Question 1

Grinding wheel structure numbering and density  In manufacturing processes, the 'structure' number of a vitrified grinding wheel indicates the relative spacing between abrasive grains. Based on standard wheel nomenclature, is a dense (closely packed…

Accepted Answer

Introduction / Context: Grinding wheel codes include grit size, grade, structure, and bond. Among these, the structure number describes how tightly or loosely the abrasive grains are packed. Correct interpretation of this number influences stock removal rate, wheel wear, and surface finish. Given Data / Assumptions: Conventional vitrified wheels used for general grinding. Structure numbers typically range from about 1 (very dense) to 15 (very open). Other variables (grit size, grade, bond) are kept constant for comparison. Concept / Approach: Structure number ↑ means more spacing and porosity between grains. Dense wheels (low structure number) have more cutting points per unit area and usually produce finer finishes but load more easily. Open wheels (high structure number) admit coolant and chips more readily, useful for softer or gummy materials and heavy cuts. Step-by-Step Solution: Define density: closely packed grains = dense structure.Relate to numbering: lower structure numbers (about 1–5) = dense; higher numbers (about 9–15) = open.Therefore, stating that dense wheels are ”9–15 or higher” is incorrect. Verification / Alternative check: Manufacturing catalogs list structure progression from dense to open as the number increases, confirming the interpretation. Why Other Options Are Wrong: “Only for coarse grits”: structure is independent of grit size. “Depends on grade”: grade is bond hardness, not grain spacing. “Bond type indicates density”: bond affects strength and porosity type, but structure number explicitly denotes spacing. Common Pitfalls: Confusing grade (hard/soft) with structure (dense/open); assuming higher number always means ”more/better.” Final Answer: No, higher structure numbers mean a more open (less dense) wheel

Question 2

Universal milling machine capability  In a universal milling machine, can the table be swiveled in the horizontal plane and also fed at an angle relative to the milling spindle for operations like helical milling?

Accepted Answer

Introduction / Context: A universal milling machine extends the capability of a plain (horizontal) mill by allowing the table to swivel in the horizontal plane. This is essential for cutting helical gears, spirals, and other angular features synchronized with table feed. Given Data / Assumptions: Universal horizontal milling machine with a swivel table. Indexing head and change gears may be available for helical milling. Objective: feed the work at an angle to the cutter axis. Concept / Approach: Swiveling the table changes the feed direction relative to the cutter. When geared (with the dividing head) to the table feed, the work can be advanced axially as it rotates, generating a helix. This capability differentiates the universal mill from a plain mill, whose table is fixed parallel/perpendicular to the spindle. Step-by-Step Solution: Swivel the table to the required helix angle within machine limits.Engage feed at the set angle; optionally gear the dividing head to the feed screw for helices/gears.Perform milling with the desired angular relationship, impossible on a non-swiveling plain mill. Verification / Alternative check: Manufacturer manuals show swivel graduations and helical milling charts, confirming angled feed capability. Why Other Options Are Wrong: Statements restricting feed to straight directions ignore the fundamental design of the universal table. Vertical head attachment is not a prerequisite for horizontal helical milling. Common Pitfalls: Confusing universal with omniversal (which also tilts vertically); overlooking the need to realign after angular work. Final Answer: True – the table can swivel horizontally and be fed at an angle

Question 3

Right-hand single-point turning tool feed direction  On a standard engine lathe, a right-hand tool removes metal most efficiently when fed in which direction along the bed during a straight turning operation?

Accepted Answer

Introduction / Context: Tool “hand” in turning specifies the chip flow direction and which side of the tool contains the major cutting edge. Getting the feed direction right is fundamental to safe, chatter-free cutting and good surface finish. Given Data / Assumptions: Single-point right-hand tool with the main cutting edge on the right when viewed from above. Conventional right-hand spindle rotation driving the workpiece. Concept / Approach: A right-hand tool is designed to cut when it advances toward the headstock, i.e., from the right side of the work toward the left. This keeps the cutting edge engaged correctly and provides favorable chip flow away from the finished surface. Step-by-Step Solution: Mount the right-hand tool with proper rake and clearance.Feed the carriage from the tailstock side toward the headstock (right to left).Observe stable chip formation and reduced tendency to rub. Verification / Alternative check: Standard lathe handbooks depict right-hand tools cutting toward the headstock and left-hand tools cutting away from it. Why Other Options Are Wrong: Left-to-right feed suits a left-hand tool in straight turning. Compound feed and facing are special cases not required for ordinary straight turning. Common Pitfalls: Mounting the tool at incorrect height; confusing “right-hand tool” with “tool mounted on the right of the work.” Final Answer: From right to left end of the bed (towards headstock)

Question 4

Identifying saw milling (slotting) operation on a milling machine  Which statement best describes the saw milling operation among common milling processes?

Accepted Answer

Introduction / Context: Milling operations are named after the cutter form and intended feature. “Saw milling” uses a thin, disc-type cutter (metal slitting saw) to create narrow cuts with minimal kerf, essential for keyways, slots, and cut-offs. Given Data / Assumptions: Horizontal or vertical milling machine setup. Use of a metal slitting saw or slotting saw. Concept / Approach: Saw milling focuses on producing narrow slots or slits. The cutter resembles a circular saw with closely spaced teeth, optimized for straight, narrow grooves with clean edges and controlled width corresponding to the saw thickness. Step-by-Step Solution: Mount a slitting saw on an arbor with proper spacers and stiff support.Set depth and feed to achieve the desired slot without deflection.Feed the work to produce the narrow groove or cut-off. Verification / Alternative check: Textbooks classify saw milling under slotting/slitting operations, distinct from profiling and gang milling. Why Other Options Are Wrong: Grooves around a cylindrical periphery refer to gear or spline milling. Template reproduction is profiling or tracer milling. Gang milling uses multiple cutters to machine several surfaces at once. Common Pitfalls: Using an overly thin saw for deep slots, leading to chatter; insufficient arbor support causing wander. Final Answer: Producing narrow slots or grooves on a flat or shaped workpiece using a metal slitting saw

Question 5

Which milling machine allows vertical-plane table tilt via a knee swivel?  Considering common machine tool types, identify the machine whose table can be tilted in the vertical plane using a swivel mechanism at the knee (in addition to a horizontal …

Accepted Answer

Introduction / Context: Machine tool versatility is defined by available swivels and tilts. A universal mill has a horizontal swivel table for helical work, while the omniversal extends adjustability by adding a vertical-plane tilt at the knee. Given Data / Assumptions: Distinguishing between “universal” and “omniversal.” Looking specifically for vertical-plane tilt at the knee, not just horizontal swivel. Concept / Approach: A universal milling machine’s hallmark is a table that swivels about a vertical axis (horizontal-plane swivel). The omniversal milling machine adds an additional swivel (or hinge) at the knee to tilt the table in a vertical plane, enabling compound angle machining and complex helixes not possible on a standard universal mill. Step-by-Step Solution: Identify the required feature: vertical-plane tilt at the knee.Match with machine types: only the omniversal provides both horizontal swivel and vertical tilt via knee arrangement.Therefore, select omniversal milling machine. Verification / Alternative check: Manufacturer catalogs show omniversal machines with dual swivels, often depicted with tilt scales at the knee. Why Other Options Are Wrong: Universal: horizontal swivel only. Plain: neither horizontal nor vertical swivel at the table. Hand/turret mill: may tilt the head, not the table via a knee swivel as specified. Common Pitfalls: Assuming “universal” means fully adjustable in all planes; confusing head tilt with table/knee tilt. Final Answer: Omniversal milling machine

Question 6

Tool life in continuous vs. intermittent cutting  Considering thermal and mechanical loading at the cutting edge, how does tool life in continuous cutting compare with intermittent cutting under similar conditions?

Accepted Answer

Introduction / Context: Tool life is strongly affected by thermal cycling, impact loads, and chip load continuity. Processes like turning and boring are largely continuous; milling interrupted; keyways or interrupted forgings introduce impact on each revolution. Given Data / Assumptions: Same tool/work materials and cutting parameters as far as practical. Intermittent cutting introduces repeated entry/exit of the edge. Concept / Approach: Intermittent cutting causes periodic mechanical impact and thermal shock as the edge contacts and leaves the work, leading to micro-chipping and edge fatigue. Continuous cutting maintains more stable temperature and force, lengthening tool life for HSS, carbide, and ceramics (the latter are especially sensitive to thermal shock). Step-by-Step Solution: Compare loading: continuous = steady; intermittent = cyclic impact.Cyclic stresses accelerate crack initiation at the cutting edge.Result: tool life is generally longer in continuous cutting. Verification / Alternative check: Machining handbooks advise reduced speed or special grades/coatings for interrupted cuts to regain tool life, confirming the disadvantage of intermittent cutting. Why Other Options Are Wrong: “Better due to cooling”: thermal shock outweighs any cooling benefit. “Identical if speed reduced”: reducing speed helps but does not make them equal. “Random/always preferred for finishing”: finishing usually seeks continuity for surface integrity. Common Pitfalls: Using brittle ceramic inserts on heavy interrupted cuts without proper techniques. Final Answer: Continuous cutting gives much better tool life than intermittent cutting

Question 7

Taps and chamfer lengths  Which statement correctly describes a taper tap used to start internal threads in a blind or through hole?

Accepted Answer

Introduction / Context: Hand tapping generally uses a set of three: taper (starter), plug (second), and bottoming taps. The chamfer length determines how gradually the tap engages, affecting alignment, torque, and chip load. Given Data / Assumptions: Taper tap is the first tap in the sequence. Used to initiate thread form accurately and reduce starting torque. Concept / Approach: The taper tap has the longest chamfer, typically 8–10 threads, which gradually forms the thread. The plug tap follows with about 3–5 chamfered threads, and the bottoming tap has 1–2, enabling threads to the bottom of a blind hole. Step-by-Step Solution: Identify function: start the thread straight with low torque.Require long lead-in: hence 8–10 thread chamfer on taper tap.Confirm other tap types: plug (3–5), bottoming (1–2). Verification / Alternative check: Workshop charts and tap manufacturers specify typical chamfer ranges consistent with the above. Why Other Options Are Wrong: 3–4 threads describes a plug tap more closely. Full threads/no chamfer would make starting nearly impossible. Bottoming and taper taps are not identical; they serve different stages. Common Pitfalls: Trying to start a hole with a bottoming tap; misalignment causing cross-threading. Final Answer: Its end is tapered over about eight to ten threads

Question 8

Material removal in lapping operations  In precision finishing (lapping), what is the typical total metal removed from a surface during the process?

Accepted Answer

Introduction / Context: Lapping is an ultra-precision finishing method used to achieve very fine surface finishes and tight flatness tolerances using loose abrasives in a fluid vehicle between a lap and the workpiece. Given Data / Assumptions: Final finishing after grinding or honing. Loose abrasive grains (e.g., Al2O3, SiC) on a soft lap plate. Concept / Approach: Lapping removes extremely small amounts of material, correcting minor shape errors and surface peaks left by previous processes. Excessive stock removal would defeat its purpose and consume undue time, as removal rates are very low compared to grinding or milling. Step-by-Step Solution: Estimate objective: improve flatness/finish, not major dimension change.Typical stock removal per surface is a few micrometres to a few tens of micrometres.Thus the representative range is about 0.005–0.01 mm (5–10 micrometres). Verification / Alternative check: Process data from lap equipment vendors indicate removal rates on the order of micrometres per minute for many metals. Why Other Options Are Wrong: 0.01–0.1 mm and above are typical for honing/light grinding, not fine lapping. 0.5–1.0 mm or more is rough machining territory. Common Pitfalls: Expecting lapping to correct large geometry errors; using overly aggressive abrasives that scratch instead of polish. Final Answer: 0.005 to 0.01 mm

Question 9

Cutting temperature for maximum material removal with carbide on mild steel  When machining a mild steel workpiece using a carbide tool under typical shop conditions, around which cutting temperature is maximum material removal rate commonly associa…

Accepted Answer

Introduction / Context: Cutting temperature at the tool–chip interface affects shear strength of the work material, tool wear mechanisms, and achievable speed. Carbide tools retain hardness at higher temperatures than HSS, enabling higher speeds and material removal rates (MRR) on steels. Given Data / Assumptions: Mild steel work material. Carbide tool, conventional flood coolant or dry with reasonable parameters. Seeking a representative temperature where MRR is high yet tool wear is manageable. Concept / Approach: As cutting temperature increases, the material softens in the shear zone, lowering cutting forces and allowing higher speeds/feeds. However, too high a temperature accelerates crater and flank wear, reducing tool life and making sustained high MRR impractical. Practical shop experience places efficient production for mild steel with carbide at a few hundred degrees Celsius. Step-by-Step Solution: Consider the trade-off: low temperature (50–175°C) → high strength and high forces → limited MRR.Moderate-high temperature (~275°C) → reduced shear strength, stable chip formation → high sustainable MRR for carbide.Very high temperature (>500°C) → excessive wear and thermal damage risks. Verification / Alternative check: Speed–tool-life charts (Taylor’s equation) for carbide on low-carbon steel support higher allowable speeds and temperatures than HSS, with practical thermal levels of a few hundred °C during efficient cutting. Why Other Options Are Wrong: 50–175°C: typically too low for efficient carbide cutting on steel. “Above 500°C always required” overstates and risks rapid wear. Common Pitfalls: Confusing tool capability to withstand temperature with the optimal operating window for sustained production and tool life. Final Answer: 275°C

Question 10

Types of broaching motions  Which broaching operation is characterized by either the work or the tool moving across the other to generate external planar or contoured surfaces (rather than purely internal holes or keyways)?

Accepted Answer

Introduction / Context: Broaching uses a toothed tool with progressively increasing tooth height to remove material in a single pass. Different broaching modes address internal forms, external flats, and production flow requirements. Given Data / Assumptions: Comparison among pull/push, surface, and continuous broaching. Looking specifically for “moving across the other” to generate external surfaces. Concept / Approach: Internal broaching (pull or push) draws or pushes the broach through a preformed hole to create splines, keyways, or polygonal shapes. Surface broaching moves the broach across an external surface (or moves the work under a stationary broach) to machine flats, slots, or contours. Continuous broaching refers to a production method where multiple parts travel past multiple broaches on a conveyor-like machine. Step-by-Step Solution: Identify the motion: cross-wise relative motion between tool and work.Match to process: this is surface broaching.Therefore, select surface broaching as the correct operation. Verification / Alternative check: Process descriptions and schematics show surface broaches mounted on slides while the work reciprocates or feeds continuously beneath them. Why Other Options Are Wrong: Pull/push broaching: internal, along the hole axis. Continuous broaching: a production arrangement, not a motion definition; may be internal or surface depending on tooling. Rotary broaching is a separate process done in lathes to form polygons in holes. Common Pitfalls: Equating continuous broaching with surface broaching; overlooking fixturing needed to support long broaches in pull operations. Final Answer: Surface broaching

Question 11

Grinding wheel selection for high stock removal: For fast removal of material during grinding operations (heavy roughing), which grain size specification should be preferred?

Accepted Answer

Introduction / Context: Choosing the proper grinding wheel is critical for productivity and surface integrity. One of the most important parameters is grit size (grain size). When the objective is fast stock removal — for example, rough grinding to quickly reduce dimensions — the grit size and wheel structure must allow large chips to form and escape without loading or glazing. Given Data / Assumptions: Abrasive machining of steels or common shop alloys. Goal is high material removal rate (MRR), not surface finish. Conventional bonded abrasives (aluminium oxide or silicon carbide). Concept / Approach: Coarse grits have larger cutting points that penetrate deeper, forming thicker chips and enabling higher MRR. They also create larger chip spaces, reducing wheel loading. Fine grits, by contrast, produce many small cutting edges, ideal for fine finishes but limited in chip thickness and MRR. Medium grits compromise between the two. Wheel structure (open vs dense) further modulates chip clearance, but the primary lever for stock removal is coarse grit size. Step-by-Step Solution: Define objective → maximize stock removal (roughing stage).Relate objective to grit size → larger grit cuts deeper per grain.Select wheel → coarse grained wheel to carry thick chips and resist loading. Verification / Alternative check: Shop practice recommends coarse, open-structure wheels with soft-to-medium grade for aggressive roughing; trial cuts will show lower power spikes and less glazing compared to fine grit wheels for the same feed and depth of cut. Why Other Options Are Wrong: Fine grained: optimized for finish, not for heavy MRR. Medium grained: balanced choice, still not optimal for maximum MRR. Micro-grained superfinish: designed for very fine finishes at minimal stock removal. Closed structure with small grit: tends to load up under heavy chip volume. Common Pitfalls: Confusing wheel grade (bond hardness) with grit size; both matter, but grit size primarily controls chip thickness for a given condition. Also, forgetting to ensure adequate coolant and wheel dressing for sustained roughing performance. Final Answer: coarse grained

Question 12

Oblique cutting system: Identify the correct description(s) of geometry and chip flow for oblique (non-orthogonal) cutting.

Accepted Answer

Introduction / Context: Metal cutting is broadly categorized into orthogonal and oblique cutting. Oblique cutting is the more general and more common case in real machining, where the cutting edge is not perpendicular to the cutting velocity. Recognizing its geometric features helps predict chip flow, forces, and surface finish characteristics. Given Data / Assumptions: Steady-state machining, no built-up edge considered. Tool has a finite inclination (obliquity) angle i. Cutting takes place with a single-point tool (but multiple edge segments may engage in oblique geometry). Concept / Approach: In oblique cutting, the major cutting edge is inclined, producing a chip flow direction that is neither purely upward nor purely normal to the cutting edge. The chip flows sideways across the rake face, giving a three-dimensional chip flow vector. This often results in more favorable chip evacuation and can influence surface finish and tool life. Step-by-Step Solution: Note geometry → cutting edge is inclined, not perpendicular to tool velocity.Infer chip flow → oblique to the normal on the cutting edge, typically at a finite chip flow angle.Acknowledge edge participation → depending on nose radius and inclination, more than one edge portion may contribute concurrently. Verification / Alternative check: Draw the 3D velocity diagram: the chip velocity has components both normal to and along the cutting edge, confirming oblique chip flow and the described angles. Why Other Options Are Wrong: Here, options (a), (b), and (c) collectively describe oblique cutting; dismissing any one would leave the description incomplete. Therefore, “all of the above” is the most accurate choice. Common Pitfalls: Assuming orthogonal cutting applies to most turning operations; in practice, nose radius and lead/inclination angles make the process oblique. Also, confusing rake angles (back/side) with the inclination that defines oblique geometry. Final Answer: all of the above

Question 13

Lathe kinematics: When a single-point tool moves parallel to the lathe axis during turning, this motion is termed as which feed?

Accepted Answer

Introduction / Context: On a lathe, the feed direction determines the surface generated. Understanding the nomenclature of feeds helps in selecting the proper motion for operations like straight turning, facing, and taper turning. The question asks you to identify the term used when the tool advances parallel to the spindle (work) axis. Given Data / Assumptions: Conventional engine lathe with carriage and cross-slide. Single-point turning tool in a standard turning operation. No taper attachment engaged. Concept / Approach: Lathe feeds are classified primarily as longitudinal (parallel to spindle axis) and cross (radially toward/away from the axis). Longitudinal feed machines a cylindrical surface; cross feed produces facing cuts or changes in diameter. Angular or compound feeds combine motions to generate tapers or profiles. Step-by-Step Solution: Identify tool direction → parallel to the work axis.Match with lathe terminology → longitudinal feed.Conclude that straight turning uses longitudinal feed to generate a cylinder. Verification / Alternative check: On the carriage, engaging the feed rod with the half-nuts and moving the saddle along the bed provides longitudinal feed; micrometer dials confirm axial travel, not radial. Why Other Options Are Wrong: Cross feed: radial motion, used for facing and diameter adjustments. Angular/compound feed: combination of slides to produce tapers; not strictly parallel to the axis. Taper feed: informal term; actual mechanism is compound or taper attachment. Common Pitfalls: Confusing carriage (longitudinal) movement with cross-slide movement; always visualize the axis of the work to determine the feed designation. Final Answer: longitudinal feed

Question 14

Hot machining methods: In hot machining (thermally assisted cutting), the workpiece is preheated by which of the following practical methods before cutting?

Accepted Answer

Introduction / Context: Hot machining, also called thermally assisted machining, intentionally heats the workpiece prior to or during cutting to lower flow stress, reduce cutting forces, and improve machinability of hard-to-cut alloys, ceramics, or high-strength steels. Several heating methods are used depending on material, geometry, and shop capability. Given Data / Assumptions: Goal: reduce cutting resistance and tool wear by raising the work material temperature. Applicable to difficult materials (e.g., nickel superalloys, hardened steels) and certain ceramics. Heating methods must be controllable and compatible with the work environment. Concept / Approach: Heating reduces yield strength and hardness of many alloys, allowing larger depth of cut or higher feeds at the same tool load. Common heating methods include simple resistance or furnace preheat (for bars/forgings), localized flame heating, and rapid, controllable induction heating. Choice depends on required temperature, depth of heating, and production rate. Step-by-Step Solution: Identify objective → soften near-surface layer before cutting.Match heating method to scenario → resistance/furnace, flame, or induction all valid.Conclude → any of the listed methods can be used in hot machining. Verification / Alternative check: Industrial case studies report force reductions and tool-life gains when induction or flame preheating is applied ahead of the tool in turning or milling of heat-resistant alloys. Why Other Options Are Wrong: Each individual method by itself is correct; restricting to only one would be incomplete. Therefore the inclusive choice is correct. Common Pitfalls: Overheating causing metallurgical damage or loss of dimensional control; insufficient shielding can oxidize surfaces. Temperature monitoring (pyrometers, paints) and proper parameter control are essential. Final Answer: any one of these

Question 15

Tool life exponent for ceramics: In the Taylor tool life relation V * T^n = C, which range best represents the typical exponent n for ceramic cutting tools under usual machining conditions?

Accepted Answer

Introduction / Context: The Taylor tool life equation V * T^n = C relates cutting speed V and tool life T via the tool-material-dependent exponent n. Knowing typical n values guides speed optimization and tool change planning. Ceramics have distinct wear behavior compared to high-speed steel (HSS) and carbides, reflected in a larger exponent. Given Data / Assumptions: Dry or minimally lubricated cutting appropriate for ceramics. Continuous or lightly interrupted cuts on cast iron/hardened steels. Normal ranges accepted from machining handbooks (order-of-magnitude accuracy). Concept / Approach: Typical n ranges: HSS around 0.08–0.20, carbides around 0.20–0.25 (sometimes up to ~0.30), and ceramics around 0.40–0.60 depending on grade and application. Higher n implies tool life is more sensitive to changes in cutting speed; small speed increases can sharply reduce T for ceramics. Step-by-Step Solution: Identify target material class → ceramic cutting tools.Recall handbook ranges → n approximately 0.4–0.55 (commonly cited band).Select the option that matches this range. Verification / Alternative check: Vendor application data for alumina or SiAlON tools typically show n near 0.45–0.55 for hardened steels and cast irons in continuous turning, corroborating the selected range. Why Other Options Are Wrong: 0.10–0.20 and 0.20–0.25: characteristic of HSS and carbides, respectively. 0.25–0.40: transitional values; usually low for ceramics. 0.60–0.80: higher than common practice and not typical of general ceramic machining conditions. Common Pitfalls: Applying a single n value universally; grade, work material, and cooling strongly influence n. Interrupted cuts or thermal shock conditions may deviate from handbook values. Final Answer: 0.40 to 0.55

Question 16

Grinding wheel grit size selection: The required abrasive grain size for a grinding wheel primarily depends on which factors?

Accepted Answer

Introduction / Context: Grit size influences chip thickness, cutting force, and final surface finish in grinding. Selecting the proper grain size ensures the right balance between productivity and quality. The decision involves more than a single parameter; it is a multi-factor choice reflecting stock removal needs, work material properties, and finish specifications. Given Data / Assumptions: Conventional bonded abrasive wheels (aluminium oxide or silicon carbide). Shop objectives may vary from roughing to fine finishing. Wheel structure and grade are held constant for discussion; focus is on grit size. Concept / Approach: Coarse grits remove stock quickly and tolerate large chip thickness, preferred for heavy allowances and tough materials when finish is secondary. Fine grits create many small cutting points for superior finish and dimensional control, especially on hard or brittle materials. Work material hardness affects grit choice: harder materials often require finer grits to avoid micro-fracturing of the surface and to maintain stable cutting action. Step-by-Step Solution: Define stock removal → more stock favors coarser grit.Assess material hardness → harder materials often benefit from finer grit for control.Set finish target → tighter finish tolerances favor finer grit. Verification / Alternative check: Reference selection charts from wheel manufacturers correlate grit size with material hardness and finish grade; they consistently consider all three factors together. Why Other Options Are Wrong: Each single factor is relevant; therefore picking only one would be incomplete. The comprehensive and correct choice includes all listed factors. Common Pitfalls: Ignoring the interaction with wheel grade and structure; grit size should be chosen together with bond hardness and porosity to avoid wheel loading or excessive wear. Final Answer: all of these

Question 17

Single-point tool terminology: “The part of the tool on which the cutting edge is formed is called the nose.” — Evaluate the correctness of this statement.

Accepted Answer

Introduction / Context: Accurate nomenclature is essential for tool grinding and setup. Mislabeling tool regions leads to confusion in specifying rake, relief, and nose radius. The statement conflates general cutting edges with the localized tip geometry called the “nose.” Given Data / Assumptions: Standard single-point turning tool with major and minor cutting edges. A defined nose (tip) typically with a nose radius joining the edges. Tool faces: rake face and flank faces where edges are formed. Concept / Approach: The cutting edges are formed by the intersection of the rake face with the flank faces (major and minor). The “nose” is the region at the junction of these edges, often blended with a radius to improve finish and distribute stresses. Therefore, the nose is not the whole surface “on which” the cutting edge is formed; rather, it is a specific small area at the tool tip that participates in finishing and corner strength. Step-by-Step Solution: Identify edge formation → intersection of rake and flank faces.Define nose → localized tip where major and minor edges meet, usually radiused.Compare with statement → it incorrectly equates nose with the broader edge-forming surfaces. Verification / Alternative check: Tool signature charts (ASA/ISO) list separate parameters for side/ end relief and back/ side rake, plus nose radius — confirming noses are distinct features, not the entire edge-forming faces. Why Other Options Are Wrong: Conditionally “correct” answers (for specific tool types or orthogonal cutting) remain incorrect; the definition of nose is consistent across tool materials and cutting modes. Common Pitfalls: Calling any rounded edge “the nose”; in fact, the nose is the corner region only, and excessive radius can cause chatter or size errors if not matched to feed and rigidity. Final Answer: Incorrect

Question 18

Grinding wheel structure: A dense (closely spaced grain) wheel is most appropriately used for which application?

Accepted Answer

Introduction / Context: Besides grit size and bond grade, wheel structure (spacing between abrasive grains) affects chip accommodation and heat generation. Dense structures have more grains per unit volume with smaller chip spaces; open structures have fewer grains and larger pores. Correct structure selection prevents loading and controls finish. Given Data / Assumptions: Conventional vitrified or resinoid bonded wheels. Need to distinguish roughing vs finishing performance. Materials may range from soft ductile to hard/brittle substrates. Concept / Approach: Dense wheels place many cutting points in contact, distributing load and generating a fine finish at shallow chip thickness. They suit finishing operations and tight tolerances. For roughing soft or gummy materials, an open structure is preferred to provide chip clearance and reduce wheel loading. While dense wheels can be used on hard/brittle materials when finishing, stating “all of these” is overly broad; the most defensible single best answer is “finishing cuts requiring fine surface.” Step-by-Step Solution: Clarify objective → finishing vs roughing.Relate structure to chip space → dense structure means small chip pockets, favoring fine finish.Select application → finishing cuts are best served by dense wheels. Verification / Alternative check: Manufacturer selection guides associate dense structures (and finer grits) with finishing passes and dimensional grinding; open structures are recommended for heavy stock removal and soft, ductile materials. Why Other Options Are Wrong: Hard materials: often finished with dense wheels, but for roughing hard materials, chip clearance may still be needed. Brittle materials: may also finish well with dense wheels, yet as a general rule the single most precise answer is the finishing application. All of these: too inclusive and not universally valid. Roughing soft, gummy materials: requires open structure to avoid loading. Common Pitfalls: Assuming “denser is always better.” Dense wheels can overheat work surfaces and load rapidly when asked to remove heavy stock on ductile materials. Final Answer: finishing cuts requiring fine surface

Question 19

Cutting tool classification by operation: What type of cutting tool is typically used on a milling machine and on a broaching machine?

Accepted Answer

Introduction / Context: Different machine tools employ cutting tools with distinct edge configurations. Recognizing whether an operation uses single- or multi-point tools helps anticipate chip formation, cutting forces, and achievable surface finish. Milling cutters and broaches have many teeth, making them classic examples of multi-point tools. Given Data / Assumptions: Milling: slab, end, face, or form cutters with multiple flutes/teeth. Broaching: a broach with a progressive row of teeth increasing in height (rise per tooth). Continuous metal cutting (not scraping or grinding). Concept / Approach: A single-point tool has one major cutting edge (e.g., a turning tool on a lathe). Multi-point tools possess multiple edges engaged either simultaneously or sequentially (milling teeth, broach teeth). Multiple teeth share the load and can produce high MRR and better surface finishes under the right conditions. Step-by-Step Solution: Identify tool type in milling → cutter with many flutes/teeth.Identify tool type in broaching → long tool with many progressively taller teeth.Conclude → both are multi-point cutting tools. Verification / Alternative check: Standard textbooks classify milling cutters and broaches as multi-tooth, differentiating them from the single-point lathe tool and the two-point boring bar with twin edges (special cases). Why Other Options Are Wrong: Single/two/three-point: do not describe milling and broaching accurately. Scraper: not a chip-forming cutting tool for these machines. Common Pitfalls: Counting only the number of teeth engaged at any instant; even if just one or a few teeth cut at a time, the tool is still classified as multi-point by design. Final Answer: multi-point cutting tool

Question 20

Drill geometry for soft alloys: For drilling aluminium and other soft, ductile materials, the recommended drill helix angle is typically greater than 30°. Evaluate the statement.

Accepted Answer

Introduction / Context: Drill helix (rake) angle influences chip evacuation and cutting action. Soft, ductile materials like aluminium produce continuous, long chips that require efficient lifting and removal from the hole to avoid packing and surface damage. Tool geometry is adjusted accordingly. Given Data / Assumptions: General-purpose twist drills for aluminium and similar soft metals. Adequate lubrication or mist is available to reduce built-up edge. HSS or carbide drills used under normal shop conditions. Concept / Approach: Higher helix angles (often 35°–45°) provide a more aggressive rake and larger flute volume, enhancing chip lifting and evacuation. This reduces the tendency of chips to jam, lowers cutting forces, and improves hole finish. In contrast, low helix angles are favored for hard or abrasive materials to strengthen the cutting edge and moderate chip flow. Step-by-Step Solution: Identify work material → aluminium (soft, ductile, continuous chips).Match geometry → higher helix angle improves chip evacuation.Conclude → the statement that helix angle is more than 30° is correct. Verification / Alternative check: Tool catalogs list “aluminium geometry” drills with 35°–45° helix, polished flutes, and sharper point/rake to resist built-up edge and improve chip flow. Why Other Options Are Wrong: Disagree/low helix recommendations contradict widely accepted practice for ductile chip forms. Limiting correctness to specific alloys or carbide tools is unnecessary; the principle holds for both HSS and carbide across most aluminium grades. Common Pitfalls: Using standard 30° helix without polished flutes may still work but can increase chip packing in deep holes. Peck drilling and proper coolant further improve results with high helix designs. Final Answer: Agree

Production Engineering Questions