Question 1

In metal cutting, the velocity component of chip flow that moves along the rake (tool) face is referred to as which specific velocity?

Accepted Answer

Introduction / Context: Understanding velocity components in machining helps interpret forces, heat generation, and tool wear. Three commonly referenced velocities are the cutting (work) velocity, the shear (on the primary shear plane), and the chip velocity that slides along the rake face. This question asks you to correctly name the velocity along the tool face. Given Data / Assumptions: Single-point orthogonal or oblique cutting on a lathe-like setup. Standard nomenclature: cutting velocity V, shear velocity Vs, and chip (or chip flow) velocity Vc (along rake face). Steady-state cutting with continuous chip for clarity. Concept / Approach: In the velocity triangle of orthogonal cutting, V is the work velocity, Vs lies on the shear plane, and Vc follows the rake face. The chip velocity is directly tied to friction, heat, and wear at the tool–chip interface, because it is the sliding speed between chip and rake face. Step-by-Step Solution: Identify the direction ‘‘along the tool face’’ → this is the rake face.The sliding motion of chip on the rake face defines chip flow speed.Therefore, the correct term is chip velocity. Verification / Alternative check: Construct the classic Merchant velocity triangle; the side parallel to the rake face is the chip velocity vector, confirming the definition. Why Other Options Are Wrong: Shear velocity: acts along the shear plane, not the rake face. Cutting velocity: the work surface speed past the tool; not along the rake face. Mean velocity/tool approach velocity: nonstandard or ambiguous terms here. Common Pitfalls: Confusing cutting velocity with chip velocity because both are large magnitudes; remember their directions differ in the velocity triangle. Final Answer: chip velocity

Question 2

In production engineering, what is the principal purpose of using jigs and fixtures during machining and assembly operations?

Accepted Answer

Introduction / Context: Jigs and fixtures are essential workholding and guidance devices in manufacturing. They position, clamp, and locate parts while guiding tools (jigs) or simply holding the work (fixtures) to reduce variability and increase throughput. The question probes their broad benefits on quality and cost. Given Data / Assumptions: Repetitive or batch production environment. Standardized components with specified tolerances. Skilled or semi-skilled operators using dedicated setups. Concept / Approach: By ensuring consistent location and orientation, jigs and fixtures reduce setup errors and improve repeatability. This raises accuracy, enables interchangeability (parts fit without selective assembly), and reduces inspection time and rework, lowering quality control expenditure overall. Step-by-Step Solution: Relate positional repeatability to dimensional accuracy → fewer deviations.Interchangeability follows from reduced dimensional scatter across batches.Lower inspection and scrap costs result from fewer defects and faster checks. Verification / Alternative check: Compare process capability indices (Cp/Cpk) with and without dedicated fixtures; capability improves, supporting reduced QC costs and higher first-pass yield. Why Other Options Are Wrong: Each single benefit is valid, but the full purpose is comprehensive, so “all of these” is best. “None of these” contradicts established manufacturing practice. Common Pitfalls: Assuming jigs/fixtures only improve speed; in reality, accuracy and consistency gains are primary and directly influence cost and quality. Final Answer: all of these

Question 3

Identify the trade name of the cobalt–chromium–tungsten non-ferrous cast alloy widely used for wear-resistant cutting edges and hot-hard applications.

Accepted Answer

Introduction / Context: Tool and wear-resistant materials are chosen for hot hardness, chemical stability, and toughness. Cobalt–chromium–tungsten cast alloys became famous under a specific trade name for high-temperature and abrasion resistance in valves, dies, and some cutting applications. Given Data / Assumptions: Non-ferrous, cast alloy system containing Co–Cr–W. Application focus: wear resistance and hot hardness. Recognition of common tooling trade names. Concept / Approach: Stellite is a family of cobalt-base alloys with chromium and tungsten (often carbon as well), known for excellent hardness at elevated temperature and corrosion resistance. It is not the same as cemented carbides (WC-Co) nor ceramics/cermets, and “diamond” is a superabrasive, not a metallic cast alloy. Step-by-Step Solution: Match composition Co–Cr–W → associated with Stellite family.Exclude ceramics/diamond (nonmetallic or superabrasive) and cemented carbide (WC particles in Co binder).Therefore, the trade name is Stellite. Verification / Alternative check: Materials handbooks list Stellite grades (e.g., Stellite 6) with characteristic properties and cast/weld overlay applications. Why Other Options Are Wrong: Ceramic/diamond: not metallic cast alloys of Co–Cr–W. Cemented carbide: composite of tungsten carbide grains in cobalt, not a Co–Cr–W cast alloy. Cermet: ceramic–metal composite, different class. Common Pitfalls: Confusing Stellite with tungsten carbide because both involve cobalt; their chemistry, microstructure, and processing differ significantly. Final Answer: stellite

Question 4

Machine specifications: The conventional size designation of a shaper machine is based primarily on which parameter?

Accepted Answer

Introduction / Context: Machine tools are often classified by a characteristic capacity dimension that tells users what size of work can be accommodated. For shaper machines, the reciprocating ram stroke is the defining capacity measure used in catalogs and shop specifications. Given Data / Assumptions: Conventional, ram-type shaper with adjustable stroke. Standard industry naming practice. Stroke relates directly to maximum linear travel over the work. Concept / Approach: The shaper produces flat surfaces via a linear reciprocating cutting motion. The maximum useful length of cut is bounded by the ram stroke; thus stroke length most directly reflects the largest work length that can be machined in a single pass, making it the logical size designation. Step-by-Step Solution: Identify key capacity constraint → maximum ram stroke.Correlate stroke with maximum job length and setup envelope.Conclude that shaper “size” is given by stroke length. Verification / Alternative check: Check manufacturer nameplates: models are listed as, for example, “18 in shaper,” indicating 18-inch maximum stroke. Why Other Options Are Wrong: Motor power and machine mass vary with design and accessories, not the principal capacity metric. “Rate size” is not a standard term. Table width is important but not the conventional shaper size designation. Common Pitfalls: Assuming power rating defines size; while it influences capability, capacity naming follows stroke length for shapers. Final Answer: stroke length

Question 5

For finishing a blind hole by hand or machine reaming, which reamer flute style is preferred to control chip evacuation and protect the finished surface?

Accepted Answer

Introduction / Context: Reamer flute geometry governs chip flow. In blind holes, chips must be directed back toward the shank to avoid packing at the bottom, which would score the surface or prevent reaching size. The question focuses on choosing the correct spiral direction. Given Data / Assumptions: Blind hole (bottom present); finishing to size by reaming. Requirement: clean evacuation away from the bottom. Standard right- or left-hand spiral flutes available. Concept / Approach: Right hand spiral flutes tend to lift chips back toward the shank when the tool rotates in the conventional right-hand direction, making them suitable for blind holes. Left hand spiral reamers drive chips forward and are more suitable for through holes. Straight flutes give neutral chip flow and may pack chips in blind holes. Step-by-Step Solution: Identify hole type → blind hole.Select flute that evacuates chips upward → right hand spiral.Avoid pushing chips into the bottom → do not use left hand spiral in this case. Verification / Alternative check: Tool vendor catalogs explicitly recommend right hand spiral for blind holes and left hand spiral for through holes to manage chip flow safely. Why Other Options Are Wrong: Straight flute: poor chip lifting; risk of scoring and jam. Left hand spiral: pushes chips downward; bad for blind holes. “Any one of these” is unsafe; choice is application-specific. Common Pitfalls: Confusing drill flute direction rules with reamer recommendations; always verify chip direction relative to rotation and flute hand. Final Answer: right hand spiral fluted reamer

Question 6

Cutting fluids and tool life: State whether the following is true or false — “Cutting fluid has no effect on the tool life.”

Accepted Answer

Introduction / Context: Cutting fluids influence temperature, friction, chip evacuation, and built-up edge formation. These directly impact wear mechanisms such as abrasion, adhesion, diffusion, and oxidation, thereby affecting tool life significantly in many materials and operations. Given Data / Assumptions: Conventional turning, drilling, or milling of steels and nonferrous alloys. Appropriate fluid selection (emulsion, straight oil, or synthetics). Proper delivery to the cutting zone. Concept / Approach: Cooling reduces average and peak temperatures; lubrication lowers tool–chip and tool–work friction; flushing clears chips, reducing abrasion and BUE. All three extend tool life, often substantially, especially with HSS and carbide tools at moderate to high speeds. Step-by-Step Solution: Identify main wear drivers → temperature and friction.Apply cutting fluid → reduces temperature and friction.Result → slower wear progression → longer tool life. Verification / Alternative check: Comparative tool life tests (VT^n = C) show higher C when coolant is used appropriately versus dry cutting in many cases. Why Other Options Are Wrong: “True” contradicts abundant industrial evidence. “Only at very low speeds/for ceramics” are conditional statements; while some ceramics run dry, the general claim remains false. Common Pitfalls: Assuming fluids always help; in high-speed machining of certain materials or with ceramics/CBN, dry cutting may be preferred to avoid thermal shock—context matters. Final Answer: False

Question 7

Single-point tool nomenclature: The angle between the flank surface immediately below the tool point and a line drawn from the point perpendicular to the base (reference plane) is termed the

Accepted Answer

Introduction / Context: Relief (clearance) angles prevent rubbing between the tool flank and the newly generated work surface. Proper identification of end versus side relief is crucial for tool grinding and for avoiding excessive wear or chatter. Given Data / Assumptions: Standard ASA/ISO tool signature conventions. Plan and side views used to define rake and relief angles. Reference plane is the base or machine reference for angle measurement. Concept / Approach: End relief angle is measured on the end flank beneath the tool nose relative to a line perpendicular to the base; side relief is measured on the side flank beneath the main cutting edge. Rake angles (back and side) refer to the rake face and influence chip flow, not clearance behind the cutting edge. Step-by-Step Solution: Locate the flank immediately below the point (end flank).Construct a perpendicular to the base from the point.Measure the included angle → this is the end relief angle. Verification / Alternative check: Compare with side relief definition; it references the side flank and the main cutting edge direction, distinguishing it from the end relief at the nose. Why Other Options Are Wrong: Side relief: relates to the side flank, not the end flank. Back/side rake: chip-flow angles, not clearance angles. Inclination angle: different standard parameter in ISO nomenclature. Common Pitfalls: Confusing “relief” (clearance) with “rake” (chip flow); they serve different purposes and are measured on different faces. Final Answer: end relief angle

Question 8

Cutting tool materials and capabilities: Identify the incorrect (wrong) statement among the following performance claims.

Accepted Answer

Introduction / Context: Different cutting tool materials offer distinct combinations of hot hardness, chemical stability, and toughness. Typical relative speed and temperature capabilities are well established in handbooks. The task is to spot the claim that is clearly incorrect. Given Data / Assumptions: Reference baseline: high-speed steel (HSS). Common categories: cemented carbides, ceramics (alumina-based, SiAlON), diamond/cBN, and cermets. Orders of magnitude and approximate ranges are acceptable. Concept / Approach: Ceramics exhibit exceptional hot hardness and can cut effectively at temperatures well above 600°C (often 1000–1200°C zone). Carbides typically allow several times HSS cutting speeds. Diamond is a superabrasive allowing extremely high speeds in nonferrous materials. Thus, a statement limiting ceramics to 600°C is wrong. Step-by-Step Solution: Review typical speed ratios: carbide ≈ 3–5× HSS; ceramics often 10–20× HSS in suitable applications.Assess temperature capability: ceramics remain hard > 1000°C.Identify the wrong claim → “only up to 600°C.” Verification / Alternative check: Tool vendor datasheets and machining handbooks report ceramic cutting temperatures commonly in the four-digit Kelvin range for hardened steels and cast irons. Why Other Options Are Not Wrong: Diamond hardness/speed superiority is broadly correct for nonferrous use. Ceramic speed range 10–20× HSS is a reasonable rule-of-thumb. Carbide 3–5× HSS is typical. Cermets indeed bridge performance between carbides and ceramics. Common Pitfalls: Taking every numerical multiplier literally; these are approximate and application-dependent, but the temperature limit in option (d) is clearly incorrect. Final Answer: Ceramic tools can withstand temperatures only up to 600°C.

Question 9

Centreless grinding kinematics: What is the typical maximum angular adjustment range available for the regulating (control) wheel relative to the grinding wheel/workrest?

Accepted Answer

Introduction / Context: In centreless grinding, the regulating wheel is inclined by a small angle to the workpiece axis. This angle controls the axial feed in through-feed grinding and affects stability and roundness. Machines provide a limited angular adjustment to tune process behavior. Given Data / Assumptions: Standard centreless grinder with tilting regulating wheel spindle. Usual industrial ranges for through-feed operations. Angle is modest (small degrees), not tens of degrees. Concept / Approach: The regulating wheel inclination is commonly adjustable from approximately zero up to about 8–10 degrees, sufficient to generate the desired axial thrust without compromising contact geometry or stability. Excessive angle would cause control loss or chatter. Step-by-Step Solution: Relate axial feed demand to tilt angle → small positive angle is adequate.Consult common practice → maximum adjustment around 10°.Therefore, choose 10° as the typical maximum. Verification / Alternative check: Machine manuals and textbooks cite ranges like 3–8° or up to roughly 10°, aligning with option (b). Why Other Options Are Wrong: 5° can be within range, but not a typical “maximum.” 15°/20°/30° are unusually large and impractical for stable grinding. Common Pitfalls: Confusing workrest blade angle with regulating wheel inclination; they are distinct setup parameters. Final Answer: 10°

Question 10

Gear milling cutters: Why is a standard set of eight form-relieved involute cutters supplied for each module or DP, and what does this set primarily accommodate?

Accepted Answer

Introduction / Context: When cutting spur gears with form-relieved involute gear cutters, the tooth form slightly varies with tooth count due to the involute generating geometry. To maintain correct profile across a range of tooth numbers, cutters are standardized into numbered sets for each module or diametral pitch (DP). Given Data / Assumptions: Spur gear milling on a horizontal or vertical mill using involute gear cutters. Each set contains eight cutters, numbered by tooth-count ranges. Module/DP is fixed for the set; pressure angle is also matched. Concept / Approach: Each cutter number corresponds to a range of teeth (e.g., 12–13, 14–16, …, rack). The slight profile differences ensure the milled gear approximates the true involute best for that tooth count range. Thus, the set accommodates variation in Z (number of teeth), not material, face width, or arbor size. Step-by-Step Solution: Fix module/DP and pressure angle.Select cutter number based on gear tooth count Z.Mill gear with appropriate cutter to achieve near-correct involute profile. Verification / Alternative check: Standard tables list eight numbered cutters per module/DP with corresponding Z ranges, including a “rack” range for very high teeth counts. Why Other Options Are Wrong: Material, face width, or arbor diameter are independent of involute form selection. Helical gears require different techniques (e.g., helical milling or hobbing), not simply a different cutter from the same set. Common Pitfalls: Mixing pressure angles or modules between cutter and gear; always match module/DP and pressure angle in addition to selecting the correct cutter number for Z. Final Answer: different number of teeth

Question 11

Snag grinding in manufacturing — what is it used for? In practical shop-floor operations, “snag” grinding refers to rough, heavy grinding on castings, forgings, or welds. What is the primary objective of snag grinding?

Accepted Answer

Introduction / Context: Snag grinding is a shop-floor term commonly used in foundries, fabrication shops, and heavy industries. Unlike precision grinding, where the goal is tight tolerance and surface finish, snagging focuses on rapid material removal to knock off gates, risers, fins, burrs, and weld spatter before subsequent finishing operations. Given Data / Assumptions: Work involves castings, forgings, or welded fabrications. The objective is speed and productivity, not fine tolerances. Typical tools include pedestal grinders, portable grinders, and large, hard-grade wheels. Concept / Approach: Grinding operations can be categorized into roughing and finishing. Snag grinding falls firmly into roughing. Wheel selections emphasize durability and stock removal rate (coarser grain, harder grade, open structure) rather than surface integrity or dimensional control. The feed pressure is high, and the contact time is short. Step-by-Step Solution: Identify the operation type: snagging is rough grinding.Define the goal: remove flash, gates, and heavy irregularities rapidly.Match wheel selection and technique to high material removal, not finish.Conclude that accuracy and finish are secondary; speed of removal is primary. Verification / Alternative check: Process routings typically list snagging before machining or precision grinding. After snagging, components move to milling, turning, or finish grinding to achieve the final dimensions and surface quality. Why Other Options Are Wrong: Precision surface finish and cylindrical accuracy are objectives of surface/cylindrical grinding, not snagging. Thread generation requires dedicated thread grinding or machining processes. Common Pitfalls: Using too soft a wheel for snagging causes rapid wheel wear. Targeting fine finishes at this stage wastes time and increases cost without benefit. Final Answer: To remove a considerable amount of metal quickly, with little regard for final accuracy

Question 12

Grinding wheel grade notation — which letters indicate a soft grade? In grinding wheel specifications (e.g., A 46 K 8 V), the grade letter denotes bond holding power. Which letter range corresponds to soft-grade wheels?

Accepted Answer

Introduction / Context: The ‘‘grade’’ in a grinding wheel specification represents the bond’s ability to retain abrasive grains. A ‘‘soft’’ grade releases dulled grains readily for self-sharpening, while a ‘‘hard’’ grade holds them longer. Understanding the letter ranges is crucial for selecting a wheel that balances wheel wear, cutting efficiency, and surface finish. Given Data / Assumptions: Standard alphabetical grade coding is used. Soft, medium, and hard are relative categories across A–Z. Operation and work material influence grade selection. Concept / Approach: Conventional practice classifies grades roughly as: soft A–H, medium I–P, and hard Q–Z. Softer grades are chosen for hard or tough work materials to avoid glazing, while harder grades suit softer or gummy materials to avoid rapid wheel breakdown. Step-by-Step Solution: Map letter ranges to qualitative grade levels.Recall: soft = A–H, medium = I–P, hard = Q–Z.Select the option that matches the soft range. Verification / Alternative check: Wheel catalogs from major manufacturers present tables where the grade letter increases from soft to hard; A–H are consistently designated as soft grades. Why Other Options Are Wrong: I–P and Q–Z correspond to medium and hard ranges, not soft. A–P spans both soft and medium and lacks precision. Common Pitfalls: Confusing abrasive hardness (e.g., Al2O3 vs SiC) with wheel grade; they are different attributes. Final Answer: A to H

Question 13

Oblique cutting mechanics — where does maximum chip thickness occur? In oblique cutting (tool cutting edge inclined to the feed direction), the chip does not form uniformly across the width. Where is the maximum chip thickness observed?

Accepted Answer

Introduction / Context: In metal cutting, orthogonal cutting assumes a straight cutting edge perpendicular to the cutting velocity, producing uniform chip thickness across width. Oblique cutting tilts the edge and introduces a more complex three-dimensional flow, altering chip thickness distribution. Given Data / Assumptions: Single-point tool with oblique cutting angle (inclination of the cutting edge). Steady cutting conditions and homogeneous work material. No built-up edge for simplicity. Concept / Approach: With obliquity, chip flow is helical and side-flow occurs. The resultant shear plane orientation and chip flow angle cause nonuniform chip load along the edge. As a result, the maximum chip thickness does not necessarily coincide with the geometric mid-width; it can shift toward the leading or trailing side depending on inclination and rake distribution. Step-by-Step Solution: Identify that oblique cutting breaks the symmetry of orthogonal cutting.Recognize chip flow angle causing side spread and nonuniform loading.Conclude that maximum chip thickness may not be at the middle; its position depends on obliquity and local geometry. Verification / Alternative check: High-speed imaging and chip morphology studies show chip thickness and contact pressure concentration away from the midspan in oblique cuts. Why Other Options Are Wrong: Claiming ‘‘always middle’’ ignores obliquity; asserting dependence only on tool material or only on angles oversimplifies—obliquity, rake variations, and feed direction jointly decide the distribution. Common Pitfalls: Applying orthogonal cutting intuition directly to oblique cutting; neglecting the side-flow component. Final Answer: It may not occur at the middle (location shifts due to obliquity)

Question 14

Machine tool guideways — common cross-sectional forms Guideways support and guide relative motion between machine tool elements. Which cross-sectional form(s) are used for guideways?

Accepted Answer

Introduction / Context: Guideways are precision mating surfaces that ensure straight, accurate motion in lathes, milling machines, shapers, and grinders. Their geometry is chosen to balance load capacity, stiffness, alignment, and manufacturability. Given Data / Assumptions: Common geometries: flat, V, and dovetail. Applications vary by machine type and load path. Scraped, ground, or coated bearing surfaces may be used. Concept / Approach: Flat ways are simple and offer good bearing area; V-ways provide self-alignment and lateral constraint; dovetail ways add retention and are common on small mills and slides. Designers pick a form based on anticipated loads, ease of manufacturing, and serviceability. Hence, more than one geometry is valid. Step-by-Step Solution: List typical way types: flat, V, dovetail.Map advantages: alignment (V), retention (dovetail), area (flat).Conclude that any may be used depending on the application. Verification / Alternative check: Machine tool catalogs reveal mixed forms: many engine lathes use V-and-flat combinations; milling tables use dovetail or box ways; grinders often use V-and-flat for precision. Why Other Options Are Wrong: Restricting to a single form ignores widespread industry practice. ‘‘Circular dovetail’’ is not a standard guideway form for linear motion. Common Pitfalls: Confusing slideway geometry with rolling-element linear guides; both are valid approaches but differ in construction. Final Answer: Any of these (flat, V, or dovetail) depending on design

Question 15

Cutting speed capability — HSS versus carbon steel tools Relative to plain carbon tool steels, high-speed steel (HSS) tools can normally operate at cutting speeds that are:

Accepted Answer

Introduction / Context: Tool material choice governs allowable cutting speed before excessive wear or softening occurs. High-speed steel (HSS) retains hardness at higher temperatures than plain carbon tool steel, enabling faster cutting and higher productivity. Given Data / Assumptions: Comparison at similar feeds and depths of cut. Uncoated, conventional tools. Typical machining of steels. Concept / Approach: HSS alloys (with W, Mo, Cr, V, Co) possess improved red hardness and toughness, so they tolerate higher temperatures at the cutting edge. Empirical practice shows HSS speeds are roughly 2–3 times those for carbon tool steels, while cemented carbides and ceramics are higher still. Step-by-Step Solution: Identify property difference: HSS has better hot hardness than carbon steel.Relate hot hardness to allowable cutting speed.Choose the realistic multiplier: 2–3 times higher for HSS. Verification / Alternative check: Machining handbooks list speed ranges showing HSS significantly above carbon steel, but far below carbides and ceramics. Why Other Options Are Wrong: ‘‘Lower’’ contradicts HSS advantage; ‘‘5–8’’ or ‘‘8–20 times’’ are more representative of carbide/ceramic jumps over carbon steel, not HSS. Common Pitfalls: Assuming coatings or carbide data when the question compares only HSS with carbon tool steel. Final Answer: 2 to 3 times higher

Question 16

Built-up edge (BUE) formation — which materials are most prone? Under low-to-moderate cutting speeds and small rake angles, built-up edge tends to form when machining which type of material?

Accepted Answer

Introduction / Context: Built-up edge (BUE) is an adhered layer of work material that forms on the rake face near the cutting edge. It cyclically grows and breaks off, degrading surface finish and dimensional accuracy. Knowing when BUE is likely helps select suitable speeds, tools, and coolants. Given Data / Assumptions: Low-to-moderate cutting speeds. Small rake angle, inadequate cutting fluid, or high friction conditions. Typical steels, aluminum, and ductile metals. Concept / Approach: Ductile materials tend to weld to the tool at elevated interface temperatures and high pressures. Adhesion and plastic flow promote BUE formation. Increasing speed, using sharper tools and positive rake, or applying effective coolants reduce BUE by lowering contact time and frictional sticking. Step-by-Step Solution: Relate BUE to adhesion and plastic flow of the work material.Identify that ductile metals (e.g., low carbon steel, aluminum) exhibit strong adhesion at the tool–chip interface.Conclude ductile materials are most prone to BUE under unfavorable cutting conditions. Verification / Alternative check: Increasing cutting speed or improving lubrication typically decreases BUE; surface finish improves correspondingly, which is observed widely in practice. Why Other Options Are Wrong: Brittle and very hard materials chip by fracture and are less adhesive; ‘‘tough’’ is vague without indicating ductility; sintered carbides are tool materials, not work materials being machined. Common Pitfalls: Confusing BUE with built-in chip breakers or with crater wear; they are different phenomena. Final Answer: Ductile material

Question 17

Chip morphology — continuous chip description Continuous chips produced during ductile cutting are often described as long coils with nearly uniform thickness along their length. Is this description accurate?

Accepted Answer

Introduction / Context: Chip type is a quick indicator of cutting mechanics and surface quality. Continuous chips typically arise when machining ductile materials at suitable speeds with sharp tools and adequate rake, often leading to good finish but chip disposal challenges. Given Data / Assumptions: Ductile work material (e.g., mild steel, aluminum). Sharp tool, positive rake, appropriate speed and feed. No significant built-up edge formation. Concept / Approach: Continuous chips form by plastic flow along a stable shear plane, producing a ribbon-like chip. Without chip breakers, the chip rolls into long coils or snarls. Thickness along the ribbon is approximately uniform because the shear conditions and undeformed chip thickness remain consistent during steady cutting. Step-by-Step Solution: Relate continuous chip to ductile flow and stable shear plane.Note that steady feed generates nearly constant undeformed chip thickness.Infer that the produced chip maintains near-uniform thickness, appearing as long coils. Verification / Alternative check: Shop observations show continuous helical chips on turning operations of ductile metals. Chip breakers are introduced to avoid safety hazards and tool damage due to long coils. Why Other Options Are Wrong: Brittle materials tend to form discontinuous or segmented chips; cast irons usually break into small segments due to graphite flakes; rake angle variations influence chip curl but not the fundamental definition. Common Pitfalls: Assuming absolutely constant thickness; in reality, minor variations occur, but the description ‘‘long coils with the same thickness’’ is an accepted practical characterization. Final Answer: Agree

Question 18

Twist drill geometry — typical chisel edge angle For standard twist drills used on steels, the chisel edge angle is generally taken in the range:

Accepted Answer

Introduction / Context: The chisel edge of a twist drill is the web intersection at the drill point. Its angle affects thrust force and chip initiation near the drill axis. Recognizing typical ranges helps in sharpening and selecting drills for different materials. Given Data / Assumptions: Standard two-flute twist drill. General-purpose drilling of steels. Conventional point geometries without split points or special grinds. Concept / Approach: Typical practice uses a chisel edge angle in the range of about 120°–135°. Larger chisel angles (with proper web thinning) help reduce rubbing and thrust; smaller angles can increase axial force. Point angle (often 118°–135°) is related but distinct from the chisel edge angle; both define the drill’s cutting behavior. Step-by-Step Solution: Differentiate between point angle and chisel edge angle.Recall the common chisel edge range used on steels.Select 120° to 135° as the standard range. Verification / Alternative check: Toolroom references show chisel edge angles commonly paired with 118°–135° point angles, with web thinning to reduce thrust and improve centering. Why Other Options Are Wrong: Other ranges do not reflect mainstream practice for general-purpose twist drills and would lead to poor cutting or excessive thrust. Common Pitfalls: Confusing chisel edge angle with point angle; they influence different aspects of the drill tip geometry. Final Answer: 120° to 135°

Question 19

Boring versus drilling — primary purpose of boring Compared with drilling, what is the main purpose of a boring operation on a previously made hole?

Accepted Answer

Introduction / Context: Drilling initiates a hole; boring refines it. In process planning, boring is used after drilling or casting to achieve an accurate diameter, better roundness, alignment, and improved surface finish, especially on precision bores such as bearing seats. Given Data / Assumptions: A pre-existing hole from drilling, casting, or core. Single-point boring bar in a lathe, boring mill, or machining center. Need for both size control and geometric accuracy. Concept / Approach: Boring removes additional material from the bore wall to reach the target size and straightness. Unlike reaming (mostly sizing/finishing with small allowance), boring can correct location errors, taper, and out-of-round conditions while enlarging to specification. Step-by-Step Solution: Identify starting condition: an existing hole.Define action: remove material from the bore to increase diameter.Outcome: improved size, straightness, and finish. Verification / Alternative check: Inspection after boring typically shows improved cylindricity and alignment compared to the as-drilled hole. Why Other Options Are Wrong: Drilling is for solid stock; finishing without enlargement is more akin to reaming/honing; purely ‘‘correcting’’ without enlargement is uncommon because some stock must be removed to correct errors. Common Pitfalls: Confusing boring with reaming or honing; each has specific stock allowances and achievable tolerances. Final Answer: To enlarge the existing hole (and improve accuracy/finish)

Question 20

Chip thickness profile in milling — down (climb) milling In down milling (climb milling), how does the instantaneous chip thickness vary from entry to exit of the cut?

Accepted Answer

Introduction / Context: Milling chip load distribution affects surface finish, tool wear, and machine dynamics. Understanding how chip thickness evolves during the tooth engagement helps in selecting feeds, cutter geometry, and climb versus conventional strategies. Given Data / Assumptions: Peripheral milling with a standard helical end mill or slab mill. Down (climb) milling configuration: cutter rotation assists the feed direction. Rigid setup and proper backlash control. Concept / Approach: In down milling, the cutting tooth first meets the work at maximum uncut chip thickness and exits at near-zero thickness. This reduces rubbing at the exit and can improve surface finish and tool life, provided machine backlash and workholding are adequate. Conventional (up) milling has the opposite profile. Step-by-Step Solution: Define chip thickness h(theta) based on entry/exit angles.For down milling, entry angle corresponds to maximum h; exit angle tends to zero h.Conclude that chip thickness decreases from maximum at entry to minimum at exit. Verification / Alternative check: Cutting force measurements show peak forces near entry in climb milling, tapering off toward exit as h diminishes. Why Other Options Are Wrong: Option (a) describes up milling; uniform thickness does not occur in peripheral milling; randomness is not a defining feature and depends on dynamics, not geometry. Common Pitfalls: Attempting climb milling on machines with significant backlash can cause work pull-in; modern CNCs mitigate this with preloaded screws. Final Answer: Maximum at the beginning and minimum at the end

Production Engineering Questions