipped or indexable carbide inserts in general steel turning. High cutting speeds and significant cutting temperatures. Machine rigidity sufficient to handle increased forces from negative rake. Concept / Approach: Negative rake geometry thickens the wedge angle, increases edge strength, and places the cutting load more in compression, which carbides tolerate well. While positive rake reduces forces, it thins the wedge and can chip at high loads or interrupted cuts. Step-by-Step Solution: Consider edge strength of carbides vs. HSS → carbide benefits from a stronger wedge.Negative rake increases wedge angle → better edge strength at speed.Thus, negative rake is commonly adopted for carbide-tipped tools in heavy/high-speed work. Verification / Alternative check: ISO insert geometries and chipbreaker designs frequently feature negative basic rake with engineered chip grooves to moderate cutting forces. Why Other Options Are Wrong: Positive rake is used for low-power machines and gummy materials but compromises edge strength. Zero rake is sometimes used, but not the typical choice for robustness across conditions. Exotic alternating rake edges are impractical. Common Pitfalls: Applying negative rake on a flimsy setup can induce chatter; ensure sufficient rigidity and appropriate feeds/speeds. Final Answer: Negative rake angle

Question 20

Determinants of tool life (Taylor’s equation context) Which of the following factors significantly affect tool life in metal cutting operations?

Accepted Answer

Introduction / Context: Tool life governs productivity and cost. Taylor’s tool-life equation relates cutting speed to tool life, but in practice, tool geometry, feed, depth of cut, work material, and cutting environment also influence wear mechanisms like flank wear, crater wear, chipping, and notch wear. Given Data / Assumptions: Conventional turning or milling with properly selected tool material. Stable machine and workholding. Dry or lubricated cutting as applicable. Concept / Approach: Cutting speed strongly affects temperature and diffusion wear (higher speed → shorter life). Tool geometry (rake, clearance, edge prep, nose radius) governs force distribution, heat, and chip flow. Feed rate influences chip load and heat generation, affecting wear and chipping risk. Step-by-Step Solution: Assess cutting speed → exponential impact on tool life (Taylor equation).Assess tool geometry → modifies forces, contact area, and wear patterns.Assess feed rate → higher feed increases load and temperature, usually reducing life. Verification / Alternative check: Empirical tool-life testing and manufacturer application data confirm sensitivity to these variables and recommend parameter windows accordingly. Why Other Options Are Wrong: Picking any single factor ignores the multivariate nature of tool wear. “None” contradicts well-established machining science. Common Pitfalls: Changing only speed to correct wear while ignoring geometry or feed; often a holistic adjustment (including coolant and edge prep) is needed. Final Answer: All of these

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