Question 1

Measuring cutting force at the tool–chip interface In metal cutting operations (turning, milling, drilling), which instrument is specifically used to measure the cutting force(s) acting at the cutting edge during machining trials or process monitori…

Accepted Answer

Introduction / Context: Accurate measurement of cutting forces is fundamental in machining science because these forces govern power consumption, tool wear, surface finish, and vibration. Process developers and researchers rely on dedicated instruments to quantify forces in turning, milling, and drilling so that speeds, feeds, and tool geometries can be optimized. Given Data / Assumptions: Conventional metal cutting (orthogonal or oblique) with standard tools. Need to measure tangential, radial, and feed components of force. Laboratory or shop-floor test setup is available for instrumentation. Concept / Approach: A machining dynamometer is designed to resolve forces along defined axes. Turning dynamometers typically measure two or three components, while milling dynamometers measure multiple components via piezoelectric or strain-gage transducers. The output is calibrated to display force directly. Other instruments like wattmeters or pyrometers indicate power or temperature, not force, and hydrometers measure fluid density. Step-by-Step Solution: Identify the physical quantity required: cutting force components.Match the quantity to the correct instrument: a dynamometer converts mechanical load into an electrical signal proportional to force.Select the option that explicitly measures cutting forces in machining: dynamometer. Verification / Alternative check: Standard machining texts and tool catalogs specify piezoelectric quartz dynamometers or strain-gage ring dynamometers for force measurement in turning, drilling, and milling experiments. Why Other Options Are Wrong: Wattmeter: measures electrical power, not individual force components.Hydrometer: measures liquid density; irrelevant to machining forces.Pyrometer: measures high temperature (tool/work/chip), not force.Strain gauge adhesive only: adhesive is a component, not a complete calibrated force-measuring instrument. Common Pitfalls: Inferring force from spindle power alone is inaccurate because it includes losses and cannot separate feed/radial components. Proper fixturing and calibration are essential to avoid cross-sensitivity and drift in dynamometer readings. Final Answer: Dynamometer

Question 2

Design basis for a screw-cutting lathe feed gearbox In a screw-cutting engine lathe, the feed gearbox (or Norton/quick-change gearbox) is typically laid out to produce a series of feeds and thread pitches following which mathematical progression?

Accepted Answer

Introduction / Context: A quick-change feed gearbox lets machinists select many feed rates and thread pitches quickly. The arrangement of gears determines how uniformly the available settings are distributed, which impacts finish, tool life, and flexibility. Given Data / Assumptions: Conventional screw-cutting lathe with a Norton-style or similar gearbox. Objective: evenly spaced, practical feed steps over a range. No special electronic variable-speed drives are assumed. Concept / Approach: Gearbox design commonly uses a geometric progression for feed steps. With geometric progression, each step is a constant ratio from the previous one, yielding uniform percentage changes across the range. This is advantageous for maintaining consistent changes in surface finish and chip load when stepping up or down feeds. Arithmetic progression would produce equal absolute differences, which is less suitable over wide ranges. Step-by-Step Solution: Define the need: a broad, usable range of feeds and pitches.Apply equal ratio stepping so each successive feed differs by a constant factor.Conclude that gear selection follows a geometric progression. Verification / Alternative check: Lathe gear charts and design literature routinely present feeds and threads in geometric or near-geometric series (e.g., R20-like series), ensuring practical spacing across low to high feeds. Why Other Options Are Wrong: Arithmetic progression: causes overly fine steps at one end and coarse at the other.Harmonic progression: not used for feed step planning.No defined or random series: impractical for standardized machining results. Common Pitfalls: Assuming thread pitches can be arbitrarily generated without considering lead screw pitch and change gear ratios. Proper series selection simplifies operator use and documentation. Final Answer: Geometric progression

Question 3

Tailstock set-over for straight-through taper turning A cylindrical workpiece is to be turned to a uniform taper along its entire center-to-center length. If the large and small diameters are D and d respectively, what tailstock set-over is required…

Accepted Answer

Introduction / Context: Taper turning between centers can be achieved by offsetting the tailstock. This method tilts the work axis relative to the lathe axis, producing a linear change in radius along the workpiece length. Knowing the correct set-over is crucial to obtain the target diameters. Given Data / Assumptions: Large diameter at one end: D. Small diameter at the other end: d. Taper is uniform over the full center distance (effective turned length equals the distance between centers). Small offset angles (typical for taper turning) are assumed. Concept / Approach: For a full-length uniform taper produced by tailstock set-over, the radial change from one end to the other equals the change in radius, which is (D - d)/2. The tailstock set-over equals this radius difference because the work axis must be shifted laterally by exactly half the total change in diameter to align the conical surface with the tool path. Step-by-Step Solution: Define diameter change across the length: ΔD = D - d.Convert to radius change: ΔR = ΔD / 2.For taper over full length between centers, required lateral set-over equals the change in radius: set-over = (D - d) / 2. Verification / Alternative check: Graphic construction of the axis shift shows that when the work axis is offset by ΔR, the tool tracing parallel to the lathe axis generates the required cone from radius R1 to R2 along the whole length. Why Other Options Are Wrong: (D - d): doubles the required set-over; would overshoot the taper.(D + d)/2: unrelated to taper geometry.(D^2 - d^2)/(2L): relates to slope if L is included, but not the simple full-length set-over value.tan^-1[(D - d)/L]: this is an angle; the question asks for linear set-over. Common Pitfalls: Confusing set-over distance with taper angle; neglecting the fact that set-over equals radius change for full-length tapers. Final Answer: (D - d) / 2

Question 4

Tool material used in ultrasonic machining (USM) In ultrasonic machining, which tool material is commonly employed because the tool must be tough and ductile enough to withstand high-frequency vibration and transmit abrasive action effectively?

Accepted Answer

Introduction / Context: Ultrasonic machining (USM) removes material by micro-chipping under abrasive slurry while a tool vibrates at ultrasonic frequency. The tool material must transmit vibrations, resist fatigue, and shape easily to the negative of the cavity to be produced. Given Data / Assumptions: Abrasive slurry: typically silicon carbide, boron carbide, or aluminum oxide in water. Frequency: roughly 20–40 kHz with small amplitudes. Work materials: hard/brittle (glass, ceramics, carbides). Concept / Approach: Ductile, relatively soft metals like brass and copper are preferred tool materials in USM. They damp undesirable stresses, are easy to machine into intricate shapes, and survive the cavitation-like impacts of abrasive grains. Extremely hard tool materials (e.g., carbide) are unnecessary and can be brittle under cyclic loading; diamond is used as abrasive, not as bulk tool in USM. Step-by-Step Solution: Recognize USM removes work by abrasive hammering, not by tool cutting edge.Select a tool that is tough, ductile, and easily formable: brass or copper.Confirm that the tool slowly wears while faithfully transmitting vibrations to the slurry. Verification / Alternative check: USM process descriptions consistently list soft ductile metals (brass, copper) and sometimes mild steel or Monel as tool materials, paired with hard abrasives like boron carbide. Why Other Options Are Wrong: Tungsten carbide and diamond: unnecessarily hard and brittle as bulk tools in USM; diamond is the abrasive in other contexts.Stainless steel/HSS: usable in some cases, but brass or copper are standard due to superior formability and damping. Common Pitfalls: Assuming the tool must be harder than the work as in cutting; in USM, the abrasive does the cutting while the tool shapes and delivers energy. Final Answer: Brass or copper

Question 5

Oblique cutting and surface generation Consider oblique cutting (tool cutting edge inclined to the direction of cutting). Is it true that the tool may or may not generate a surface parallel to the tool face, depending on the inclination and geometry?

Accepted Answer

Introduction / Context: Machining can be analyzed as orthogonal or oblique cutting. In oblique cutting, the cutting edge is inclined, altering chip flow direction and the kinematics of the generated surface. Given Data / Assumptions: Tool has nonzero inclination angle (lambda) with respect to cutting velocity. Work material and feeds are typical; no special chip-control grooves considered. Surface generation depends on effective rake and edge orientation. Concept / Approach: Unlike orthogonal cutting where the cutting edge is perpendicular to the cutting direction, oblique cutting deflects chip flow sideways. The geometry can yield a generated surface that is not strictly parallel to the tool face; it depends on rake, inclination, and approach angles. Thus, it is correct to say the tool may or may not generate a surface parallel to the face. Step-by-Step Solution: Recognize oblique cutting involves a nonzero inclination angle.Acknowledge that chip flow angle and surface texture orientation change with geometry.Conclude that surface parallelism with the tool face is not guaranteed. Verification / Alternative check: Machining theory shows the chip flow angle eta and the normal rake governing chip direction; graphical kinematics confirm nonparallel outcomes are common in oblique cutting. Why Other Options Are Wrong: “No”: contradicts geometric reality of oblique cutting.Material-specific or rake-specific qualifiers are unnecessary; geometry alone dictates the relationship. Common Pitfalls: Assuming orthogonal cutting relations apply directly to oblique cutting; overlooking the role of inclination angle in surface generation and chip disposal. Final Answer: Yes

Question 6

Chip type when machining mild steel During turning of mild steel under normal conditions (adequate rake and speed), what type of chip is most commonly produced?

Accepted Answer

Introduction / Context: Chip morphology depends on material ductility, cutting speed, rake, and lubrication. Recognizing typical chip forms helps diagnose cutting issues and choose chip control features. Given Data / Assumptions: Work material: mild steel (ductile). Tool: standard positive rake HSS/carbide. Cutting speed and feed are within normal ranges with coolant. Concept / Approach: Ductile materials like mild steel usually produce continuous chips due to stable plastic flow ahead of the tool. Depending on speed and lubrication, a built-up edge may form intermittently, but the underlying chip type remains continuous. Discontinuous chips are typical of brittle materials or very low speeds/large feeds. Segmented adiabatic shear chips occur at very high speeds in difficult alloys. Step-by-Step Solution: Identify the material as ductile → favors continuous flow.Consider normal speed, rake, and coolant → promotes continuous chips.Select “Continuous” as the predominant chip type for mild steel. Verification / Alternative check: Textbook chip classification and shop observations consistently show continuous chips for steels of low to medium carbon when tooling and speeds are appropriate. Why Other Options Are Wrong: Discontinuous chips: associated with brittle materials or extreme conditions.Continuous with BUE only: BUE may occur, but the chip type is still continuous; the option over-specifies.Segmented adiabatic shear: typical in high-speed machining of titanium/nickel alloys.No chip: not applicable to conventional cutting. Common Pitfalls: Confusing presence of BUE with discontinuous chips; BUE is an interface phenomenon, not a chip-class change. Final Answer: Continuous

Question 7

Definition of chamfering on a lathe Which statement best defines the chamfering operation performed on a workpiece at the lathe or during secondary finishing?

Accepted Answer

Introduction / Context: Chamfering is widely used to deburr sharp edges, aid assembly, and improve aesthetics. It is a simple but important finishing operation in machining and fabrication. Given Data / Assumptions: External edges on shafts, pins, and blocks often require a 30–45 degree chamfer. Chamfers can be produced by turning tools, chamfer mills, or hand tools. Objective: remove sharp corner, produce clean lead-in. Concept / Approach: A chamfer is a straight, flat, angled surface at an edge. On a lathe, a simple angular infeed with a turning tool creates the chamfer at the end face/outer diameter junction. It is distinct from knurling (pattern), undercutting/necking (narrow diameter reduction), counterboring (enlarging a hole with a flat bottom), and countersinking (conical recess). Step-by-Step Solution: Identify the goal: remove sharp edge and create an angled lead-in.Select the operation that forms an external beveled surface: chamfering.State the correct definition: bevelling the extreme end of a workpiece. Verification / Alternative check: Engineering drawing standards specify chamfer dimensions (e.g., 2 x 45°) to indicate size and angle, confirming the operation’s nature. Why Other Options Are Wrong: Embossing pattern: describes knurling, not chamfering.Necking: reduces diameter locally; not a bevel.Counterboring/countersinking: internal hole features, not external edges. Common Pitfalls: Confusing chamfers with radii; a radius is curved, whereas a chamfer is a flat, straight bevel. Ensure burrs are removed fully to prevent assembly issues. Final Answer: Bevelling the extreme end of a workpiece

Question 8

Milling direction terminology When the milling cutter rotates in the same direction as the feed motion of the workpiece (chip thickness starts maximum and decreases), what is this operation called?

Accepted Answer

Introduction / Context: Milling direction affects chip thickness profile, cutting forces, surface finish, and fixture requirements. Choosing up or down milling is a key process decision, especially on machines with or without backlash compensation. Given Data / Assumptions: Standard horizontal or vertical milling setup. Properly adjusted machine with minimal backlash (or CNC with compensation). Work and cutter engagements are typical. Concept / Approach: In down (climb) milling, the cutter rotation matches the feed direction. Chip thickness starts at a maximum and reduces to nearly zero, often giving better surface finish and tool life, provided backlash is controlled and the work is rigidly clamped. In up (conventional) milling, the cutter rotates against the feed and chip starts from zero thickness, increasing to maximum at exit. Step-by-Step Solution: Determine relative directions: cutter rotation and table feed are the same → down milling.Consider benefits: improved finish, lower rubbing at entry, reduced work hardening.State correct name: down milling (climb milling). Verification / Alternative check: Process diagrams in machining texts illustrate chip thickness progression for up vs. down milling, matching the stated definition. Why Other Options Are Wrong: Up milling: feed opposite rotation; incorrect direction.Face/End milling: describe cutter orientation, not direction of milling.Slotting: a specific operation, not a direction convention. Common Pitfalls: Using down milling on worn machines with backlash can cause part “pull-in.” Always ensure rigid clamping and backlash control. Final Answer: Down milling (climb milling)

Question 9

Grinding of soft materials: limiting factor Why are very soft, ductile materials generally not ground economically with conventional vitrified wheels in production settings?

Accepted Answer

Introduction / Context: Grinding is a precision abrasive process. Its effectiveness depends on maintaining open chip spaces between abrasive grains so chips can be removed without smearing or glazing the wheel. Given Data / Assumptions: Conventional vitrified-bonded aluminum oxide or silicon carbide wheels. Work materials: soft, ductile metals (e.g., pure aluminum, soft copper). Normal wheel grades and coolants. Concept / Approach: Soft ductile chips tend to plastically smear and adhere to abrasive grains, quickly filling the wheel's intergranular spaces. This phenomenon is called wheel loading or clogging. Loaded wheels rub instead of cut, causing burn, poor finish, and dimensional error, and require frequent dressing—making the process uneconomical compared to alternative methods (e.g., turning with sharp tools or using specialized nonloading wheels). Step-by-Step Solution: Recognize ductile chips deform and smear under pressure.Identify that chips occupy chip pockets and stick to grain tips → wheel loading.Conclude grinding becomes inefficient and costly due to frequent dressing downtime. Verification / Alternative check: Process troubleshooting charts list “loading” as a dominant issue in grinding soft metals; recommended remedies include open-structure wheels, coarser grits, softer grades, and aggressive coolants. Why Other Options Are Wrong: Excessive temperature: can occur, but loading is the primary economic limitation.Rapid wheel wear: less typical than glazing/loading on soft metals.Low stiffness: not a general property of soft metals workpieces; many are adequately rigid.Coolant application: feasible; not the core obstacle. Common Pitfalls: Using fine, hard, closed-structure wheels on soft metals worsens loading. Choose coarse, open structures and consider waxy lubricants or special wheel bonds for aluminum. Final Answer: Frequent wheel clogging (loading) occurs

Question 10

Effect of small nose radius on tool performance Considering turning with a single-point tool, what is a typical consequence of using a very small nose radius at the cutting tip?

Accepted Answer

Introduction / Context: Nose radius is a key geometry parameter on turning tools. It influences surface finish, edge strength, and cutting forces. Choosing too small or too large a radius has trade-offs that directly affect tool life and surface quality. Given Data / Assumptions: Standard turning on steels with carbide or HSS tools. Feeds in common finishing ranges. No special edge honing beyond typical prep. Concept / Approach: A very small nose radius creates a sharp point with limited support behind the cutting edge. This increases stress concentration at the tip and makes the edge susceptible to micro-chipping, especially under intermittent cutting or hard inclusions. The result is accelerated wear and reduced tool life. Moderate radii distribute cutting load and improve finish up to a limit; excessively large radii can induce chatter at light feeds. Step-by-Step Solution: Relate nose radius to edge strength: smaller radius → higher stress concentration.Expect chipping at the tip under real cutting disturbances.Infer decreased tool life and possible deterioration of surface finish due to micro-chipping. Verification / Alternative check: Tooling handbooks recommend selecting nose radius proportional to feed (e.g., radius roughly 1/3 to 1/2 of feed per rev) to balance finish and edge strength, avoiding extremely small radii. Why Other Options Are Wrong: Increases tool life: opposite of typical outcome with very small radii.Decreases life only due to rubbing: rubbing is less relevant; the issue is edge strength.Eliminates stress and heat: incorrect; stress concentration increases.Improves finish at all feeds: too small a radius can leave torn surfaces at higher feeds. Common Pitfalls: Assuming smallest radius always gives sharpness and best finish; without support, edge fractures and finish degrades. Match radius to feed and rigidity. Final Answer: Produces chipping and decreases tool life

Question 11

Parting-off tool geometry in turning  In lathe operations, the width of the cutting edge (blade) of a parting-off tool is typically selected within which standard range to balance chip flow, rigidity, and power requirement?

Accepted Answer

Introduction / Context: Parting-off (cut-off) is a common lathe operation used to separate a finished component from bar stock. Choosing the correct blade width is essential for process stability, chip evacuation, surface finish, and tool life. Too wide increases cutting power and heat; too narrow risks chatter and tool breakage. Given Data / Assumptions: General-purpose engine lathe with standard toolholders. Conventional HSS or carbide-tipped parting tools for steels and nonferrous alloys. Industrial practice and catalog ranges for typical parting blades. Concept / Approach: The blade width determines chip cross-section and stiffness. Common shop practice uses narrower blades for small diameters and softer materials, and wider blades for larger diameters requiring greater rigidity. Standard commercial blades for general work center around a few millimeters up to about a centimeter. The widely cited practical range is approximately 3 to 12 mm for typical lathes and work sizes. Step-by-Step Solution: Relate cutting force to chip cross-section: wider blade → larger chip area → higher force.Relate rigidity to width: wider blade → stiffer but more power needed; balance is required.Survey typical catalog sizes and shop norms → commonly 3–12 mm covers most standard turning jobs.Therefore, select the standard range 3 to 12 mm as the best answer. Verification / Alternative check: Tool catalogs list parting blades in roughly this range for general-purpose applications; very small precision lathes use narrower inserts, while heavy parting on large diameters may use special wider blades outside everyday practice. Why Other Options Are Wrong: 5 to 20 mm (B) and 8 to 30 mm (C) are skewed too wide for typical lathes; they imply excessive power and slot width. 15 to 40 mm (D) is unrealistic for standard parting operations. 2 to 6 mm (E) is too narrow to represent the full practical spread across general-purpose work. Common Pitfalls: Using a blade that is too wide for small parts, causing chatter due to excessive force; or using too narrow a blade on large diameters, causing deflection and breakage. Ignoring the machine's power and rigidity limits is another common mistake. Final Answer: 3 to 12 mm

Question 12

Relating tool geometry across processes  The rake angle of a single-point cutting tool in turning corresponds to which geometric angle on a twist drill used in drilling?

Accepted Answer

Introduction / Context: Cutting geometry concepts repeat across machining processes. In turning, rake angle controls chip flow and cutting forces. In drilling, chip flow is governed by the drill's flute helix. Understanding the correspondence helps transfer intuition between operations. Given Data / Assumptions: Single-point turning tool with defined rake face. Standard twist drill with helical flutes and cutting lips. Comparative mapping of cutting geometry terms. Concept / Approach: Rake angle is the angle that facilitates chip flow off the cutting edge. On a twist drill, the equivalent function is served by the helix angle of the flutes, which determines chip flow direction and effective rake along the cutting lips. Other drill angles (point angle, chisel edge angle, lip clearance) serve different functions. Step-by-Step Solution: Identify the function of rake: reduce cutting resistance, guide chip flow.Find the drill feature that controls chip flow similarly → flute helix angle.Conclude helix angle best corresponds to rake angle in turning. Verification / Alternative check: Drill design references treat helix as providing positive rake along the lips; altering helix angle changes chip evacuation and cutting forces analogous to changing rake in turning. Why Other Options Are Wrong: Lip clearance angle affects relief behind the cutting edge, not chip flow direction. Point angle defines included tip angle and penetration characteristics. Chisel edge angle addresses the web at the tip (extruding action, not primary rake). Margin relief angle concerns friction with the hole wall. Common Pitfalls: Assuming point angle equals rake; overlooking that effective rake along drill lips is a function of helix and point geometry together. Final Answer: helix angle

Question 13

Milling operations taxonomy  What do we call the milling operation in which multiple cutters are mounted on a common arbor to machine several surfaces of a workpiece simultaneously?

Accepted Answer

Introduction / Context: Milling offers many variants tailored to geometry and productivity. When the aim is to machine several surfaces in a single pass for high throughput, special cutter arrangements are used. Given Data / Assumptions: Horizontal milling machine with arbor-mounted cutters. Multiple cutters selected for the required faces or slots. Concept / Approach: Gang milling mounts more than one cutter on the same arbor so that multiple features are produced in one traverse. This improves productivity and ensures relative dimensional control between features. Step-by-Step Solution: Identify goal: machine several surfaces in one pass.Match process: multiple cutters on an arbor → gang milling.Confirm distinction from related terms. Verification / Alternative check: Manufacturing handbooks illustrate gang cutter stacks with spacers to create complex profiles in one operation. Why Other Options Are Wrong: Profile milling uses a single form cutter or end mill to trace shapes. Saw milling uses a thin cutter mainly for slots/parting. Helical milling refers to generating helical features (e.g., helical gears). Straddle milling uses two side milling cutters to machine opposite sides simultaneously, not multiple different surfaces. Common Pitfalls: Confusing straddle milling (two sides) with gang milling (many surfaces/features). Final Answer: gang milling

Question 14

Tool wear mechanisms in turning  Crater wear on the rake face of a cutting tool primarily results in which of the following effects on the metal cutting process?

Accepted Answer

Introduction / Context: Tool wear modes include flank wear and crater wear. Crater wear forms on the rake face due to diffusion, abrasion, and adhesion with the hot chip. Recognizing its effects helps schedule tool changes and choose cutting parameters. Given Data / Assumptions: Continuous cutting of steels with HSS or carbide tools. Elevated interface temperatures and chip-tool contact. Concept / Approach: Crater wear modifies rake geometry, increasing the effective friction and altering chip flow. This raises cutting forces and temperature. The tool cross-section near the cutting edge is reduced, weakening the edge and increasing risk of chipping or breakage. Step-by-Step Solution: Crater forms on rake face → reduces effective rake angle.Lower effective rake → higher shear deformation and friction → higher forces and heat.Material removal of the rake face → structurally weak edge → tool failure risk increases. Verification / Alternative check: Tool life criteria often specify a maximum crater depth for carbide tools because performance degrades rapidly beyond that threshold. Why Other Options Are Wrong: Each individual effect (A, B, C) occurs; thus the most complete answer is (D) all of these. Common Pitfalls: Monitoring only flank wear and ignoring crater depth; misattributing rising power draw to work material instead of tool wear. Final Answer: all of these

Question 15

Grinding wheel service measures  In production grinding, the “tool life” of a grinding wheel is best defined as the time interval between which two recurring maintenance actions?

Accepted Answer

Introduction / Context: Unlike single-point tools, grinding wheels consist of many abrasive grains that dull and dislodge. Wheel maintenance restores cutting ability. Understanding the correct measure of a wheel's useful period aids process control. Given Data / Assumptions: Conventional vitrified or resin-bonded wheels. Normal shop practice: truing for geometry; dressing for sharpness/open structure. Concept / Approach: Dressing exposes fresh, sharp grains and opens clogged pores. The interval between dressings represents the period during which the wheel cuts effectively before glazing or loading reduces performance. Thus wheel “tool life” is commonly the time between dressings under stated conditions. Step-by-Step Solution: Identify maintenance types: truing (restore geometry) vs dressing (restore sharpness).Relate cutting ability to dressing frequency.Define wheel tool life as time between successive dressings. Verification / Alternative check: Process sheets specify dressing frequency to maintain surface finish and size control; production logs track time or pieces between dressings as a performance metric. Why Other Options Are Wrong: Regrinding (A) and balancing (B) are not routine short-interval actions defining cutting ability. 1 mm wear (D) is not a standard universal criterion; wear rate depends on many factors. Truing alone (E) restores geometry but not necessarily cutting capacity without dressing. Common Pitfalls: Confusing truing with dressing; overdressing leading to excessive wheel consumption; underdressing causing burn and chatter. Final Answer: two successive wheel dressings

Question 16

Centerless plunge (infeed) grinding parameters  For plunge grinding on a centerless grinder, the process requires very ______ work (regulating wheel) speed to achieve stability and dimensional control.

Accepted Answer

Introduction / Context: In centerless grinding, through-feed and infeed (plunge) modes behave differently. Infeed grinding is used for shoulders, grooves, and profiles, where the workpiece does not translate axially past the wheel. The regulating wheel controls rotational speed and support. Given Data / Assumptions: Plunge (infeed) centerless configuration; no axial feed of the work. Work is supported by a work-rest blade and rotated by the regulating wheel. Concept / Approach: For stability and to prevent chatter, the work rotational speed is intentionally kept relatively low in plunge grinding. The grinding wheel operates at high surface speed, while the regulating wheel sets a slow rotational speed adequate for grinding forces and cooling without inducing lobing or instability. Step-by-Step Solution: Identify mode: infeed (no axial through-feed), requiring rotational support only.Set regulating wheel speed low to maintain control and avoid thermal damage.Conclude: plunge grinding uses very low work speed. Verification / Alternative check: Machine setup guides list typical regulating wheel surface speeds that are much lower than the grinding wheel for plunge operations, emphasizing slow, steady rotation. Why Other Options Are Wrong: High (A) risks chatter and lobing. Moderate/higher than through-feed (C) contradicts usual practice. Zero (D) is impossible; rotation is required for roundness. Variable sinusoidal (E) is not used; speed should be steady. Common Pitfalls: Setting excessive work speed causing chatter; insufficient support angle; incorrect work-rest blade height producing out-of-round parts. Final Answer: low

Question 17

Defining and assessing machinability  Which set of practical indicators is commonly considered together when evaluating the machinability of an engineering material?

Accepted Answer

Introduction / Context: Machinability expresses how easily a material can be machined to the desired finish and accuracy. It is not a single property but a practical assessment derived from several measurable indicators under specified conditions. Given Data / Assumptions: Comparable cutting conditions (tool, speed, feed, depth of cut) across materials. Objective measures available: forces, tool wear, chip form, power, and surface finish. Concept / Approach: Good machinability means lower cutting forces/power, longer tool life, and favorable chip forms (continuous without BUE). Shear angle trends also indicate ease of shearing. Considering multiple factors gives a robust evaluation rather than relying on a single metric. Step-by-Step Solution: Record cutting forces/power → lower values suggest easier cutting.Measure tool life → longer life at given conditions implies better machinability.Observe chip type and shear angle → favorable chip flow and larger shear angle indicate improved machinability.Combine indicators for a comprehensive rating. Verification / Alternative check: Machinability rating charts compare materials using normalized baselines (e.g., free-machining steel) considering several indicators. Why Other Options Are Wrong: Each single indicator (A, B, C) is valid but incomplete; relying on surface roughness alone (E) ignores tool wear, power, and chip control. Common Pitfalls: Comparing machinability across different tools or parameters; ignoring coolant effects; failing to define the measurement method. Final Answer: all of these

Question 18

Twist drill geometry for effective cutting  For a standard twist drill, should the lip clearance angle be larger at the circumference and decrease towards the center (chisel edge) to balance cutting and strength?

Accepted Answer

Introduction / Context: The lip (relief) clearance angle on a twist drill prevents rubbing behind the cutting edge. Its distribution from periphery to center affects cutting efficiency, heat generation, and tool strength. Given Data / Assumptions: Standard jobber-length twist drill geometry. Moderate feeds and speeds on common engineering materials. Concept / Approach: At the drill center, cutting speed approaches zero. Excessive relief there would weaken the web and cutting edge. Therefore, drills are ground with greater clearance at the periphery where speed is highest and rubbing risk is greater, and progressively smaller clearance towards the center to maintain strength and avoid chattering of the chisel edge. Step-by-Step Solution: Recognize speed distribution: v = omega * radius; near center, v ~ 0.Set relief higher at periphery to reduce rubbing at high surface speed.Reduce relief towards center to support the thin web and chisel area.Conclusion: the lip clearance angle decreases towards the center. Verification / Alternative check: Drill grinding charts show typical relief angles larger at the margin and smaller near the web; split-point and web-thinning geometries further optimize central cutting. Why Other Options Are Wrong: No (B) contradicts standard practice; (C) and (D) impose unneeded material-specific restrictions; (E) constant relief is not ideal due to varying cutting speeds across the radius. Common Pitfalls: Over-relieving the lips near the center causing weak chisel edge; insufficient relief at the periphery causing rubbing and heat. Final Answer: Yes

Question 19

Measuring tool life in production  In practical machining, tool life may be expressed using several equivalent measures under stated conditions. Which of the following are accepted ways to quantify tool life?

Accepted Answer

Introduction / Context: Tool life is central to cost, quality, and scheduling. Because processes and parts differ, industry uses several practical measures to define when a tool has reached its end of life under specified criteria. Given Data / Assumptions: Consistent cutting parameters and a defined end-of-life criterion (e.g., maximum wear or finish limit). Production environment where parts count, time, and volume can be tracked. Concept / Approach: Tool life can be captured as: (1) number of parts produced per sharpening or insert edge; (2) cutting time until reaching a wear criterion; or (3) total volume of metal removed per edge. Each correlates with cost-per-part and scheduling. Step-by-Step Solution: Define a wear or finish limit (e.g., flank wear width).Track pieces produced, or run time, or volume removed until the limit is reached.Any of these metrics expresses tool life when tied to the defined limit. Verification / Alternative check: Standards and textbooks accept multiple life metrics; Taylor's tool life equation commonly uses time, but production uses parts count or volume for convenience. Why Other Options Are Wrong: Only flank wear width (E) is a criterion, not itself an operational metric unless linked to time, pieces, or volume. Common Pitfalls: Comparing tool life across different metrics without normalization; failing to note the end-of-life criterion; ignoring effects of regrinds/edge indexing. Final Answer: all of the above

Question 20

Determinants of shear angle in continuous chip formation  During orthogonal cutting that produces continuous chips, which parameters primarily influence the value of the shear angle?

Accepted Answer

Introduction / Context: The shear angle governs chip thickness, cutting force, and temperature in metal cutting. Understanding what affects it enables better selection of feeds, tool geometry, and cutting strategy for surface finish and productivity. Given Data / Assumptions: Orthogonal cutting model with continuous chip formation. Work material is ductile; no segmentation or built-up edge at chosen parameters. Concept / Approach: According to classic cutting mechanics (e.g., Merchant-type relations), shear angle depends on geometry and deformation, notably the rake angle, uncut chip thickness (set by feed and depth), and friction. Chip thickness ratio directly reflects shear angle. Thus feed (which sets uncut chip thickness), measured chip thickness, and rake all influence the shear angle. Step-by-Step Solution: True feed increases uncut chip thickness → affects chip thickness ratio → alters shear angle.Measured chip thickness is related to shear angle via chip ratio r = t1 / t2 → changes in r shift shear angle.Increasing positive rake tends to increase shear angle, lowering cutting forces. Verification / Alternative check: Experimental plots show shear angle rising with increased positive rake and decreasing with increased friction or higher chip thickness ratios. Why Other Options Are Wrong: Any single factor alone is incomplete; lubrication (E) influences friction and thus shear angle indirectly, but the primary listed parameters (A, B, C) explicitly govern chip geometry and mechanics. Common Pitfalls: Ignoring that feed changes both force and heat via shear angle; assuming shear angle is fixed for a given material. Final Answer: all of these

Production Engineering Questions