Manufacturing Exam#2

Flat Rolling

• How to Identify: A strip, sheet, or plate passing between two opposing horizontal, cylindrical rotating rolls; workpiece thickness decreases from $h_0$ to $h_f$ while length increases.

• When to Use: High-volume production of continuous metal stock with uniform rectangular cross-sections (plates $> 0.25\text{ in.}$, sheets $< 0.25\text{ in.}$, foil).

• Why to Use: Highest throughput and lowest per-unit cost for continuous raw stock; cold flat rolling yields exceptional surface finish, tight tolerances, and strain-hardening strength.

Roll Deflection & Crown / Camber

• How to Identify: Rolls bending elastically under massive roll forces like a simply supported beam; causes a strip with a thick center and thin edges, or wavy edges if over-corrected. Corrected rolls have a barrel-shaped crown (convex center).

• When to Use: Cambered rolls are ground thicker in the middle specifically for heavy-draft rolling operations.

• Why to Use: Under full rolling load, the roll flexes flat, ensuring uniform sheet thickness across its entire width and preventing edge-waviness or center-zipper defects.

Four-High Mill & Sendzimir (Cluster) Mill

• How to Identify:

  • Four-High: Two small-diameter work rolls directly in contact with the strip, backed by two massive backup rolls.

  • Sendzimir: Two tiny work rolls nested inside an array of multiple intermediate and backup rolls.

• When to Use: Cold-rolling thin, high-strength alloy sheets, stainless steel, and foils.

• Why to Use: Smaller work-roll radius ($R$) drastically reduces contact length ($L = \sqrt{R \Delta h}$), cutting total roll force and power; large backup rolls prevent work rolls from deflecting.

Shape Rolling

• How to Identify: Billet passes through a sequence of grooved rolls that gradually impart a contoured, non-flat cross-section.

• When to Use: Structural beams (I-beams, H-beams, T-sections, channels), railroad tracks, and vehicle chassis rails.

• Why to Use: Eliminates joining/welding multiple plates together, producing continuous, high-strength structural profiles without severed grain lines.

Ring Rolling

• How to Identify: A thick-walled, donut-shaped ring blank placed between a driven roll and an idle pressure roll; the wall thickness decreases while the ring diameter expands.

• When to Use: Large seamless rings, jet engine turbine rings, rocket motor casings, pipeline flanges, roller bearing races, and turret rings.

• Why to Use: Yields continuous circumferential grain flow, eliminating the weak weld seams and thermal distortions of fabricated rings.

Roll Forging

• How to Identify: Opposing cylindrical rolls containing shaped die impressions along part of their circumference; the bar is fed in and squeezed as the rolls rotate.

• When to Use: Tapered shafts, leaf springs, knife blades, connecting rod preforms, dumbbells, and hand tools.

• Why to Use: Rapidly creates lengthwise cross-sectional variations with continuous grain flow, serving as an efficient preforming step for impression-die forging.

Skew Rolling

• How to Identify: Two counter-rotating rolls with spiral helical grooves set at an angle (skewed) to each other, feeding a round bar continuously through the gap.

• When to Use: High-speed, continuous manufacturing of spherical ball bearings and short cylindrical slugs.

• Why to Use: Massive production rates (hundreds of balls per minute) directly from bar stock without flash or material scrap.

Rotary Tube Piercing (Mannesmann Process)

• How to Identify: Two skewed rolls rotating in the same direction pull a heated round billet over a stationary internal mandrel/plug; tensile hoop stresses tear an internal cavity at the center.

• When to Use: Manufacturing heavy-wall, seamless steel tubing and pressure pipe.

• Why to Use: Creates thick-walled, high-pressure tubing with no longitudinal weld seam, avoiding pressure-burst vulnerabilities.

Open-Die Forging (Cogging & Upsetting)

• How to Identify: Workpiece placed between simple flat or shallow open dies; material is unconstrained laterally and barrels at the free edges due to die friction.

• When to Use: Extremely large, heavy components (ship propeller shafts, large rings, turbine rotors) and low-volume preforming.

• Why to Use: Tooling costs are minimal; refines cast ingot structure and consolidates internal porosity into dense wrought grain structures.

Impression-Die Forging

• How to Identify: Workpiece is compressed between two contoured die halves; excess metal squirts laterally through a narrow flash gap into a gutter.

• When to Use: Automotive connecting rods, crankshafts, steering knuckles, aerospace landing gear, and high-strength wrench handles.

• Why to Use: Flash cools rapidly and acts as a choke, building immense hydrostatic cavity pressure that forces metal into intricate, tight die features while aligning continuous grain flow along the part contours.

Closed-Die (Flashless / Precision) Forging

• How to Identify: Dies enclose the workpiece entirely without a flash gap; zero flash forms around the parting line.

• When to Use: High-precision gears, valve bodies, and aerospace turbine discs made of costly alloys (titanium, nickel superalloys).

• Why to Use: Near-net shape with zero material scrap and minimal post-machining; requires precise billet volume control to prevent die over-pressurization.

Heading (Cold Upsetting)

• How to Identify: Round wire or rod stock is fed against a stop, sheared to length, and stamped on the end by a punch inside a gripping die to form an enlarged head.

• When to Use: Mass production of fasteners (screws, bolts, nails, rivets) and spark plug bodies.

• Why to Use: Cycle rates of several hundred fasteners per minute with zero chip waste, plus work-hardened heads that resist stripping.

Rotary Swaging

• How to Identify: Multiple radial dies reciprocate rapidly (hammering inward hundreds of times per minute) driven by roll bearings in a cage while rotating around the workpiece.

• When to Use: Tapering solid bars, reducing outer diameters of tubes, swaging cables onto fittings, and forming internal rifling in gun barrels (over an internal mandrel).

• Why to Use: Rapid, flashless net-shape forming of axisymmetric tapers and steps with exceptional dimensional accuracy and surface finish.

Coining

• How to Identify: Completely closed-die pressing with flat or engraved dies under massive compressive pressures; no flash allows fine surface reliefs to be imprinted.

• When to Use: Coins, medals, decorative medallions, and precision sizing of sintered powder metallurgy parts.

• Why to Use: Extreme surface detail reproduction and ultra-tight thickness repeatability.

Direct (Forward) Extrusion

• How to Identify: Ram pushes a heated billet forward inside a stationary container; metal exits the die in the same direction as ram movement.

• When to Use: Architectural aluminum window frames, solid round bars, tubing, and symmetric structural channels.

• Why to Use: Simpler press architecture and easier handling of long extruded profiles, though billet-container friction causes a steep initial force peak.

Indirect (Backward / Reverse) Extrusion

• How to Identify: Die is mounted on a hollow stem that moves into a closed stationary container; metal flows in the opposite direction of ram motion.

• When to Use: Hard-to-extrude, high-strength alloys and shorter parts.

• Why to Use: Eliminates relative motion between billet and container wall, reducing extrusion force by $20\text{--}30\%$, saving energy, and generating a uniform temperature and strain profile.

Hydrostatic Extrusion

• How to Identify: Billet is surrounded by high-pressure hydraulic fluid inside the container; the ram pressurizes fluid rather than contacting the billet directly.

• When to Use: Brittle metals (molybdenum, tungsten, cast iron) and clad/composite conductors.

• Why to Use: Zero container-wall friction, and high triaxial compressive stress increases material ductility, preventing cracking.

Impact Extrusion

• How to Identify: A high-velocity punch strikes a lubricated metal slug in a shallow die cavity; metal squirts backwards up around the punch or forward through a die orifice.

• When to Use: Toothpaste tubes, aerosol cans, flashlight bodies, battery casings, and beverage can preforms.

• Why to Use: Extremely fast cycle times (up to $2\text{--}3\text{ parts/sec}$), thin walls, and hollow cup shapes produced in a single stroke.

Hollow Extrusion with Spider / Bridge Dies

• How to Identify: Internal mandrels supported by bridges ("spiders") inside the die; metal splits around the bridges and pressure-welds back together in a welding chamber before exiting.

• When to Use: Multi-void aluminum extrusions, automotive bumper beams, and hollow heat-sink channels.

• Why to Use: Produces complex hollows and multi-chamber tubes without requiring secondary welding or long internal mandrel bars.

Rod, Wire, and Tube Drawing

• How to Identify: The cross-section is reduced by pulling (tensile pulling force at exit) through a tapered convergence die rather than pushing.

• When to Use: Electrical copper wiring, guitar strings, precision musical instrument tubing, and needle tubes.

• Why to Use: Generates exact cross-sectional diameters, bright drawn surface finishes, and work-hardened tensile strength.

Shearing (Punching vs. Blanking)

• How to Identify: Cut edge shows rollover, a smooth burnished band, a rough fracture zone, and an exit burr.

  • Punching: Cut-out piece is scrap; the remaining sheet with the hole is the part.

  • Blanking: Cut-out piece is the desired part; remaining skeleton is scrap.

• When to Use: First step in nearly all sheet-metal workflows to produce flat profile shapes or mounting holes.

• Why to Use: High-speed, low-cost separation of flat stock; die-punch clearance must be maintained (2-8%t) to ensure clean shear without ragged edges or excessive burrs.

Springback in Bending

• How to Identify: The bend angle decreases and the bend radius increases after the punch is unloaded ($R_f > R_i$).

• When to Use: Evaluated on every sheet bending operation (press brake, V-die, wipe die).

• Why to Use: Must be compensated for via overbending, bottoming/coining, or stretch bending; springback ratio $R_i / R_f$ is proportional to $R_i Y / (E t)$.

Stretch Forming

• How to Identify: Sheet metal blank is gripped at opposite edges by mechanical jaws, pulled in tension beyond its yield point, and draped/stretched over a male form die.

• When to Use: Large, gently curved aerospace panels (aircraft fuselage and wing skins) and ultra-thin smartphone speaker diaphragms.

• Why to Use: Eliminates springback entirely (because through-thickness stress is uniformly tensile) and requires only a single male die rather than an expensive matching die set.

Deep Drawing

• How to Identify: A flat circular blank held down by a blankholder ring is pushed into a round die cavity by a punch, converting flat sheet into a seamless cylindrical cup.

• When to Use: Beverage cans, kitchen sinks, cooking pots, automotive gas tanks, and oil filter housings.

• Why to Use: High-speed forming of hollow, seamless vessels without welding; drawability depends on normal plastic anisotropy ($R$-value).

Hydroforming & Tube Hydroforming

• How to Identify:

  • Sheet Hydroforming: Pressurized hydraulic fluid backed by a rubber diaphragm acts as the female die.

  • Tube Hydroforming: Tubular blank placed in split dies is expanded by high-pressure internal water while axial punches feed tube ends inward.

• When to Use: Automotive exhaust manifolds, unibody engine cradles, frame rails, and bicycle frames.

• Why to Use: Replaces assemblies made of multiple stamped and welded brackets with a single seamless component; eliminates welds, reduces weight by $20\text{--}30\%$, and provides uniform wall thickness.

Conventional & Shear Spinning

• How to Identify: A flat circular blank clamped against a rotating form mandrel on a lathe is shaped progressively by a smooth roller tool.

• When to Use: Rocket nose cones, satellite dish reflectors, cooking woks, brass musical instrument bells, and large aluminum lighting shades.

• Why to Use: Extremely low tooling costs for large axisymmetric hollow shapes; ideal for low-to-medium batch sizes where deep drawing dies would be cost-prohibitive.

Orthogonal vs. Oblique Cutting

• How to Identify:

  • Orthogonal: Two-dimensional cutting model where the straight cutting edge is perpendicular ($90^\circ$) to the cutting velocity vector.

  • Oblique: Three-dimensional cutting where the cutting edge is inclined at an acute angle; chips coil sideways.

• When to Use: Orthogonal is used in experimental tests and theoretical derivations; oblique represents real-world turning, milling, and drilling.

• Why to Use: Orthogonal simplifies complex 3D chip mechanics down to two shear forces and measurable planar angles for calculation.

Positive vs. Negative Rake Angles (α)

• How to Identify:

• Positive Rake: Tool face slopes away from the cut direction (like a sharp slicing knife).

• Negative Rake: Tool face tilts forward against the cutting direction (blunt, wedge-like).

• When to Use:

• Positive: Low-strength ductile materials, delicate/slender workpieces, low-power machines.

• Negative: Heavy-duty roughing, interrupted cuts, machining hardened tool steels, and brittle inserts (ceramic, carbide).

• Why to Use: Positive lowers cutting forces, power, and temperatures; negative directs cutting forces into compression, protecting brittle insert tool tips from chipping and catastrophic fracture.

Chip Types (Continuous, BUE, Discontinuous, Serrated)

• How to Identify:

• Continuous: Long, smooth ribbon chips. (Ductile metals, high speed, positive rake).

• Built-Up Edge (BUE): Workpiece metal strain-hardens and welds onto tool tip; flaking off leaves a poor, rough finish. (Low/medium speeds, ductile metals).

• Discontinuous: Fractured, segmented chip blocks. (Brittle materials like cast iron, high friction, low speeds).

• Serrated / Shear-Localized: Saw-toothed chip profile. (Difficult-to-machine metals like titanium alloys at high cutting speeds).

• When to Use / Observe: Evaluated continuously during machining parameter setup.

• Why to Use: Continuous chips with chip breakers yield the best surface finish and tool longevity; BUE must be eliminated by increasing cutting speed or using effective cutting fluid.

Climb (Down) vs. Conventional (Up) Milling

• How to Identify:

• Climb (Down): Cutter tooth moves in the same direction as table feed; chip thickness starts at maximum and tapers to zero at exit.

• Conventional (Up): Cutter tooth moves against feed; chip thickness starts at zero and increases to maximum.

• When to Use:

• Climb: Modern CNC mills with backlash eliminators (standard preferred choice).

• Conventional: Castings/forgings with abrasive hard surface scale, or older manual knee mills with table backlash.

• Why to Use: Climb milling yields superior surface finish, lowers cutter wear, and pushes workpiece down into the fixture rather than lifting it up.

Drilling vs. Boring vs. Reaming vs. Trepanning

• How to Identify:

  • Drilling: A multi-flute rotating twist drill creates a round hole directly from solid stock.

  • Boring: Single-point tool enlarges an existing hole to precise concentricity and diameter.

  • Reaming: Fluted multi-edge tool removes a minute layer (0.005- 0.015 in) from a pre-drilled hole.

  • Trepanning: Annular rotary cutter removes a cylindrical core rather than turning all internal material into chips.

• When to Use:

  • Drilling = initial rough opening.

  • Boring = correcting hole axis straightness/concentricity.

  • Reaming = final tight tolerance and mirror surface finish.

  • Trepanning = large diameter holes (> 2 in.) in heavy plate/bar.

• Why to Use: Separates rough bulk material removal from high-precision finishing, preventing tool deflection from compromising final dimensions.

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Hot Hardness & Cutting Tool Material Hierarchy

• Identification: The ability of a tool material to retain its hardness, shape, and yield strength at high temperatures without undergoing plastic deformation1. Ranked in order of increasing hot hardness and allowable cutting speed: Carbon Tool Steels → High-Speed Steels (HSS)→Cast Cobalt Alloys→ Carbides / Coated Carbides → Ceramics → Polycrystalline Cubic Boron Nitride (cBN) →Diamond

• When to Use:

  • HSS: Low-to-moderate cutting speeds, high-shock interrupted cuts, complex-geometry tools (drills, form taps, broaches)

  • Carbides & Ceramics: High-speed, high-volume production turning and milling of cast irons and hard steels

  • Diamond / PCD: Non-ferrous alloys, aluminum, brass, abrasive composites, and graphite

• Why: High cutting speeds generate extreme shear zone and friction temperatures (often exceeding 700 C to 1000 C). Without adequate hot hardness, cutting edges soften, undergo plastic blunting, lose dimensional accuracy, and fail prematurely

Coated Carbide Inserts

• Identification: Indexable carbide inserts covered with micro-thin layers of TiN (gold-colored), TiC, TiCN, or Al2O3.

• When to Use: General-purpose high-speed turning, milling, and heavy roughing of steels and cast irons.

• Why: Outer hard coatings act as a chemical diffusion barrier and lower friction, resisting crater and flank wear, while the tough carbide substrate absorbs cutting shocks.

Polycrystalline Diamond (PCD) Tools

• Identification: Ultra-hard diamond cutting tip sintered onto a carbide substrate or shank.

• When to Use: Precision finishing of high-silicon aluminum, brass, copper, carbon-fiber composites, and ceramics.

• Why / Limitation: Produces mirror surface finishes with near-zero edge wear. Cannot be used on steels, stainless steels, or cast iron because iron chemically reacts with diamond at high temperatures, dissolving the carbon into the steel.

Cubic Boron Nitride (cBN / PCBN)

• Identification: Second-hardest known material after diamond, sintered onto a carbide base.

• When to Use: High-speed finishing and hard turning of hardened steels (45–65 HRC), chilled cast irons, and nickel superalloys.

• Why: Chemically inert to ferrous metals even past 1000°C, providing extreme hot hardness and wear resistance without the chemical breakdown that diamond suffers on steel.

Tool Wear Modes (Flank, Crater, Nose, Notching)

• Identification:

• Flank Wear: Abrasive rubbing flat on the relief/flank face.

• Crater Wear: Concave scooped depression on the rake face caused by diffusion and heat.

• Nose Wear: Rounding of the tool tip radius.

• Notching: Localized groove at the depth-of-cut line from work-hardened scale.

• When to Use / Observe: Evaluated during tool life monitoring; governed by the Taylor Tool Life Equation (V * T^n = C), where cutting speed has the greatest impact on tool life.

• Why: Flank wear governs dimensional tolerances and surface finish; crater wear weakens the cutting edge until premature chipping or fracture occurs.

Cutting Fluids (Straight Oils, Soluble Oils, Synthetics)

• Identification: Clear straight oils, milky oil-in-water emulsions (soluble oils), or chemical synthetic fluids applied by flooding, misting, or high-pressure through-spindle jets.

• When to Use: Heavy turning, hole tapping, deep drilling, and ductile metal machining.

• Why / Precaution: Cools the shear zone, lubricates chip sliding, lowers cutting power, and flushes chips away. In interrupted cuts (like milling with carbide or ceramic inserts), intermittent fluid causes thermal shock and cracking, making dry machining preferable.

Straight Turning

• Identification: Cylindrical workpiece rotates in the lathe spindle while a single-point tool feeds parallel to the rotational axis.

• When to Use: Uniform reduction of outside diameter (OD) on cylindrical shafts, pins, and bars.

• Why: Fundamental operation for axisymmetric components; broken into heavy-feed roughing passes followed by high-speed, light-feed finishing passes.

Facing

• Identification: Single-point tool feeds radially perpendicular to the spindle axis across the end face of a rotating workpiece.

• When to Use: Squaring the ends of parts, creating reference datums, and trimming parts to exact overall length.

• Why: Removes rough saw-cut surfaces and scale, guaranteeing perpendicularity with the spindle centerline.

Taper Turning

• Identification: Generating a conical profile where diameter changes linearly along the length.

• When to Use: Machine tool tapers (Morse tapers), conical pins, and valve seats.

• Why: Produced via swiveling the compound rest, using a taper attachment, offsetting the tailstock, or programming 2-axis CNC toolpaths.

Parting-Off and Grooving

• Identification: Narrow rectangular blade tool plunges radially inward toward the centerline.

• When to Use: Cutting snap-ring/O-ring grooves, or severing finished components from bar stock.

• Why: Cleanly cuts parts to length directly on the machine without needing a secondary bandsaw operation.

Boring & Boring Bars

• Identification: Single-point tool mounted on a rigid horizontal bar feeding axially inside an existing hole.

• When to Use: Internal hollow cylinders, large engine cylinder bores, and bearing seats.

• Why: Unlike twist drills (which can wander or drift), boring straightens misaligned or out-of-round holes to exact diameter, roundness, and finish.

Right-Hand vs. Left-Hand Turning Tools

• Identification:

• Right-Hand Tool: Cuts while moving from right to left (toward the chuck/headstock).

• Left-Hand Tool: Cuts while moving from left to right (toward the tailstock).

• When to Use: Right-hand tools for standard OD turning against the rigid spindle; left-hand tools for turning toward the tailstock or facing specific shoulders.

• Why: Correct tool orientation directs cutting forces into the toolholder seat pocket, maximizing rigidity and preventing chatter.

Twist Drilling vs. Gun Drilling vs. Trepanning

• Identification:

• Twist Drill: Two helical flutes and a chisel edge creating holes from solid stock.

• Gun Drill: Single straight flute with an internal high-pressure coolant hole and guide pads.

• Trepanning: Annular rotating cutter that cuts an outer ring groove to leave a solid central core.

• When to Use: Twist drilling for standard holes (L/D up to ~5:1); gun drilling for deep precision holes (L/D up to 50:1); trepanning for large-diameter holes (> 2 in.) in plates/bars.

• Why: Gun drills flush chips out continuously and prevent bit wander; trepanning removes large holes rapidly without wasting power turning the entire center into chips.

Reaming & Tapping

• Identification:

• Reaming: Fluted rotary finishing tool removing 0.005–0.015 in. of material from an existing hole.

• Tapping: Multi-fluted screw cutter that cuts internal threads.

• When to Use: Precision hole sizing (e.g., dowel pin holes) and creating internal screw threads for bolts.

• Why: Reaming guarantees tight diametrical tolerances and mirror surface finish; tapping enables standardized threaded fastener assembly.

Peripheral (Slab) Milling

• Identification: Cutter rotational axis is parallel to the workpiece surface; teeth on the cylindrical periphery cut the material.

• When to Use: Wide, flat horizontal plates, long structural slots, splines, and gear teeth.

• Why: Capable of taking heavy-width cuts over long surfaces using sturdy horizontal milling arbors.

Face Milling

• Identification: Cutter rotational axis is perpendicular to the machined surface; teeth cut on both the flat face and peripheral corner.

• When to Use: Large flat surfaces on engine blocks, machine beds, and gearbox covers.

• Why: High metal removal rates and exceptional surface flatness; broad cutter bodies cover wide areas in a single pass.

End Milling

• Identification: Shank-mounted cutter with cutting edges on both its cylindrical sides and its bottom end face.

• When to Use: Pockets, slots, stepped shoulders, keyways, and complex 2D/3D profile perimeters.

• Why: High versatility; can plunge vertically into material and traverse sideways to pocket out complex shapes.

End Mill Styles (Flat, Ball-Nose, Bull-Nose, Roughing)

• Identification:

• Flat: Sharp 90° corners and flat bottom.

• Ball-Nose: Hemispherical rounded nose.

• Bull-Nose: Flat bottom with rounded corner radii.

• Roughing: Wavy, scalloped serrations along the flutes.

• When to Use: Flat for square pockets and shoulders; Ball-nose for 3D contoured dies, molds, and turbine blades; Bull-nose for tough pocketing in steel/titanium; Roughing for heavy bulk material removal.

• Why: Ball-nose creates smooth organic contours; bull-nose prevents corner chipping; roughing breaks chips into small segments, lowering cutting forces and chatter.

Climb (Down) vs. Conventional (Up) Milling

• Identification:

  • Climb: Cutter moves in the same direction as table feed; chip starts thick and tapers to zero at exit.

  • Conventional: Cutter opposes feed; chip starts at zero and widens to maximum at exit.

• When to Use: Climb on modern CNC machines with backlash eliminators; Conventional on older manual mills with leadscrew backlash or parts with hard surface scale.

• Why: Climb milling pushes the workpiece down into the fixture, extends tool life, and provides superior surface finish; conventional milling avoids dragging tools over abrasive outer scale and prevents leadscrew pulling.

Face Mill Lead Angles (90° vs. 45°) & Chip Thinning

• Identification: 90° shoulder cutters vs. 45° beveled edge cutters.

• When to Use: 90° when milling against square vertical walls; 45° for open surface face milling.

• Why: A 45° lead angle induces chip thinning (thins chip to ~70% of table feed), allowing higher feed rates, lower cutting temperatures, and less edge breakout on workpiece exit.

Milling Defects: Feed Marks, Back Striking, and Burrs

• Identification:

• Feed Marks: Scalloped feed wave patterns on the surface.

• Back Striking: Secondary scratches caused by trailing teeth dragging over the cut surface.

• Burrs: Thin plastically deformed metal ridges along exit edges.

• When to Use / Observe: Inspected during milling quality control.

• Why: Feed marks are reduced with wiper inserts; back striking is prevented by tramming the spindle with a slight tilt; burrs require deburring or chamfering passes.

Planing vs. Shaping vs. Broaching

• Identification:

• Planing: Large workpiece reciprocates past a stationary single-point tool.

• Shaping: Single-point tool reciprocates on a ram across a stationary workpiece.

• Broaching: Long multi-tooth bar tool with progressively taller teeth pulled or pushed through the part in one stroke.

• When to Use: Planing for huge machine tool ways/bases; Shaping for low-volume keyways and splines; Broaching for high-volume internal splines, keyways, and rifle bolt slots.

• Why: Planing and shaping require minimal tooling investment for low volume; broaching produces finished complex internal geometries in a single fast stroke