Question 1

Single-point tool geometry terminology In metal cutting terminology, the angle measured between the tool face (rake face) and the tool flank (relief face) at the cutting edge is known as what?

Accepted Answer

Introduction / Context: Correct identification of tool angles is fundamental for setting up turning and shaping operations. Each angle serves a distinct purpose: chip flow (rake), avoidance of rubbing (clearance), and edge strength (lip). Misnaming these angles leads to incorrect grinding and poor tool performance. Given Data / Assumptions: Standard single-point cutting tool (e.g., HSS or carbide) for turning. Angles are defined per conventional tool geometry systems. We are considering the local geometry at the primary cutting edge. Concept / Approach: The rake angle is the inclination of the tool face that guides chip flow. The clearance (relief) angle is provided on the flank to prevent rubbing against the machined surface. The lip angle is the included angle between the rake face and the flank at the very cutting edge. It represents edge wedge strength; larger lip angle tends to strengthen the edge but increases cutting forces. Step-by-Step Solution: Identify the two surfaces meeting at the cutting edge: the rake face and the flank.The angle between these two surfaces is defined as the lip angle.Therefore, the term that fits the description is “lip angle.” Verification / Alternative check: Tool grinding charts list lip angle = 90° - rake angle - clearance angle (in a simplified 2D view), reinforcing that it is the included wedge angle at the cutting edge. Why Other Options Are Wrong: Rake angle is between rake face and a reference plane, not the flank. Clearance angle is between flank and machined surface (or a reference plane). Point angle typically refers to the included angle at a drill point or nose angle in lathe tools, not specifically the rake–flank included angle. Inclination angle is a separate 3D feature of tool orientation. Common Pitfalls: Assuming “point angle” is universal for all tools; it is specific to drills or tool nose context. Always check the surfaces defining the angle. Final Answer: Lip angle

Question 2

Effect of shear angle magnitude on chip formation During orthogonal cutting, what happens when the shear angle is small in terms of shear path length and resulting chip thickness?

Accepted Answer

Introduction / Context: The shear angle determines how a material deforms into a chip in orthogonal cutting. It controls chip thickness, cutting forces, and power consumption. Understanding its qualitative effects helps in selecting rake, speed, and lubrication to improve machinability. Given Data / Assumptions: Orthogonal cutting model with a defined rake angle. Steady-state cutting without built-up edge for clarity. Comparing conditions with relatively smaller shear angles. Concept / Approach: Smaller shear angle implies the shear plane is oriented closer to the cutting direction, making the shear plane longer. A longer shear plane increases the area over which plastic deformation occurs, resulting in higher shear work and thicker chips for the same uncut chip thickness. Conversely, a larger shear angle shortens the shear plane and produces thinner chips and lower forces. Step-by-Step Solution: Decrease shear angle ⇒ shear plane tilts, path length increases.Increased shear plane length ⇒ greater deformation zone.Outcome ⇒ chip thickness increases while uncut thickness is unchanged. Verification / Alternative check: Classic cutting analysis shows chip thickness ratio r = t1 / t2 decreases when shear angle decreases, meaning chip thickness t2 grows for a given uncut thickness t1. Why Other Options Are Wrong: Short shear path with thin chip describes a larger shear angle. Short path with thick chip or long path with thin chip are internally inconsistent with the shear plane mechanics. Common Pitfalls: Confusing rake angle with shear angle; while related, it is the shear angle that directly governs chip compression ratio. Final Answer: Long shear path and thick chip

Question 3

Broaching process – key advantages in production Which of the following best summarizes the principal advantages of broaching for internal and external profiles in mass production?

Accepted Answer

Introduction / Context: Broaching uses a multi-tooth tool with progressively increasing tooth heights to remove material in one pass. It is a go-to process for keyways, splines, internal gears, and complex profiles where repeatability and productivity are essential. Given Data / Assumptions: Properly designed broach with roughing, semi-finishing, and finishing teeth in sequence. Workholding provides accurate alignment (e.g., in a vertical or horizontal broaching machine). Suitable material and adequate lubrication are used. Concept / Approach: Because a broach combines many cutting edges, each removing a small increment, the total stock is removed steadily and quickly, achieving high material removal rates with low per-tooth load. The last few teeth are sized to produce the final finish and dimension, delivering excellent accuracy in a single pass. This inherent sequencing enables simultaneous roughing and finishing. Step-by-Step Solution: Identify broach design: progressive teeth for staged stock removal.Productivity: multiple teeth engage simultaneously ⇒ high output.Quality: finishing teeth size the profile for accuracy and finish.Conclusion: all listed advantages apply. Verification / Alternative check: Industrial cycle-time studies consistently show broaching outperforms shaping or slotting for repeated internal profiles, with tight dimensional control. Why Other Options Are Wrong: “Only suitable for soft metals” is false; broaching is used on steels, cast irons, and superalloys with appropriate tool materials and parameters. Common Pitfalls: Ignoring tool re-sharpening intervals; misestimating pull force; inadequate chip evacuation for deep internal broaching. Final Answer: All of the above

Question 4

Drill point angle for mild steel versus brass – statement check Evaluate the statement: “When drilling both mild steel and brass, a 118° point angle is used.” Choose the correct option.

Accepted Answer

Introduction / Context: Drill point angle influences cutting edge strength, chisel edge length, thrust, and entry behavior. Standard general-purpose twist drills for steels commonly use 118°, but optimal angles differ with material to control “grabbing,” edge wear, and chip formation. Given Data / Assumptions: Mild steel is a general-purpose ferrous material. Brass is a free-cutting nonferrous alloy with a tendency to grab if rake is excessive. Tool geometry is the main variable considered. Concept / Approach: For mild steel, 118° is a widely accepted general-purpose point angle. For brass and many copper alloys, practice commonly uses modified geometry: zero or reduced rake (dubbed lips) and point angles often different from 118° to reduce self-feeding and grabbing. Many shops prefer a more blunt point (e.g., around 120°–135°) or special “brass” points; others use 90°–100° for thin sheets. Hence, the universal statement that both materials use exactly 118° is not correct. Step-by-Step Solution: Identify standard for mild steel: ~118° works well.Identify brass behavior: prone to grabbing; geometry is adjusted accordingly.Conclusion: the same fixed 118° for both is inaccurate ⇒ statement is false. Verification / Alternative check: Tool catalogs list dedicated brass drills with altered rake and point geometry distinct from standard 118° HSS drills. Why Other Options Are Wrong: Conditional “true only for …” options are not reliable general rules; brass typically benefits from dedicated geometry. Common Pitfalls: Confusing general-purpose convenience with optimal practice; applying the same point angle to all materials can reduce tool life or hole quality. Final Answer: False

Question 5

Parameter that completely characterizes chip formation kinematics In the orthogonal metal cutting model, which single parameter is used to completely describe the chip formation geometry for a given uncut thickness and rake angle?

Accepted Answer

Introduction / Context: In orthogonal cutting theory, chip formation is modeled as simple shear along a plane characterized by a shear angle. This kinematic description connects uncut chip thickness, chip thickness, and tool rake angle, providing a compact way to discuss chip compression and deformation. Given Data / Assumptions: Orthogonal cutting with constant rake angle and steady-state conditions. Uncut chip thickness and rake are specified. Friction and thermal effects are excluded from the purely geometric description. Concept / Approach: The chip thickness ratio r and shear plane orientation are governed by the shear angle. Once the shear angle is set, the geometric relation among uncut thickness, chip thickness, and rake is fixed. Chip–tool contact length is a frictional/tribological outcome influenced by speed, lubrication, and material; it does not by itself define chip formation kinematics. Step-by-Step Solution: Define geometry: uncut thickness t1, chip thickness t2, rake angle α, shear angle φ.Use geometric relations (e.g., r = t1/t2 as a function of φ and α) to characterize chip compression.Conclusion: shear angle φ completely describes the chip formation geometry for given t1 and α. Verification / Alternative check: Standard derivations relate φ to measurable quantities (like r and α), confirming φ as the single kinematic descriptor of chip formation in the 2D orthogonal model. Why Other Options Are Wrong: Chip–tool contact length is a result, not a defining geometric parameter. Saying both are required mixes cause and effect. Cutting speed influences temperature and friction but does not set the geometric chip relation directly. Common Pitfalls: Conflating geometric descriptors (φ) with process outcomes (contact length, temperature). Ensure model scope is clear. Final Answer: Shear angle

Question 6

Recommended cutting speed for counterboring versus drilling When finishing a previously drilled hole by counterboring (using a multi-lip counterbore), how should the cutting speed compare with that used for the prior drilling operation in the same m…

Accepted Answer

Introduction / Context: Counterboring enlarges the mouth of a hole to a precise diameter and flat-bottom seat for bolt heads or capscrews. Compared with drilling, the tool engagement area is larger and the cutting lips see heavier contact at the same peripheral speed. Given Data / Assumptions: Same work material and similar tool material for drilling and counterboring. Counterbore has multiple cutting edges and a pilot to guide alignment. Goal is dimensional accuracy with good finish. Concept / Approach: Because counterbores engage more material simultaneously at the periphery and must maintain concentricity and surface finish, recommended practice is to use a lower cutting speed than drilling. Lower speed reduces chatter and edge chipping, and helps control heat. Feed is also moderated due to increased lip contact area. Step-by-Step Solution: Compare operations: drilling (point and lips) vs. counterboring (full peripheral lips).Recognize higher load and need for finish in counterboring.Select a reduced cutting speed relative to drilling in the same material. Verification / Alternative check: Machining handbooks list lower surface speeds for counterboring and counter-sinking than for initial drilling to achieve clean, flat seats. Why Other Options Are Wrong: Equal or greater speeds risk chatter and poor finish. “Exactly double” is arbitrary. Independence from material and size ignores standard speed selection practice. Common Pitfalls: Forgetting to use cutting fluid; skipping a pilot can cause bell-mouthing and misalignment. Final Answer: Less than drilling speed

Question 7

Terminology in hole-making operations What is the correct name for the operation that enlarges an existing circular hole using a rotating single-point cutting tool on a lathe or boring machine?

Accepted Answer

Introduction / Context: Multiple processes can produce or refine holes, but each has a specific purpose and tool type. Correct terminology is important for process planning and machine setup. Given Data / Assumptions: An existing hole is present (cast, drilled, or cored). A single-point tool mounted in a boring bar is used. Goal is to enlarge and/or improve location, roundness, and finish. Concept / Approach: Drilling creates a hole with a multi-lip twist drill starting from solid. Reaming uses a multi-edge reamer to bring a drilled/reamed hole to final size with superior finish, removing minimal stock. Counterboring creates a flat-bottom enlargement at the hole entrance for a bolt head. Boring is the only operation among these that enlarges an existing hole using a single-point tool and can correct alignment and geometry. Step-by-Step Solution: Identify tool type: single-point tool in a boring bar.Identify task: enlarge and true an existing hole.Correct term: “boring.” Verification / Alternative check: Lathe operations lists distinguish boring from drilling and reaming by the single-point internal cutting action. Why Other Options Are Wrong: Drilling starts from solid; reaming is finishing at near-size stock; internal turning is a generic phrase and may not imply enlarging a pre-existing hole specifically; counterboring is a localized entrance enlargement. Common Pitfalls: Leaving too little stock for boring after drilling; poor tool overhang causing chatter; neglecting boring bar rigidity. Final Answer: Boring

Question 8

Definition check – template reproduction versus face milling “The operation of reproducing the outline of a template on a workpiece is called face milling.” Evaluate this statement.

Accepted Answer

Introduction / Context: Face milling and template (profile) reproduction are distinct milling operations. Mixing their terminology can lead to confusion in process planning and tool selection. Given Data / Assumptions: Template reproduction involves following a pattern or using a tracer/CNC path to copy a contour. Face milling uses a cutter to generate a flat surface by removing material normal to the cutter axis. We assume conventional manual or CNC milling equipment. Concept / Approach: Face milling is a surface-generation process creating flat faces using a face mill or fly cutter; the dominant motion is perpendicular to the surface. Template reproduction (also called profile milling, copying, or contouring) follows an outline to produce shapes; it relies on edge-following by a tracer stylus or programmed path, not simply surfacing a plane. Step-by-Step Solution: Define face milling: planing of flat surfaces with a face mill.Define template/profile copying: reproducing a contour or shape from a template/NC path.Compare: the statement equates two different operations.Conclusion: the statement is incorrect. Verification / Alternative check: Standard machining texts classify face milling under “surface milling” and template reproduction under “profile/contour milling.” Why Other Options Are Wrong: Conditional “yes” choices still mislabel the process; machine type or material does not change the definition. Common Pitfalls: Using a face mill near edges and assuming it is a profiling tool; correct choice is an end mill or a copying attachment for following contours. Final Answer: No

Question 9

Tapping tool geometry – bottoming tap identification Which feature best characterizes a bottoming tap used to cut threads to the bottom of a blind hole?

Accepted Answer

Introduction / Context: Taps are commonly supplied in three chamfer forms: taper (long chamfer), plug (intermediate chamfer), and bottoming (short chamfer). Correct selection is essential when cutting threads to the full depth in blind holes. Given Data / Assumptions: Standard hand or machine taps are considered. Blind hole requires threads close to the bottom. Material and lubrication are appropriate for tapping. Concept / Approach: A bottoming tap has very little chamfer (typically 1–1.5 threads) so that full-depth threads can be formed almost to the hole bottom. By contrast, a plug tap has about 3–5 threads of chamfer and is used for general tapping, while a taper tap has about 7–10 chamfered threads for easy starting but cannot cut full depth near the bottom. Step-by-Step Solution: Identify the need: fully formed threads near the bottom of a blind hole.Select the tap with minimal chamfer: bottoming tap.Relate to options: “full threads almost to the end (minimal chamfer)” matches bottoming tap geometry. Verification / Alternative check: Tap charts specify chamfer lengths: taper (long), plug (intermediate), bottoming (shortest), confirming the identification. Why Other Options Are Wrong: 3–4 chamfered threads describe plug taps; 8–10 describes taper taps. Spiral flutes and coolant holes are design features independent of the “bottoming” designation. Common Pitfalls: Starting a blind hole with a bottoming tap can be difficult; begin with a taper or plug tap and finish with a bottoming tap to reach full depth. Final Answer: Full threads almost to the end (minimal chamfer)

Question 10

Cutting data for drilling: With a high-speed steel (HSS) twist drill, the typical recommended cutting speed range of 24 to 45 m/min corresponds to drilling which material?

Accepted Answer

Introduction / Context: In machining, selecting the correct cutting speed for a given tool–workpiece combination is essential to balance tool life, productivity, and surface finish. For twist drilling with high-speed steel (HSS) drills, recommended cutting speeds vary substantially with material properties such as hardness, thermal conductivity, and work-hardening behaviour. This item asks which material typically matches the range 24–45 m/min. Given Data / Assumptions: Tool material: HSS twist drill. Target cutting speed window: 24 to 45 m/min. Common workshop materials provided as options: mild steel, copper, aluminium, brass. General shop conditions; no exotic coatings or cryogenic cooling assumed. Concept / Approach: HSS retains hardness only up to moderate temperatures, so speeds are lower than those used with carbides. Copper machines freely and conducts heat well, permitting a mid-range HSS drilling speed higher than mild steel but typically below aluminium or free-cutting brasses. Typical handbook values for HSS drills are roughly: mild steel ~15–30 m/min; copper ~25–45 m/min; aluminium often higher, e.g., 60–90 m/min or more; many brasses also allow higher speeds than copper under similar conditions. Step-by-Step Solution: List typical HSS drilling speed bands by material from common shop practice.Compare the requested band (24–45 m/min) to each material’s usual range.Observe that copper aligns closely with 24–45 m/min.Therefore, select copper as the correct material. Verification / Alternative check: Cross-checking with multiple machining data tables shows mild steel usually falls below the upper 40s with HSS; aluminium and many brasses are often drilled appreciably faster than 45 m/min, validating copper as the best match. Why Other Options Are Wrong: Mild steel: commonly ~15–30 m/min with HSS, below the top of the 24–45 m/min band. Aluminium: typically allows much higher speeds than 45 m/min with HSS. Brass: free-cutting brasses are often drilled faster than copper with HSS. Common Pitfalls: Mistaking spindle speed (r.p.m.) for cutting speed (m/min); ignoring that the same cutting speed corresponds to different r.p.m. depending on drill diameter via v = (π * D * N) / 1000. Final Answer: Copper

Question 11

Grinding fundamentals: A fine-grained grinding wheel is most appropriate for grinding which class of materials?

Accepted Answer

Introduction / Context: The choice of grinding wheel grain size strongly affects chip formation, surface integrity, and wheel wear. Fine grains remove small chips, generate smoother finishes, and distribute cutting forces over more cutting points—characteristics particularly beneficial for certain material classes. Given Data / Assumptions: Wheel variable of interest: grain size (fine versus coarse). Materials to compare: hard/brittle, soft/ductile, hard/ductile, soft/brittle. General surface/cylindrical grinding with conventional abrasives (aluminium oxide or silicon carbide). Concept / Approach: Hard and brittle materials (e.g., hardened tool steels, ceramics, and some carbides) are prone to cracking and subsurface damage if large chips or high forces occur. Fine grain wheels produce smaller chip thickness, reduce individual grit penetration, and help limit micro-cracking. Coarser grains suit soft and ductile materials because larger chip spaces and more aggressive cutting reduce wheel loading and smearing. Step-by-Step Solution: Relate grain size to chip thickness and cutting point density.Identify that fine grains reduce force per grit and chip size.Match to material behaviour: brittle materials need controlled, gentle removal to prevent cracks.Conclude that fine-grained wheels fit hard and brittle materials best. Verification / Alternative check: Surface finish charts and manufacturer recommendations show decreasing grain size for higher hardness and finishing passes, confirming the selection for brittle substrates. Why Other Options Are Wrong: Soft and ductile materials: fine grains tend to clog; coarser, more open structures are preferred. Hard and ductile materials: these typically respond to intermediate choices and tougher bonds rather than the finest grains alone. Soft and brittle materials: uncommon mix; wheel loading is still a risk with fine grains on soft matrices. Common Pitfalls: Confusing grain size with wheel grade (hard/soft bond); grain size governs chip size, whereas grade governs grit retention under load. Final Answer: Hard and brittle materials

Question 12

Turning parameters: Hard and tough materials such as cast iron should generally be turned at what speed regime when using conventional tools?

Accepted Answer

Introduction / Context: Selecting turning speed is a balance between tool life and productivity. Materials that are hard and/or abrasive impose higher cutting forces and temperatures, which accelerate tool wear, especially with high-speed steel (HSS) or uncoated carbide tools. Cast iron, while commonly described as hard and brittle (not tough), is abrasive due to graphite and carbides, demanding conservative speeds. Given Data / Assumptions: Work material: cast iron (abrasive, brittle). Tooling: conventional single-point tools (HSS or basic carbides). Objective: qualitative speed selection. Concept / Approach: Higher speeds increase temperature at the tool–chip interface, worsening flank and crater wear. For abrasive materials, this wear is rapid, so lower speeds (relative to mild steel or aluminium) are recommended. Taylor’s tool life relation V * T^n = C implies that reducing V substantially increases T for a given n, favouring slower speeds for difficult-to-cut materials. Step-by-Step Solution: Assess material abrasiveness and tendency to wear tools.Recognize that cast iron calls for conservative speed to manage wear and temperature.Apply the qualitative implication of Taylor’s relation: reduce speed to extend tool life.Select the “Slow speed” option accordingly. Verification / Alternative check: Typical data show HSS speeds for cast iron below those for mild steel; coated carbides allow increases, but still lower than for aluminium. This confirms the slow-speed choice in general practice. Why Other Options Are Wrong: High speed: exacerbates wear and may burnish or chatter. Any speed: ignores material-specific guidance. Specific single speed: speed depends on tool grade, rigidity, coolant, and depth/feed—no single invariant value exists. Common Pitfalls: Assuming “hard” always means “tough”; cast iron is brittle yet abrasive. Confusing finish-pass speeds with roughing speeds can also mislead selection. Final Answer: Slow speed

Question 13

Lathe kinematics: What is the primary purpose of tumbler gears in a lathe headstock/feed train?

Accepted Answer

Introduction / Context: Tumbler gears are a simple yet critical mechanism in many engine lathes. They determine the direction of rotation transmitted through the change gears or quick-change gearbox to the lead screw or feed shaft, thereby controlling the direction of carriage travel and thread hand (right-hand or left-hand) during threading operations. Given Data / Assumptions: Standard engine lathe with tumbler gear quadrant. Function sought: what tumbler gears primarily accomplish. Focus on feed direction rather than speed selection. Concept / Approach: By swinging the tumbler gear arm to mesh alternative idler paths, the number of gear inversions is changed. An odd number of gear meshes reverses the rotation direction delivered to the lead screw/feed shaft; an even number maintains it. This allows quick reversal of carriage feed and selection of thread hand without reversing the main spindle motor. Step-by-Step Solution: Identify that tumbler gears alter gear inversion count in the feed train.Recognize the effect: reversing or maintaining the feed direction.Connect to carriage motion and thread hand selection.Select the option describing feed direction control. Verification / Alternative check: Operating a lathe shows the tumbler lever switches between forward, neutral, and reverse feed positions, confirming the function. Why Other Options Are Wrong: Reduce spindle speed: governed by belt/gear ratios or gearbox, not tumbler alone. Cut gears: gear cutting requires specific setups and indexing, not just tumbler gears. Drilling: performed with tailstock or turret, unrelated to tumbler gear function. Common Pitfalls: Confusing change gears (ratio selection) with tumbler gears (direction selection). They are related but distinct mechanisms. Final Answer: Provide the desired direction of movement to the carriage (feed reversal/selection)

Question 14

Taylor tool-life exponents: In the relation V * T^n = C, the usual range of exponent n for high-speed steel (HSS) tools is stated as 0.25 to 0.40. Is this statement correct?

Accepted Answer

Introduction / Context: Taylor’s tool life equation, V * T^n = C, is a fundamental empirical relation in machining. The exponent n depends strongly on the tool–work combination. Knowing realistic ranges for n helps in estimating how speed changes will affect tool life. Given Data / Assumptions: Tool material under consideration: HSS. Proposed range for n: 0.25 to 0.40. General steel machining under normal conditions. Concept / Approach: For HSS, n is typically small because HSS is sensitive to temperature; modest increases in speed drastically reduce tool life. Commonly cited ranges are around n ≈ 0.08 to 0.20 for HSS depending on work material and environment. Higher exponents in the 0.25 to 0.40 range are more characteristic of carbides and some ceramics or coated tools where hot hardness is superior. Step-by-Step Solution: Recall typical n ranges by tool class: HSS (low n), carbides/ceramics (higher n).Compare the stated 0.25–0.40 with HSS norms (≈0.08–0.20).Conclude the statement does not match standard data for HSS.Therefore, choose “Disagree”. Verification / Alternative check: Shop references and textbooks list example values: HSS often n ≈ 0.1; uncoated carbide n ≈ 0.2–0.25; coated or cermet tools can be higher, corroborating the reasoning. Why Other Options Are Wrong: Agreeing would misattribute carbide-like behavior to HSS, overestimating HSS tolerance to speed increases. Common Pitfalls: Using a single n value universally; n varies with coolant use, work material, and wear criterion (e.g., flank wear land). Always treat ranges as indicative, not absolute. Final Answer: Disagree

Question 15

Tool geometry choice: Negative rake angles are typically employed for which situations or tools?

Accepted Answer

Introduction / Context: Rake angle selection influences cutting action, edge strength, and heat distribution. Negative rake strengthens the cutting edge and shifts the shear plane, often used with tougher tool materials or demanding cuts. Given Data / Assumptions: Considering standard single-point or indexable inserts. Comparing use cases: carbide tools, heavy loads, hard materials. Conventional machine rigidity and proper fixturing assumed. Concept / Approach: Negative rake increases wedge angle, providing a stronger edge that resists chipping under impact and high compressive loads. Carbide has high hot hardness but is brittle; using negative rake protects the edge in interrupted cuts and during heavy feeds and depths. When machining harder materials, negative rake helps withstand higher forces and temperatures, albeit at the expense of higher cutting power and more heat into the work. Step-by-Step Solution: Relate negative rake to edge strength and load capacity.Match to tool material: carbides benefit from stronger wedge angles.Match to operation: heavy cuts and hard materials demand robust edges.Therefore select “All of these”. Verification / Alternative check: Insert catalogs list many negative-rake geometries (e.g., square SN** series) for roughing steel and cast iron at heavy feeds; positive-rake inserts are preferred for low power machines or soft, gummy metals. Why Other Options Are Wrong: Choosing any single case ignores the broad applicability of negative rake across all three scenarios listed. Common Pitfalls: Assuming negative rake is always better; for light machines or ductile gummy materials (e.g., aluminium), positive rake reduces forces and improves chip evacuation. Final Answer: All of these

Question 16

Oblique versus orthogonal cutting: In the oblique cutting system, how does the cutting edge relate to the workpiece width?

Accepted Answer

Introduction / Context: Chip formation analysis distinguishes orthogonal cutting (cutting edge perpendicular to cutting velocity direction) from oblique cutting (edge inclined). This geometric difference changes chip flow, force components, and the relationship between the cutting edge and workpiece width. Given Data / Assumptions: Oblique cutting: cutting edge is at an inclination angle to the direction of tool travel. Orthogonal cutting: cutting edge spans and is perpendicular to the direction, clearing the full width. Typical turning or milling with inclined edge. Concept / Approach: In orthogonal cutting, the straight edge normally spans the entire width of cut. In oblique cutting, the cutting edge is set at an angle; the instantaneous contact may or may not cover the whole width, and chip flows sideways along the rake face. Therefore, it is not a requirement of oblique cutting that the edge always clears the full width. Step-by-Step Solution: Recall definitions: orthogonal versus oblique cutting edge orientation.Note that oblique cutting can involve partial or full engagement across width depending on setup.Conclude: “may or may not clear the full width.”Choose the corresponding option. Verification / Alternative check: Textbook diagrams depict oblique cutting with a chip flow angle different from zero, demonstrating that contact distribution along the edge varies and full-width clearance is not guaranteed. Why Other Options Are Wrong: Options stating “must” or “may not” exclusively are too restrictive for oblique cutting; the geometry allows both possibilities depending on edge length, approach angle, and width of cut. Common Pitfalls: Assuming orthogonal cutting conditions apply to all cutting cases; many practical tools use oblique geometry to improve chip flow and surface finish. Final Answer: It may or may not clear the full width of the workpiece

Question 17

Tool wear mechanisms: Flank wear mainly results from abrasive action of hard micro-constituents and debris (including from built-up edge) rubbing along the machined surface. Is this statement correct?

Accepted Answer

Introduction / Context: Flank wear is a dominant wear mode for single-point tools during continuous cutting. Understanding its causes helps in selecting tool materials, cutting parameters, and coolants, thereby prolonging tool life and improving dimensional accuracy. Given Data / Assumptions: Standard turning with a defined flank face rubbing the just-machined surface. Presence of hard inclusions or micro-constituents in the work (e.g., carbides, oxides), and possible built-up edge (BUE) debris. Normal cutting speeds and feeds without extreme thermal shock. Concept / Approach: Flank wear occurs on the clearance (flank) face that is in proximity to the finished surface. The primary mechanism is abrasive scratching and micro-ploughing by hard particles in the work material or detached BUE fragments sliding along the tool flank. Adhesion and diffusion can contribute, but abrasion is predominant for many steels and cast irons. As flank wear land grows, cutting forces and temperatures rise, accelerating further wear. Step-by-Step Explanation: Hard micro-constituents in the workpiece contact the flank during sliding.These particles abrade the tool flank, forming a measurable wear land (VB).BUE forms intermittently on the rake face; fragments detach and can act as additional abrasive debris.Elevated temperature promotes softening and oxidation, which can further assist abrasion and adhesion, closing the wear loop. Verification / Alternative check: Metallographic inspection of worn tools typically shows scoring lines on the flank corresponding to abrasive trajectories; wear rate correlates with work hardness and inclusions. Why Other Options Are Wrong: Marking the statement “Incorrect” ignores well-documented abrasive mechanisms on the flank; other mechanisms (diffusion, oxidation) exist but are not the principal cause in many common operations. Common Pitfalls: Confusing crater wear (on rake face due to chip flow and diffusion) with flank wear; assuming coolant eliminates abrasion—coolant reduces but does not remove abrasive contact. Final Answer: Correct

Question 18

Gear manufacturing – hobbing: During gear hobbing, which components rotate during the generating process?

Accepted Answer

Introduction / Context: Hobbing is a versatile generating process for cutting spur, helical, and worm gears. Understanding the kinematics is vital for setting up the correct module, number of teeth, and helix angle on a hobbing machine. Given Data / Assumptions: Standard gear hobbing machine and worm-type hob. Goal: identify which elements rotate during cutting. Generating method (not form milling) is assumed. Concept / Approach: In generating processes, the final tooth form results from the relative rolling motion between tool and workpiece, not from a stationary form template. In hobbing, the hob rotates continuously while the gear blank also rotates; their angular velocities are linked by a precise gear ratio proportional to the number of teeth and module. Feed motions (axial or radial) advance the hob through the blank to complete the tooth spaces. Step-by-Step Solution: Recognize hobbing as a generating process requiring relative rotation.Recall that the hob acts like a worm; the blank must roll with it.Therefore, both the hob and blank rotate with synchronized speeds.Select the option that states both rotate. Verification / Alternative check: Machine kinematic diagrams show a change-gear train or electronic synchronization (in CNC hobbers) coupling hob and worktable rotation. Why Other Options Are Wrong: “Only one rotates” would be a shaping or fly-cutting scenario; “neither rotates” cannot generate involute teeth. Common Pitfalls: Confusing gear form milling (form tool, no generating roll) with hobbing; mis-setting the ratio causes the wrong tooth count. Final Answer: Both hob and gear blank rotate (timed to a gear ratio)

Question 19

Tool identification: The numerical method of specifying a single-point tool by listing its key angles and features is called the tool signature. Is this statement correct?

Accepted Answer

Introduction / Context: Single-point cutting tools are defined by a set of geometric parameters (rake angles, clearance angles, nose radius, etc.). A compact way to communicate these values for manufacturing, inspection, and setup is the tool signature system. Given Data / Assumptions: Use of ASA, ORS/ISO, or NRS systems to denote angular values and nose radius. Angles are typically recorded in degrees; nose radius in mm. Applies to turning tools and other single-point geometries. Concept / Approach: A tool signature is a sequence of numbers, each representing a specific element of tool geometry in an agreed order. For example, in one common convention: Back rake – Side rake – End relief – Side relief – End cutting edge angle – Side cutting edge angle – Nose radius. Listing these in numerals allows unambiguous identification and replication of a tool's cutting geometry. Step-by-Step Explanation: Identify the relevant geometry set (rakes, clearances, edge angles, nose radius).Assign each value to its position within the signature sequence as per the chosen standard.Express the set numerically to fully specify the tool.Use this signature across design, grinding, and setup instructions. Verification / Alternative check: Textbook examples show signatures like 8-6-5-5-10-15-0.8 mm, which can be interpreted directly into the corresponding tool angles and nose radius. Why Other Options Are Wrong: Labeling the statement “Incorrect” would ignore established nomenclature used universally in toolrooms and machining handbooks. Common Pitfalls: Mixing different systems (ASA vs ORS) without noting the order; omitting the nose radius value, leading to incomplete specification. Final Answer: Correct

Question 20

Lathe workholding: Which chuck is preferred for quick setup and accurate self-centering of a job? (Consider general turning of regular round workpieces in a conventional engine lathe.)

Accepted Answer

Introduction / Context: Workholding is fundamental to machining accuracy and productivity. In lathe operations, the choice of chuck affects how quickly a part can be set up and how accurately it is centered on the spindle axis. This question focuses on the most widely used chuck for rapid setup with reliable self-centering. Given Data / Assumptions: Regular, mostly cylindrical bar stock or round workpieces. General-purpose engine lathe in a job shop or training environment. Need for quick setup and good concentricity without extensive dial-indicating. Concept / Approach: The three-jaw universal chuck uses a scroll mechanism to move all jaws simultaneously. This self-centering action quickly brings round or hex work to the spindle axis with typical runout suitable for most turning tasks. It trades ultimate concentricity for speed and convenience but is the default for everyday work. Step-by-Step Solution: Identify self-centering need → requires linked jaw motion (scroll chuck).Identify “quick setting” need → simultaneous jaw movement saves time.Select the device that provides both → three-jaw universal chuck. Verification / Alternative check: Shop practice: for round bar, a three-jaw universal chuck is typically the first choice; four-jaw independent is used when off-center turning or the highest possible concentricity via indicating is needed. Why Other Options Are Wrong: Four-jaw independent: highest versatility and accuracy after indicating, but not “quick” to set for most parts.Collet chuck: very accurate and fast for specific diameters, but requires matching collets and is best for small, precise production runs, not general quick changeover.Magnetic chuck/Faceplate: suited to special shapes or flat work; not a standard rapid self-centering solution for round stock. Common Pitfalls: Assuming “most accurate” always equals “fastest.” Four-jaw and collets can be more accurate in specific contexts, but for general quick centering the three-jaw universal is preferred. Final Answer: Three-jaw universal (self-centering) chuck

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