Workshop 2024 beu

These are some common types of saws used in carpentry:

1. Hand Saw (Rip Saw):
   • Used for general cutting of wood.
   • Cuts along the grain (rip cut).
   • Has large and sharp teeth.
2. Crosscut Saw:
   • Used to cut across the wood grain.
   • Teeth are angled to make smooth cuts.
   • Suitable for trimming wood pieces.
3. Back Saw (Tenon Saw):
   • Has a stiff metal strip on the back for control.
   • Used for precise cutting, like joints.
   • Works well with a miter box.
4. Coping Saw:
   • Has a thin, narrow blade.
   • Ideal for cutting curves and intricate shapes.
   • Often used for decorative work.
5. Bow Saw:
   • Has a metal frame shaped like a bow.
   • Used for cutting rough wood and logs.
   • Best for outdoor work and pruning.
6. Panel Saw:
   • Shorter than a hand saw.
   • Used for cutting panels or small boards.
   • Easy to handle in tight spaces.
7. Compass Saw:
   • Has a narrow, tapered blade.
   • Used for cutting curves or holes inside wood.
   • Blade fits into tight areas.
8. Keyhole Saw (Pad Saw):
   • Long, narrow blade for cutting small holes.
   • Used for interior cutouts like switch boxes.

In sheet metal work, seams are used to join two or more sheets of metal together, especially in making containers like pipes, boxes, or ducts. These seams provide strength and leak-proof joints.

Types of seams in sheet metal operation:

1. Lap Seam:
   • One edge of the sheet overlaps the other and both are folded together.
   • Commonly used in cylindrical shapes like water tanks.
   • Good strength and moderately leak-proof.
2. Grooved Seam (Locked Seam):
   • Both edges are folded and interlocked together.
   • Used in round and square ducts.
   • Provides high strength and a tight joint.
3. Single Seam:
   • One edge is turned over the other and hammered or rolled flat.
   • Used in tin can manufacturing.
   • Less leak-proof than a double seam.
4. Double Seam:
   • Two folds are made and pressed tightly.
   • Very strong and leak-proof.
   • Common in food containers (cans).
5. Dovetail Seam:
   • Interlocking slots (like fingers) are cut and bent together.
   • Mostly used in box-type containers.
   • Looks like a puzzle joint.
6. Wired Edge Seam:
   • A wire is placed in the edge fold of the sheet and rolled in.
   • Gives rigidity and strength to the edge.
   • Common in bucket or tray rims.

Most Important Forging Operations:

1. Upsetting
   Increases the diameter by reducing length.
   Used in bolt head formation or thick ends.
2. Drawing Out (or Drawing Down)
   Increases length and reduces cross-section.
   Used for making long rods, axles, etc.
3. Fullering
   Used to distribute material before further forging.
   Forms grooves or depressions using fuller tools.
4. Punching
   Makes holes in heated metal using punch and hammer.
   Common in rivet hole making. //ONLY four
5. Edging
   Gathers metal into a desired shape at the edge.
   Prepares metal for drawing or bending.
6. Bending
   Simple operation to give angular shape to metal.
   Done on anvils or special bending tools.

Tape is a flexible strip or roll of material (plastic, paper, or fabric) coated with adhesive on one or both sides.
It is used in fitting operations for marking, sealing, joining, insulating, or protecting surfaces and components.

Different Types of Tape Used in Fitting:

1. Measuring Tape

• Made of steel or plastic strip with graduated markings.
• Used to measure length, height, width of components.
• Essential in fitting and fabrication works.

2. Insulation Tape (Electrical Tape)

• Made of vinyl or plastic and used for electrical insulation.
• Comes in different colors.
• Prevents short circuits and protects exposed wires.

3. Masking Tape

• Light adhesive paper tape used during painting or surface marking.
• Easy to remove without damaging the surface.
• Common in workshops and painting areas.

4. Thread Seal Tape (Teflon Tape/PTFE Tape)

• White, non-sticky tape used to seal threaded pipe joints.
• Prevents leakage of water, air, gas in fittings.
• Common in plumbing and gas fitting work.

5. Double-Sided Tape

• Adhesive on both sides, used for temporary or permanent bonding.
• Used in assembly of parts, labels, or holding small components.

6. Duct Tape

• Strong, fabric-based tape with water-resistant adhesive.
• Used for repair, binding, and sealing work.
• Useful in temporary fitting and field repair jobs.

Here is the answer to:

Q.4 (b) List and explain any five welding defects

Welding defects are imperfections or flaws that occur in a weld joint which may weaken the structure or affect its performance. These defects can be caused due to poor welding technique, incorrect materials, or environmental factors.

Five Common Welding Defects (with Explanation):

1. Porosity

• Caused by gas entrapment in the molten weld pool.
• Appears as small holes or cavities in the weld.
• Reduces the strength and appearance of the weld.
• Caused due to moisture, dirty base metal, or improper shielding gas.

2. Cracks

• A serious defect that can occur during or after welding.
• Types: Hot cracks, cold cracks, or crater cracks.
• Caused by rapid cooling, high residual stress, or brittle material.
• It can lead to failure of the welded joint.

3. Incomplete Penetration

• The weld metal does not fully penetrate the thickness of the joint.
• Leaves a weak spot in the weld.
• Happens due to low current, incorrect joint design, or improper technique.

4. Undercut

• A groove formed at the base metal along the edge of the weld.
• Reduces cross-sectional thickness, making the joint weak.
• Caused by excess heat, high welding speed, or wrong angle of electrode.

5. Slag Inclusion

• Non-metallic slag particles get trapped in the weld.
• Occurs when slag from previous weld pass is not cleaned properly.
• Weakens the joint and may lead to crack propagation.

Plastic moulding is a process used to shape plastic into usable products by applying heat and pressure. It involves placing plastic material into a mould where it takes the shape of the mould cavity after cooling.

The main techniques of plastic moulding are:

1. Injection Moulding

• Plastic granules are melted and injected into a closed mould under high pressure.
• After cooling, the mould opens, and the solid product is ejected.
• Best for making high-volume products like bottle caps, toys, and containers.

2. Blow Moulding

• A hollow plastic tube (parison) is inflated inside a mould using compressed air.
• The plastic expands and takes the shape of the mould.
• Common for producing plastic bottles and hollow parts.

3. Compression Moulding

• Heated plastic is placed in an open mould.
• The mould is then closed and compressed, forcing the material to flow and fill the cavity.
• Used for making electrical fittings, switches, and trays.

4. Rotational Moulding

• Plastic powder is placed inside a hollow mould.
• The mould is heated and rotated slowly, causing the plastic to stick to the inner surface.
• Suitable for making large hollow products like tanks and bins.

5. Thermoforming

• A plastic sheet is heated until soft and then shaped over a mould using vacuum or pressure.
• After forming, the excess material is trimmed.
• Used for packaging trays, disposable cups, etc.

Arc welding is a fusion welding process where heat is produced by an electric arc formed between an electrode and the base metal. This heat melts the metal and electrode, forming a joint when it solidifies.

Working Principle of Arc Welding

• An electric arc is produced between the electrode and the workpiece using an AC or DC power supply
• The arc generates intense heat (around 6000°C)
• This heat melts both the base metal and the tip of the electrode
• The molten metal fills the gap between the workpieces
• The flux coating on the electrode melts and forms a protective gas shield and slag
• This shield protects the molten metal from oxidation

Types of Arc Welding

• Manual Metal Arc Welding (MMAW) or Shielded Metal Arc Welding (SMAW)
• Gas Metal Arc Welding (GMAW) or MIG Welding
• Gas Tungsten Arc Welding (GTAW) or TIG Welding

Advantages

• Simple and low-cost process
• Suitable for outdoor and field work
• Produces strong and durable joints

Applications

• Used in fabrication of steel structures
• Widely applied in shipbuilding, automotive, construction, and pipeline welding

Post-processing means the steps done after 3D printing to improve the part’s look, strength, and accuracy. 3D printed parts often come out rough and may have extra materials that need to be cleaned or removed.

1. Removing Support Structures

• Some parts are printed with extra supports to hold them in place.
• These supports are removed using tools like cutters or machines.

2. Surface Finishing

• Printed parts can have lines or rough surfaces.
• We can smooth them by sanding, polishing, or blasting.

3. Heat Treatment

• Heating the part after printing helps remove stress and makes it stronger.
• Mostly done in metal 3D printing.

4. Machining

• To make holes or smooth edges more accurate, drilling or cutting is done.
• Helps in getting exact size and shape.

5. Infiltration

• Some parts are weak or have pores.
• A liquid (like resin or wax) is added to make it stronger.

6. Painting or Coating

• Paint or protective layer is applied for better appearance and safety from rust or sunlight.

7. Assembly

• If the product has many parts, they are joined together using glue, screws, or welding.

In casting process, while designing the pattern, we provide certain allowances to make sure that the final casting has the correct dimensions and quality. These allowances help to compensate for changes that occur during solidification and cooling.

Types of Casting Allowances:

1. Shrinkage Allowance

• Metal shrinks as it cools and solidifies.
• To compensate, the pattern is made slightly larger than the final part.
• Depends on the type of metal (e.g., cast iron shrinks less than steel).

2. Draft Allowance

• A small taper is given on vertical surfaces of the pattern.
• Helps in easy removal of the pattern from the mould without damaging it.
• Usually 1° to 3° taper is provided.

3. Machining Allowance

• Extra material is added to the casting where machining (finishing work) will be done.
• Ensures final dimensions are accurate after machining.
• More allowance is given for rougher surfaces.

4. Distortion Allowance

• Some shapes like U or L-shaped castings may bend or distort during cooling.
• The pattern is made in a modified shape to balance this distortion.

5. Rapping or Shaking Allowance

• When a pattern is removed from the mould, it is shaken or rapped.
• This can enlarge the mould cavity.
• So, the pattern is made slightly smaller to compensate.

Timber defects are imperfections that reduce the strength, durability, and appearance of wood. These defects occur due to natural growth conditions, seasoning problems, or poor handling.

Common Defects in Timber and Their Reasons:

1. Knots

• Dark, circular marks on the wood surface.
• Formed due to branches being enclosed in the growing tree.
• Reduce strength and make machining difficult.

2. Cracks (Splits and Checks)

• Openings along the grain of timber.
• Caused by uneven drying or shrinkage during seasoning.
• Can weaken the timber structure.

3. Shakes

• Separation between growth rings of the wood.
• Types: Heart shake, ring shake, star shake.
• Occur due to frost, wind, or improper seasoning.

4. Warping

• Twisting or bending of timber out of shape.
• Caused by uneven moisture loss during drying.
• Types: Bow, twist, cup, crook.

5. Sap Stains

• Discoloration caused by fungal attack in the sapwood.
• Happens when timber is stored in damp conditions.
• Affects appearance but not strength.

6. Borer Holes

• Tiny holes made by insects or larvae.
• Occur due to insect infestation after felling.
• Reduce strength and quality of timber.

7. Decay or Rot

• Caused by fungi in wet conditions.
• Makes timber soft and crumbly.
• Leads to complete damage if not treated.

Various Hand Tools Used in Forging:

1. Anvil

• A heavy iron block on which hot metal is placed and forged.

2. Hammer

• Used to strike and shape the heated metal (e.g., sledge hammer, ball-peen hammer).

3. Tongs

• Used to hold and carry the hot metal pieces during forging.

4. Swage

• A tool used for shaping metal, especially to make grooves or circular shapes.

5. Fuller

• Used to draw out metal or create grooves in the hot metal.

6. Chisel

• Used for cutting hot metal during forging.

7. Punch

• Used to make holes in the hot metal.

8. Hardie

• A chisel-type tool that fits into the anvil for cutting metal.

9. Flatter

• Used to flatten and smooth the metal surface.

Why Machine Forging is Better Than Hand Forging:

• Higher Precision: Machine forging gives better dimensional accuracy than manual forging.
• Increased Productivity: Machines can perform the work faster and for longer durations.
• Uniform Quality: Same amount of pressure and shape is applied every time, ensuring consistency.
• Less Physical Effort: Reduces labor fatigue and is suitable for mass production.
• Can Handle Complex Shapes: Hydraulic or mechanical presses can forge complex designs more easily.
• Better for Large Components: Machine forging is ideal for heavy and large-size forgings which are difficult to make by hand.

(a) Riser in Casting

• A riser is a reservoir of molten metal in the mould that supplies metal to the casting as it solidifies and shrinks.
• It helps to avoid cavities or shrinkage defects in the final casting.
• Risers are placed in the mould at points where shrinkage is most likely to occur.
• Types: Open riser, closed riser, blind riser, etc.

(b) Different Methods of Filing

Filing is the process of removing small amounts of material from a surface using a file tool.
Methods include:

1. Straight Filing – Long strokes along the full length, used for flat surfaces.
2. Cross Filing – Filing in a criss-cross pattern for fast material removal.
3. Draw Filing – The file is held sideways and drawn back and forth for smooth finishing.
4. Circular Filing – Used for filing curved surfaces or circular parts.
5. Pin Filing – Filing small, delicate components like pins or keyways.

(c) Difference between Electrode and Filler Rod

(d) Hot Rolling

• Hot rolling is a metal forming process where metal is rolled at a temperature above its recrystallization point.
• The metal is softened and easily shaped into desired forms using rollers.
• Used to make beams, rods, sheets, plates, etc.
• Advantages:
  • Reduces internal stress
  • Improves ductility
  • Cheaper and faster
• Disadvantages:
  • Rough surface finish
  • Less dimensional accuracy compared to cold rolling