Manufacturing Processes, Tool Technology, and Metal Machining

Comprehensive review flashcards covering cutting tool technology, powder metallurgy, bulk forming, plastics, sheet forming, metal cutting theory, machine tool mechanisms, and high speed machining.

What are the three principal modes of cutting tool failure?

1. Fracture failure (excessive and/or dynamic cutting force leading to brittle fracture), 2. Temperature failure (cutting temperature is too high for the tool material), and 3. Gradual wear (gradual wearing of the cutting tool, which is the preferred mode).

Where do the two primary types of gradual wear occur on a cutting tool?

Crater wear occurs on the top rake face of the tool, while flank wear occurs on the flank (side of the tool).

In the tool flank wear ($\text{FW}$) versus cutting time curve, what are the three distinct regions of wear progression?

1. Break-in period (characterized by rapid initial wear), 2. Steady-state wear region (characterized by a uniform wear rate), and 3. Failure region (characterized by an accelerating wear rate leading to final failure).

What is the Taylor Tool Life Equation, and what do its terms represent?

$v T^n = C$, where $v$ is cutting speed, $T$ is tool life, $n$ is the slope of the natural log-log plot (dependent on feed, depth of cut, and materials), and $C$ is the intercept on the speed axis at a $1\,\text{min}$ tool life.

What are the typical criteria used in production to identify the end of tool life?

Complete failure of cutting edge, visual inspection of wear by the operator, fingernail test across cutting edge, changes in sound emitted from the operation, chips becoming stringy and difficult to dispose, degradation of surface finish, increased power, workpiece count, and cumulative cutting time.

What is the typical chemical composition of Grade T1 High Speed Steel (HSS)?

$18\%\,\text{W}$ (Tungsten), $4\%\,\text{Cr}$ (Chromium), $1\%\,\text{V}$ (Vanadium), and $0.9\%\,\text{C}$ (Carbon).

How do steel-cutting carbide grades differ in composition and wear resistance from nonsteel-cutting carbide grades?

Nonsteel grades consist only of $\text{WC-Co}$. Steel-cutting grades substitute titanium carbide ($\text{TiC}$) and/or tantalum carbide ($\text{TaC}$) for some tungsten carbide, which increases crater wear resistance for steel cutting but adversely affects flank wear resistance in nonsteel cutting.

What are the seven elements that define a single-point tool geometry signature convention in standard order?

Back rake angle ($\alpha_b$), side rake angle ($\alpha_s$), end relief angle ($\text{ERA}$), side relief angle ($\text{SRA}$), end cutting edge angle ($\text{ECEA}$), side cutting edge angle ($\text{SCEA}$), and nose radius ($\text{NR}$).

How do indexable cutting insert shapes compare in terms of strength versus versatility?

Round and square inserts possess the highest strength, highest power requirements, and greatest vibration tendency. As point angle sharpens down through triangles to $35^\circ$ rhombuses, strength decreases while versatility and accessibility increase.

Why does no actual cutting action take place at the central point of a standard twist drill?

Because relative velocity at the drill point is zero due to its zero distance from the axis of rotation; instead of cutting, a large thrust force is required to drive the chisel edge forward into the hole.

What type of drill is depicted, and what features make it suitable for deep-hole drilling?

A gun drill; it features a carbide cutting edge, a single straight flute, and an internal coolant hole running its entire length to deliver high-pressure cutting fluid directly to the cutting point.

What are the two primary classes of cutting fluids, and when is each most effective?

Coolants are water-based fluids most effective at high cutting speeds where heat generation is high and with tool materials susceptible to temperature failure (such as HSS); lubricants are oil-based fluids most effective at lower cutting speeds to reduce friction.

What are the four main steps in powder metallurgy?

1. Powder production, 2. Blending/mixing, 3. Compaction, and 4. Sintering.

What is sintering in powder metallurgy?

A heat treatment process conducted at temperatures below the melting point of the base metal that bonds compacted powder particles together via solid-state diffusion, transforming the green compact into a coherent, high-strength part.

What is impregnation in powder metallurgy?

The introduction of oil, liquid lubricant, or polymer into the inherent porous network of a sintered powder metal component, commonly utilized to fabricate self-lubricating bearings and gears.

How does metal working friction differ from mechanical friction?

Mechanical friction involves elastic contact between rigid mating bodies obeying Coulomb's law ($F = \mu N$), whereas metal working friction occurs under extreme normal pressures causing plastic deformation of the workpiece with sticking friction across the tool-work interface.

What is the primary difference between hot working and cold working in metal forming?

Hot working is performed above the recrystallization temperature of the metal, avoiding strain hardening and enabling large plastic deformations at lower forces; cold working is performed below recrystallization temperature, resulting in strain hardening, higher part strength, and superior surface finish.

What are the four classifications of hot worked processing?

1. Primary processing, 2. Secondary processing, 3. Bulk processing, and 4. Sheet forming.

How does impression die forging work?

A metal billet is compressed between shaped die halves containing cavities; the metal flows to fill the cavity shape while excess material is forced outward into a narrow gap to form flash, which cools rapidly and forces the remaining metal into deep cavity details.

How does metal extrusion work?

A work billet is placed in an extrusion container and pushed under high compressive force through a die orifice, causing the metal to plastically deform and emerge with a constant cross section defined by the die opening.

What is the key difference between thermoplastic and thermosetting plastics?

Thermoplastics consist of linear or branched polymer chains that can be repeatedly melted, softened, and reshaped by heating; thermosetting plastics undergo permanent chemical cross-linking during curing and decompose or char rather than melting upon reheating.

How does plastic injection molding operate?

Polymer pellets are fed into a heated barrel, melted and mixed by a rotating reciprocating screw, and then injected under high pressure into a closed, cooled mold cavity where the material solidifies into the final component geometry.

What is the operational difference between blanking and piercing in sheet metal shearing?

In blanking, the punched-out sheet piece is the desired part (the blank) and the surrounding sheet is scrap; in piercing (punching), the surrounding sheet is the desired part and the punched-out piece (slug) is scrap.

What is fine blanking, and how does it differ from standard shearing?

A precision sheet shearing process that utilizes a V-shaped impingement ring (stinger) to lock the sheet, a counter-punch, and extremely small tool clearances ($\sim 1\%$ of sheet thickness) to produce smooth, perpendicular edges completely free of fracture zones.

How does the tube hydroforming process work?

A tubular metal blank is loaded into a closed die cavity and expanded outward to match complex die contours using high internal liquid pressure combined with coordinated axial compressive feed from end punches.

What is High Energy Rate Forming (HERF)?

A group of sheet metal forming processes that deform workpieces at very high strain rates in microseconds using rapid energy releases, including explosive forming, electrohydraulic forming, and electromagnetic forming.

What is a transfer press in sheet metal forming?

A single automated multi-station stamping press where a workpiece is fed into the first station and sequentially moved across multiple distinct die stations by synchronized mechanical transfer fingers at every press cycle.

What is the difference between butt welding and lap welding?

In butt welding, the two workpieces lie in the same plane and are joined edge-to-edge; in lap welding, the two workpieces overlap each other at the joint area.

What are the three main families of material removal processes?

1. Conventional machining (material removal by a sharp cutting tool, such as turning, milling, and drilling), 2. Abrasive processes (material removal by hard abrasive particles, such as grinding), and 3. Nontraditional processes (material removal using mechanical, electrochemical, thermal, or chemical energy forms without a conventional cutting tool).

How is the chip thickness ratio $r$ defined in orthogonal cutting, and why is its value always less than $1.0$?

$r = \frac{t_o}{t_c}$, where $t_o$ is chip thickness before cut and $t_c$ is chip thickness after separation; it is always less than $1.0$ because plastic shear deformation during chip formation causes the cut chip thickness to always exceed the uncut chip thickness ($t_c > t_o$).

What type of chip formation is shown, and what cutting conditions produce it?

A serrated chip (saw-tooth appearance), characterized by alternating zones of high shear strain and low shear strain; it typically forms when machining difficult-to-machine metals (e.g., titanium alloys) at high cutting speeds.

Which forces acting on a cutting tool in orthogonal cutting can be measured directly with a dynamometer?

Cutting force ($F_c$), which acts in the direction of cutting speed, and thrust force ($F_t$), which acts perpendicular to cutting force in the direction of tool feed.

What is the Merchant Equation, and what adjustments increase the shear plane angle $\phi$?

$\phi = 45^\circ + \frac{\alpha}{2} - \frac{\beta}{2}$, derived on the principle that the work material selects a shear plane angle that minimizes cutting energy; the shear plane angle is increased by increasing the tool rake angle ($\alpha$) and reducing the friction angle ($\beta$) or coefficient of friction.

How is specific energy ($U$) in machining related to unit power ($P_u$) and cutting force ($F_c$)?

$U = P_u = \frac{P_c}{R_{MR}} = \frac{F_c v}{v t_o w} = \frac{F_c}{t_o w}$, representing the cutting energy required per unit volume of material removed, typically expressed in $\text{N}\cdot\text{m}/\text{mm}^3$ or $\text{J}/\text{mm}^3$.

What percentage of cutting energy is converted into heat during metal machining, and where does the remaining energy go?

Approximately $98\%$ of the machining energy is converted directly into heat at the shear zone and tool-chip interface; the remaining $\sim 2\%$ is retained as elastic strain energy within the chip.

What is the difference between generating and forming in creating part geometry during machining?

In generating, the part geometry is determined by the trajectory of the tool's feed motion (e.g., straight turning, contour turning, plain milling); in forming, the part geometry is created directly by the profile shape of the cutting tool edge (e.g., form turning, gear form-milling, threading die).

How does the collet workholding mechanism shown clamp a cylindrical workbar?

An outer tapered sleeve advances axially forward over the collet, squeezing its three flexible longitudinal slits radially inward to securely clamp the workbar.

What are the three hole-finishing operations depicted in (d), (e), and (f)?

(d) Countersinking (machining a cone-shaped entrance into a hole), (e) center drilling (drilling a starting hole for subsequent operations or mounting between centers), and (f) spot facing (machining a flat, smooth bearing surface perpendicular to a hole axis).

How do shaping and planing differ in terms of their speed and feed motions?

In shaping, the single-point tool reciprocates linearly to create the cutting speed motion while the worktable feeds intermittently; in planing, the workpart reciprocates on a worktable to generate the cutting speed motion while the toolhead feeds intermittently across the crossrail.

What is the structural difference between external broaching and internal broaching?

In external broaching (a), the cutting tool moves along the outer perimeter of the workpart to create contours or slots; in internal broaching (b), a stepped-tooth broach is pulled or pushed through an internal starting hole to form keyways, splines, or geometric shapes.

How are gear teeth produced using the form-milling cutter depicted?

The form-milling cutter has teeth ground to match the exact profile of the space between adjacent gear teeth; it cuts one space along the gear face width, and the gear blank is indexed (rotated by one tooth pitch) between passes until all teeth are formed.

How are the DN ratio and hp/rpm ratio defined for High Speed Machining (HSM)?

The $\text{DN}$ ratio equals bearing bore diameter ($\text{mm}$) multiplied by maximum spindle speed ($\text{rev/min}$), typically ranging from $500{,}000$ to $1{,}000{,}000$ for HSM. The hp/rpm ratio measures horsepower relative to maximum speed, with HSM operations dividing at or below $0.005\,\text{hp/rpm}$.