Q1. What is welding? Describe a few solid-state welding processes.

Ans: Welding is the process of permanently joining two materials (usually metals) using heat, pressure, or both.
In solid-state welding, the materials are joined without melting. Examples:

 Friction Welding: Heat is produced by rubbing two parts and then applying pressure.
 Ultrasonic Welding: High-frequency sound vibrations + pressure used for plastics and thin metals.
 Diffusion Welding: High temperature and pressure cause atoms to bond — used in aerospace.

Q2. What is GMAW, JAW, TIG, and MIG welding? Describe process and application.
Ans:

 GMAW (Gas Metal Arc Welding): Uses wire electrode + shielding gas. Common in car
manufacturing.
 TIG (Tungsten Inert Gas): Uses tungsten electrode, no filler. Very clean, used in aerospace.
 MIG (Metal Inert Gas): Similar to GMAW. Easy for beginners, used in home and auto repair.
 JAW is likely a misprint. You might mean SMAW (Shielded Metal Arc Welding) – uses flux-coated
rods, used in construction.

Q3. What are welding transformer characteristics? How do arc voltage/current affect weld bead?
Ans:

 Transformer: Converts high-voltage, low-current into low-voltage, high-current.

 High Current: Deep, narrow weld but risk of burn-through.
 High Voltage / Long Arc: Wider bead but less penetration and more spatter.

Q4. Differences between AC and DC welding machines?

Feature AC Welding DC Welding

Arc Stability Less stable More stable
Cost Cheaper More expensive
Use Thick metals, rusted parts Thin metals, smoother finish
Polarity Alternates Fixed (straight/reverse)

Q5. Ingredients and functions of flux in AC welding electrode coating?

Ans:
Ingredients: Rutile, cellulose, iron oxide, silicates.
Functions:

 Forms gas shield to protect molten weld from air.

 Creates slag that covers the weld and prevents oxidation.
 Helps stabilize arc and improve weld strength.

Q6. How is underwater welding done? Applications?

Ans:

 Dry Welding: Chamber filled with gas is sealed around the weld zone.
  Wet Welding: Weld done directly in water using special waterproof electrodes.
Applications: Ship hull repairs, underwater pipelines, oil rigs.

Q7. What are special welding processes? Describe laser, plasma, and ultrasonic welding.
Ans:

 Laser Welding: Focused light beam melts metal. High speed and precision – used in electronics,
aerospace.
 Plasma Arc Welding: Similar to TIG but with hotter, faster plasma arc – used for thick plates.
 Ultrasonic Welding: Sound vibrations at 20kHz+ create friction – used in plastics and small parts.

Q8. Which welding is used for aircraft and ships? Explain.

Ans:

 Aircraft: TIG and Laser welding – accurate and clean for aluminum, titanium.
 Ships: MIG and Submerged Arc Welding (SAW) – faster, deeper welds for thick steel plates.
(You can draw two sketches: a TIG torch and a SAW setup)

Q9. Explain oxyacetylene flames with a diagram.

Ans:
Three flame types in gas welding:

 Neutral Flame (1:1): Ideal for most metals.

 Carburizing Flame (More acetylene): Used for high-carbon steel.
 Oxidizing Flame (More oxygen): Used for brass and cutting.
(Draw flame with inner, intermediate, and outer zones)

Q10. Applications of Submerged Arc Welding (SAW)?

Ans:

 Used in heavy fabrication: shipbuilding, pressure vessels, pipelines.

 Benefits: Deep weld, low spatter, high speed. Fully automatic.

Q11. Welding in space (no atmosphere)?

Ans:

 In vacuum, metals can weld naturally if clean – called cold welding.

 For actual tasks, diffusion bonding or laser welding inside pressurized chambers is used.

Q12. Tools used in welding (with diagram):

 C-Clamp: Holds metal pieces firmly during welding.

 Electrode Holder: Carries current and holds the electrode stick.
  Wire Brush: Cleans slag and oxidation from welded area.
(Draw each tool simply for quick recall)

Q13. What do you understand by the fitting process?

Ans: The fitting process involves assembling, adjusting, and finishing metal parts to achieve the desired
dimensions and functionality. It includes operations like filing, drilling, tapping, and reaming to ensure precise
fits.

Q14. What are the various types of vices used in the fitting process? Explain V-block.
Ans: Common types of vices include:Mech Lesson+1www.slideshare.net+1

 Bench Vice: Used for general-purpose holding of workpieces.

 Pipe Vice: Designed to hold cylindrical objects like pipes.
 Hand Vice: Portable vice for small workpieces.
 Leg Vice: Heavy-duty vice mounted on a leg for blacksmithing.Crescent Tools

V-Block: A V-shaped block used to hold cylindrical workpieces securely during marking or drilling.

Diagram of a V-Block:

Q15. What do you understand about die stock and tap drills with respect to fitting?
Ans: Die stock is a tool used to hold and rotate dies for cutting external threads on rods. Tap drills are used to
create internal threads by cutting into pre-drilled holes using taps.

Q16. Explain the geometry of the hacksaw blade used in the hacksaw machine.
Ans: A hacksaw blade has:

 Length: Typically 10 to 12 inches.

 Teeth per Inch (TPI): Ranges from 14 to 32; higher TPI for finer cuts.
 Tooth Set: Alternating teeth bent outward to prevent binding.Pinterest+3The Spruce+3Scribd+3Better
Homes & Gardens

Diagram of a Hacksaw Blade:Difference Box+2Better Homes & Gardens+2Redbox Tools+2

Q17. How does a power hacksaw work? Explain with a diagram.

Ans: A power hacksaw uses an electric motor to drive a reciprocating saw blade for cutting metal. The
mechanism converts rotary motion into linear motion to move the blade back and forth.

Diagram of a Power Hacksaw:

Q18. Explain various tools of the fitting shop with diagrams.
Ans: Fitting shop tools include:Scribd+2www.slideshare.net+2Log in or sign up to view+2

 Marking Tools: Scriber, center punch.

 Measuring Tools: Steel rule, calipers.
 Cutting Tools: Hacksaw, chisels.
 Holding Tools: Bench vice, clamps.
 Striking Tools: Ball peen hammer.Amazon+1YouTube+1JCBL Hand ToolsLog in or sign up to
view+1Redbox Tools+1

Diagram of Fitting Shop Tools:Log in or sign up to view+2Scribd+2www.slideshare.net+2

Q19. What is a boring process? How does it differ from drilling? Explain the twisted drill bit for drilling.
Ans: Boring enlarges existing holes with high precision, while drilling creates new holes. A twist drill bit has
helical flutes to remove material and a pointed tip for centering.

Diagram of a Twist Drill Bit:

Q20. Explain bench vice with a diagram.

Ans: A bench vice is a clamping device mounted on a workbench, consisting of fixed and movable jaws to hold
workpieces securely during operations.

Diagram of a Bench Vice:

Q21. Describe various types of drill machines used in fitting with diagrams and applications.
Ans: Types of drill machines:Technology Student

 Portable Drill: Handheld, used for light-duty tasks.

 Bench Drill: Mounted on a bench, suitable for small to medium workpieces.
 Pillar Drill: Floor-mounted, handles larger workpieces.
 Radial Drill: Arm can rotate and move, used for large and heavy workpieces.

Diagram of Drill Machines:

Q22. Explain with diagrams various types of hammers used in fitting.

Ans: Common hammers:

 Ball Peen Hammer: For metalworking.

 Cross Peen Hammer: For starting panel pins and tacks.
 Claw Hammer: For driving and removing nails.
 Sledgehammer: For heavy-duty tasks.Pinterest

Diagram of Hammers:
Q23. Explain with diagrams various types of files used in the fitting process.
Ans: Types of files:ResearchGate+12Technology Student+12Mech Lesson+12

 Flat File: For general-purpose filing.

 Half-Round File: For curved surfaces.
 Round File: For enlarging round holes.
 Square File: For filing square corners.
 Triangular File: For filing angles and corners.Wikipedia+2Technology Student+2Turntech
Precision+2

Diagram of Files:

Q24. What do you understand by height gauge and wire gauge in a fitting shop?
Ans: A height gauge measures vertical distances or marks items for machining. A wire gauge measures the
diameter of wires or thickness of sheet metal.

Diagram of Height Gauge:

Q25. Explain various types of steel used in fitting industrial applications.

Ans: Types of steel:Xometry+7Technology Student+7JCBL Hand Tools+7

 Carbon Steel: Used for general-purpose tools.

 Alloy Steel: Contains additional elements for improved properties.
 Stainless Steel: Corrosion-resistant, used in food and medical industries.
 Tool Steel: High hardness, used for cutting tools.

Diagram of Steel Types:Metal Supermarkets

Q26. What do you understand by a machine tool and a machine?

Ans: A machine is a device that performs work using mechanical power. A machine tool is a specific type of
machine used to shape or machine metal or other rigid materials, typically by cutting, boring, grinding, or
shearing.

Q27. Explain various functions (operations) of the lathe machine with diagrams.
Ans: A lathe machine performs several operations:Testbook+1www.slideshare.net+1

 Turning: Removing material from the outer diameter.

 Facing: Smoothing the end of the workpiece.
 Drilling: Creating holes using a drill bit.
 Boring: Enlarging existing holes.
 Threading: Cutting screw threads.

Diagram of Lathe Machine Operations:Testbook+4Scribd+4BOYI+4

Q28. How is a square thread made in a lathe machine? What is the tool used for thread cutting in a lathe
machine?
Ans: Square threads are cut using a single-point cutting tool with a square-shaped profile. The lathe is set to the
desired pitch, and multiple passes are made to achieve the required depth.
Q29. What is a single-point cutting tool? Describe its various angles and its uses with diagrams.
Ans: A single-point cutting tool has one cutting edge and is used in lathes. Key angles include:

 Rake Angle: Influences chip flow.

 Clearance Angle: Prevents tool from rubbing.
 Cutting Edge Angle: Determines the direction of cutting.Mech Lesson+8Testbook+8Mechanical
Jungle+8Esskay Machines+6YouTube+6Pinterest+6

Diagram of Single-Point Cutting Tool Angles:

Q30. What is the application of a milling machine? Describe its various types and applications for
individuals.
Ans: Milling machines are used to remove material from a workpiece by feeding it against a rotating cutter.
Types include:Phillips Corporation

 Horizontal Milling Machine: Spindle is horizontal; used for heavy-duty tasks.

 Vertical Milling Machine: Spindle is vertical; suitable for precision work.
 Universal Milling Machine: Can be adjusted for various operations.

Diagram of Milling Machine Types:

Q31. What is the tool material used in a grinding wheel? Describe its composition.
Ans: Grinding wheels are made from abrasive grains bonded together. Common materials include:

 Aluminum Oxide: For steel and ferrous metals.

 Silicon Carbide: For non-ferrous metals.
 Diamond: For hard materials like ceramics.The Engineering Choice+1HubPages+1

Q32. What is the use of a multi-point cutting tool used in a milling machine?
Ans: Multi-point cutting tools, like milling cutters, have multiple cutting edges, allowing for faster material
removal and smoother finishes compared to single-point
tools.www.slideshare.net+12www.slideshare.net+12Mech Lesson+12

Q33. What are the different components of a lathe machine? Explain with a diagram.
Ans: Main components include:Market Prospects+6Scribd+6Reverse Engineering+6

 Bed: Base of the machine.

 Headstock: Houses the spindle.
 Tailstock: Supports the other end of the workpiece.
 Carriage: Holds and moves the cutting tool.HubPagesAmerican Machine Tools+12nakamura-
tome.com+12Scribd+12

Diagram of Lathe Machine Components:YouTube

Q34. What are the different components of a milling machine and shaper machine? Explain with
diagrams.
Ans: Milling Machine Components:

 Base: Supports the machine.

 Column: Houses the spindle and motor.
 Knee: Supports the saddle and table.
 Saddle: Holds the table.
 Table: Holds the workpiece.www.slideshare.net+9Mechanical Booster+9Scribd+9

Diagram of Milling Machine Components:

Shaper Machine Components:

 Base: Foundation of the machine.

 Column: Vertical support.
 Ram: Holds the tool and moves back and forth.
 Table: Holds the workpiece.Pinterest+5Mechanical Jungle+5Reverse Engineering+5Esskay
Machines+4The Engineering Choice+4YouTube+4

Diagram of Shaper Machine Components:

Q35. What is tailstock, indexing machine tool post, lead screw, gear box used in lathe machine?
Ans:

 Tailstock: Supports the end of the workpiece and can hold tools like drills.
 Indexing Machine Tool Post: Allows quick tool changes at set angles.
 Lead Screw: Drives the carriage for threading operations.
 Gearbox: Provides various speed and feed combinations.Mechanical
Booster+7Scribd+7leblondusa.com+7Mechanical Booster

Q36. What is the function of a shaper machine? Describe its type and how it's different from planner
machines.
Ans: A shaper machine uses a single-point cutting tool that moves linearly to cut material. Types include:Mech
Lesson+5YouTube+5Market Prospects+5

 Horizontal Shaper: Tool moves horizontally.

 Vertical Shaper: Tool moves vertically.Pinterest+9leblondusa.com+9Wikipedia+9

Difference from Planner Machine:

 Shaper: Tool moves; workpiece is stationary.

 Planner: Workpiece moves; tool is stationary.

Q37. Describe various types of coolant used in various machine tools. What are its ingredients?
Ans: Coolants reduce heat and friction. Types include:

 Water-Based Coolants: Water mixed with oils and additives.

 Oil-Based Coolants: Mineral oils with additives.
  Synthetic Coolants: Chemical-based, no oil.

Ingredients:

 Lubricants: Reduce friction.

 Corrosion Inhibitors: Prevent rust.
 Biocides: Prevent microbial growth.

Q38. What is the Whitworth mechanism in a shaper machine? Describe it with diagrams.
Ans: The Whitworth mechanism converts rotary motion into reciprocating motion with a quick return stroke,
increasing efficiency.

Diagram of Whitworth Mechanism:

Q39. What do you understand by computerized numeric control machine (CNC)? How does it work?
Explain a few steps of its programme. What is the G90 code? Work on a CNC machine.
Ans: A CNC machine uses computer programs to control machine tools. It operates by reading G-code
instructions.

Steps:

1. Design the part using CAD software.

2. Convert the design to G-code using CAM software.
3. Load the G-code into the CNC machine.
4. Machine executes the code to produce the part.

G90 Code: Sets the machine to absolute positioning mode.

Q40. Explain semi-automatic, automatic, and manual machines with respect to milling operations.
Ans:

 Manual Machines: All operations are performed by the operator.

 Semi-Automatic Machines: Some functions are automated; operator intervention is still required.
 Automatic Machines: All operations are automated with minimal operator involvement.

1.

Key Questions
Q3. Transformer Characteristics & Arc Effects
o Transformer Basics: Steps down 11 kV→40 V while boosting current to 100s of amperes.
o Arc Voltage: Affected by arc length (≈1 V/mm). Longer arc → higher voltage → wider,
flatter bead, more spatter.
o Arc Current: Controls penetration depth.
 Low current (50–100 A): Shallow bead, good for thin sections.
 High current (200–400 A): Deep penetration, risk of burn-through.
o Example: Welding a 5 mm plate at 120 A gives a 3 mm penetration; at 200 A it’s ~5 mm.
2. Q4. AC vs DC Welding Machines

Feature AC DC
Arc Stability Pulsating (50 Hz), more spatter Smooth, less spatter
 Feature AC DC
Electrode
Only cellulose/oxidizing flux rods Rutile, titania, iron-powder rods
Options
Electrode positive (→ shallow) or negative (→
Polarity Use No straight polarity → no arc blow
deep)
Heavy rusted sections, pipeline
Typical Use Precision work, thin sheet metal
work

3. Q5. Flux Ingredients & Functions

o Rutile (TiO₂): Stabilizes arc → smooth, spray-type bead.
o Cellulose: Produces CO₂ → excellent penetration, deep-type bead.
o Iron Powder: Increases deposition rate by adding metal to the weld.
o Silicates & Fluorides: Fluxing agents that cleanse oxides and deoxidize molten metal.
o Function Summary:
1. Generate protective slag layer
2. Create inert gases to shield the arc
3. Modify bead shape and mechanical properties
4. Q7. Special Welding Processes
o Laser Welding:
 Power Density: 10⁶–10⁸ W/cm²
 Penetration: 0.5–10 mm in single pass
 Uses: Micro-electronics, medical implants
o Plasma Arc Welding (PAW):
 Arc Temp: >15,000 °C
 Key Feature: Constricted arc → deeper penetration than TIG
 Uses: Aerospace alloy, thick sections
o Ultrasonic Welding:
 Frequency: 20–70 kHz
 Pressure: 0.1–5 MPa
 Uses: PVC pipes, battery tabs, textile laminations
5. Q9. Oxy-Acetylene Flame Types (Detail)
o Neutral Flame (1:1): Inner cone ~5 mm, temp ≈3,150 °C
o Carburizing Flame: Feather extends 10–15 mm, temp ≈2,600 °C
 Leaves carbon on weld → useful for build-up or hard facing
o Oxidizing Flame: Inner cone small, temp ≈3,200 °C
 Burns oxides off brass/copper; not for steel (forms brittle iron oxide)
6. Q11. Welding in Vacuum/Space
o Cold Welding: Two clean metal surfaces pressed in vacuum → atomic bonding with no heat.
o Diffusion Bonding in Space Chambers:
 Pressures ~0.1–1 MPa, temperatures 0.5 Tm (Tm = melting temp)
 Used for satellite component assembly
o Challenges: Outgassing, thermal control, lack of shielding gas
7. Q17. Power Hacksaw Working Principles
o Mechanism: Crank‐slider converts motor’s rotary motion into blade’s reciprocation.
o Feed Control: Hydraulic ram applies constant feed pressure (~2–5 kN).
o Cutting Parameters:
 Blade speed: 20–60 m/min (depending on material)
 Stroke length: 50–75 mm
o Example Application: Cutting 50 mm mild-steel bar at 40 m/min and 4 kN feed.
8. Q27. Lathe Operations Detailed
o Turning: Rough vs finish—rough uses >0.5 mm depth of cut, finish ≈0.1 mm.
o Facing: Feed rate ≈0.1–0.3 mm/rev, used to square ends.
o Parting (Cut-off): Uses a narrow tool, feed ≈0.05 mm/rev to avoid chatter.
o Knurling: Produces diamond pattern; tool feed locked to spindle.
9. Q33. Lathe Machine Components & Their Roles
o Bed: Cast-iron, dampens vibration.
o Headstock: Contains gear train for spindle speeds (50–3,000 rpm).
o Carriage:
 Cross‐slide: Perpendicular feed (0.05–0.5 mm/rev).
  Compound Rest: Angular cuts, threading.
o Lead Screw vs Feed Rod:
 Lead screw for threading (single‐start, half‐nut engagement).
 Feed rod for sliding and surfacing feeds.
10. Q39. CNC Basics & G90 Code

 CNC Workflow: CAD → CAM → G-code → Machining → Inspection.

 Sample G-code Steps:

gcode
CopyEdit
G21 ; Units in mm
G90 ; Absolute positioning
G0 X0 Y0 ; Rapid move to origin
G1 Z-5 F100 ; Linear cut at 100 mm/min
G2 X20 Y20 I10 J0 ; Clockwise arc
M30 ; Program end

 G90 vs G91:
o G90 (Absolute): Coordinates from program zero.
o G91 (Incremental): Each move relative to current position.

VIVA PREPARATION: WELDING, FITTING & MACHINE SHOP

🔧 WELDING JOB

Q1. What is welding? Describe solid-state welding processes.

Ans: Welding permanently joins metals using heat, pressure, or both. In solid-state welding, parts are joined
without melting. Examples:

 Friction Welding: Heat from rubbing + pressure.

 Ultrasonic Welding: High-frequency vibrations + pressure (electronics).
 Diffusion Welding: High temperature & pressure over time (aerospace).

Q2. GMAW, SMAW, TIG, MIG—Process & Applications.

 GMAW (Gas Metal Arc Welding/MIG): Continuous wire + shielding gas; automotive & fabrication.
 SMAW (Shielded Metal Arc Welding): Flux-coated rods; construction & maintenance.
 TIG (Tungsten Inert Gas): Non-consumable tungsten electrode; precise, aerospace & stainless steel.
 MIG: Same as GMAW; thin sheets & beginner-friendly.

Q3. Welding Transformer & Arc Effects.

 Steps down 11 kV→40 V, boosts current to 100s A.

 Arc Voltage (V/mm): Longer arc → ↑voltage → wider, flatter bead & more spatter.
 Arc Current: Controls penetration: low (thin plates), high (deep weld, burn-through risk).

Q4. AC vs DC Welding Machines.

 Feature AC DC
Arc Stability Pulsating (50 Hz), more spatter Smooth, less spatter
Cost Cheaper More expensive
Use Thick, rusted parts Thin metals, out-of-position work
Polarity Alternates Straight/reverse

Q5. Flux Ingredients & Functions (AC).

 Ingredients: Rutile (TiO₂), cellulose, iron powder, silicates.

 Functions: Create gas shield, form protective slag, stabilize arc, add alloying elements.

Q6. Underwater Welding & Applications.

 Dry Welding: Sealed chamber with inert gas.

 Wet Welding: Waterproof electrodes directly in water.
 Applications: Ship hulls, pipelines, offshore rigs.

Q7. Special Welding Processes.

 Laser Welding: 10⁶–10⁸ W/cm²; penetration 0.5–10 mm; electronics & medical devices.
 Plasma Arc Welding: >15 000 °C, constricted arc; aerospace & thick sections.
 Ultrasonic Welding: 20–70 kHz vibrations; plastics, battery tabs.

Q8. Welding in Aircraft & Ships.

 Aircraft: TIG & laser (aluminum, titanium) for precision.

 Ships: MIG & SAW (thick steel) for speed & deep welds.

Q9. Oxy-Acetylene Flame Types.

 Neutral (1:1): ~3 150 °C, general purpose.

 Carburizing (>C₂H₂): ~2 600 °C, adds carbon for build-up.
 Oxidizing (>O₂): ~3 200 °C, for brass/copper.

Q10. Submerged Arc Welding (SAW) Applications.

Heavy fabrication: bridges, pressure vessels, shipbuilding & tanks. Automatic, deep & clean welds.

Q11. Welding in Space (Vacuum).

 Cold Welding: Clean metals bond under pressure; no heat needed.

 Diffusion Bonding: 0.1–1 MPa, 0.5 Tm; used in vacuum chambers.

Q12. Welding Tools.

 C-Clamp: Holds workpieces.

 Electrode Holder: Grips rod & conducts current.
 Wire Brush: Removes slag.

🛠️ FITTING PROCESS

Q13. Fitting Process.

Assembling, adjusting & finishing metal parts by filing, drilling, tapping & reaming for precise fits.
Q14. Vices & V-Block.

 Types: Bench, pipe, hand, leg vice.

 V-Block: V-shaped block for holding cylindrical pieces.

Q15. Die Stock & Tap Drill.

 Die Stock: Holds dies for external threads.

 Tap Drill: Prepares holes for internal threads.

Q16. Hacksaw Blade Geometry.

 Length: 250–300 mm.

 TPI: 14–32 (higher for finer cuts).
 Tooth Set: Alternating to prevent binding.

Q17. Power Hacksaw Operation.

Motor-driven crank-slider → blade reciprocation; hydraulic feed (2–5 kN); 20–60 m/min blade speed.

Q18. Fitting Shop Tools.

 Marking: Scriber, punch.

 Measuring: Rule, calipers.
 Cutting: Hacksaw, chisels.
 Holding: Vice, clamps.
 Striking: Ball peen hammer.

Q19. Boring vs Drilling & Twist Drill Bit.

 Drilling: Creates hole.

 Boring: Enlarges hole with accuracy.
 Twist Drill: Helical flutes for chip removal.

Q20. Bench Vice.

Fixed + movable jaws on bench for clamping.

Q21. Drill Machines.

 Portable, Bench, Pillar, Radial with increasing capacity.

Q22. Hammers.
Ball peen, cross peen, claw, sledge.

Q23. Files.
Flat, half-round, round, square, triangular.

Q24. Gauges.

 Height Gauge: Vertical measurement/marking.

 Wire Gauge: Measures wire/sheet diameter.

Q25. Steels.
Carbon, alloy, stainless, tool steel.
⚙️ MACHINE SHOP

Q26. Machine vs Machine Tool.

 Machine: Performs work (power-driven).

 Machine Tool: Shapes material by cutting.

Q27. Lathe Operations.

Turning, facing, drilling, boring, threading, parting, knurling.

Q28. Square Threads & Tool.

Single-point square-profile tool; multiple passes at pitch setting.

Q29. Single-Point Tool Angles.

Rake, clearance, cutting-edge angles control chip flow & friction.

Q30. Milling Machines.

Horizontal (heavy cuts), vertical (precision), universal (versatile).

Q31. Grinding Wheel Materials.

Al₂O₃ (steel), SiC (non-ferrous), diamond (ceramics).

Q32. Multi-Point Tools.

Milling cutters with many edges → faster, smoother finishes.

Q33. Lathe Components.

Bed, headstock, tailstock, carriage (cross-slide, compound), lead screw, feed rod.

Q34. Milling & Shaper Components.

 Milling: Base, column, knee, saddle, table.

 Shaper: Base, column, ram, table.

Q35. Lathe Accessories.

Tailstock, tool post (indexing), lead screw (threading), gearbox (speeds/feeds).

Q36. Shaper vs Planner.

Shaper: tool moves.
Planner: workpiece moves.

Q37. Coolants.
Water-based, oil-based, synthetic.
Ingredients: Lubricants, inhibitors, biocides.

Q38. Whitworth Mechanism.

Crank + slotted link for quick-return reciprocation.

Q39. CNC Basics & G90.

CAD → CAM → G-code → machine.
G90: absolute positioning.
Sample:

G21; mm
G90; abs
G0 X0 Y0
G1 Z-5 F100
M30

Q40. Manual, Semi-Auto & Auto Milling.

 Manual: Operator controls all.

 Semi-Auto: Some automation (feeds/spindle).
 Auto: Fully programmed.

🔑 DETAILED ANSWERS TO KEY QUESTIONS

Below are expanded answers with added examples and diagrams where indicated.

1. Transformer Characteristics & Arc Effects (Q3)

 Transformer Function: Steps 11 kV down to ~40 V, boosting current to hundreds of amperes for
welding.
 Arc Voltage (~1 V/mm): Longer arc length increases voltage; results in a wider, flatter bead and more
spatter.
 Arc Current: Controls penetration depth:
o Low current (50–100 A): Shallow penetration, ideal for thin plates.
o High current (200–400 A): Deep penetration, higher risk of burn-through.
 Example: Welding a 5 mm mild steel plate: 120 A yields ~3 mm penetration; 200 A yields ~5 mm.

2. AC vs DC Welding Machines (Q4)

Feature AC Welding DC Welding

Arc Stability Pulsating at 50 Hz → more spatter Smooth, steady arc → less spatter
Electrode Options Only cellulose/oxidizing flux rods Rutile, titania, iron-powder rods
Polarity Control Alternates → no polarity change needed Electrode Positive → shallow, Negative → deep
Typical Uses Thick, rusted sections; pipeline work Thin materials; out-of-position welding

3. Flux Ingredients & Functions (Q5)

 Rutile (TiO₂): Stabilizes arc → smooth, spray-type bead.

 Cellulose: Generates CO₂ → deep penetration (digging action).
 Iron Powder: Increases deposition rate (adds metal).
 Silicates/Fluorides: Clean oxides, deoxidize molten metal.

Functions Summary:

1. Form protective slag.

2. Generate shielding gases.
3. Stabilize arc.
4. Modify bead shape and mechanical properties.
4. Special Welding Processes (Q7)

 Laser Welding:
o Power Density: 10⁶–10⁸ W/cm².
o Penetration Depth: 0.5–10 mm per pass.
o Applications: Microelectronics, medical implants.
 Plasma Arc Welding (PAW):
o Arc Temperature: >15 000 °C, constricted column.
o Penetration: Deeper than TIG.
o Applications: Aerospace alloys, thick sections.
 Ultrasonic Welding:
o Frequency: 20–70 kHz vibrations under pressure.
o Applications: Plastic assemblies, battery tabs, textiles.

5. Oxy-Acetylene Flames (Q9)

Three flame types in gas welding:

 Neutral Flame (1:1 O₂: C₂H₂): ~3 150 °C; general purpose.

 Carburizing Flame (C₂H₂ > O₂): ~2 600 °C; deposits extra carbon for build-up.
 Oxidizing Flame (O₂ > C₂H₂): ~3 200 °C; removes oxides on brass/copper.

Diagram:

6. Welding in Space (Q11)

 Cold Welding: In vacuum, two clean metal surfaces pressed together bond at an atomic level without
heat.
 Diffusion Bonding (in chambers): 0.1–1 MPa pressure, ~0.5 Tm temperature; used for satellite parts.
 Challenges: No atmosphere → no shielding gases; outgassing of materials; thermal control.

7. Power Hacksaw Principles (Q17)

 Mechanism: Electric motor drives a crank-slider converting rotary motion into linear blade strokes.
 Feed Control: Hydraulic ram maintains constant pressure (2–5 kN).
 Parameters:
o Blade Speed: 20–60 m/min (material-dependent).
o Stroke Length: 50–75 mm.

Diagram:

8. Lathe Operations Details (Q27)

  Turning: Rough (depth >0.5 mm) vs finish (~0.1 mm); reduces diameter.
 Facing: Feed 0.1–0.3 mm/rev; squares off ends.
 Parting: Narrow tool, feed ~0.05 mm/rev to avoid chatter.
 Knurling: Diamond pattern; tool feed locked to spindle rotation.
 Drilling & Boring: Use tailstock for drill; follow with boring tool for precision.

Diagram:

9. Lathe Components & Roles (Q33)

 Bed: Cast iron, vibration damping.

 Headstock: Gear train, spindle speeds (50–3000 rpm).
 Tailstock: Supports free end; holds drills or reamers.
 Carriage Assembly:
o Cross-Slide: Perpendicular feed (0.05–0.5 mm/rev).
o Compound Rest: Angular cuts, threading.
 Lead Screw: Threading drive (single start, half-nuts).
 Feed Rod: Sliding/surfacing feed drives.

Diagram:

10. CNC Basics & G90 Code (Q39)

 Workflow: CAD → CAM → post-processor → CNC machine → part inspection.

 Sample G-Code:
 G21 ; Units in mm
 G90 ; Absolute positioning
 G0 X0 Y0 ; Rapid move to origin
 G1 Z-5 F100; Linear cut at 100 mm/min
 G2 X20 Y20 I10 J0 ; CW arc
 M30 ; Program end
 G90 vs G91:
o G90: Absolute – coordinates from program zero.
o G91: Incremental – coordinates relative to current position.

End of Document. Good luck with your viva!