What are the differences between those metal joining methods: 1) mechanical fasteners, 2) soldering, 3) brazing, 4) welding.

1) Mechanical fasteners: These are devices such as screws, bolts, nuts, rivets, and pins that are used to join two or more pieces of metal together. They rely on friction or tension to hold the pieces in place and can be easily removed or adjusted if necessary.

2) Soldering: Soldering is a process in which a filler metal (solder) is melted and flowed into the joint between two metal pieces. The solder forms a bond with the metal surfaces, creating a strong and permanent connection. Soldering is typically used for joining smaller, more delicate metal pieces.

3) Brazing: Brazing is similar to soldering, but it involves melting a filler metal with a higher melting point than solder. The filler metal is heated above 450°C (842°F) and flows into the joint between the metal pieces. Brazing creates a stronger bond than soldering and is often used for joining larger or more structurally demanding metal pieces.

4) Welding: Welding is a process in which two metal pieces are joined together by melting the base metal and adding a filler material (if necessary) to create a strong bond. Welding requires high temperatures and specialized equipment, such as a welding machine or torch. Welding produces a permanent and very strong joint, making it ideal for joining thick or heavy metal pieces.

1. Mechanical Fasteners

- Mechanism: Use nuts, bolts, screws, or rivets to physically hold metal pieces together.
- Advantage:
- No heat required, so no distortion or weakening of the metal.
- Easy to disassemble and reassemble.
- Disadvantage:
- Requires holes in the metal, which can weaken it.
- Can produce vibration and noise.

2. Soldering

- Mechanism: Uses a low-melting point metal alloy (solder) that melts and flows between metal surfaces, creating a strong bond.
- Advantage:
- Relatively low temperature, so minimal distortion or weakening of the metal.
- Can join dissimilar metals.
- Disadvantage:
- Strength is generally lower than other methods.
- May require flux to prevent oxidation.

3. Brazing

- Mechanism: Similar to soldering, but uses a higher-melting point metal alloy (brazing filler metal).
- Advantage:
- Stronger bonds than soldering.
- Can withstand higher temperatures.
- Disadvantage:
- Higher temperatures may distort or weaken the metal.
- Can require flux and shielding gas.

4. Welding

- Mechanism: Involves melting the edges of metal pieces together using an electric arc or flame.
- Advantage:
- Creates highly durable, permanent joints.
- Can join thick or complex shapes.
- Disadvantage:
- Requires high temperatures, which can distort or weaken the metal.
- Can pose safety hazards due to sparks and fumes.

Summary Table:

| Method | Mechanism | Advantages | Disadvantages |
|---|---|---|---|
| Mechanical Fasteners | Nuts, bolts, screws, rivets | Easy to disassemble, no heat | Holes weaken metal, vibration |
| Soldering | Low-melting point metal alloy | Low temperature, dissimilar metals | Lower strength |
| Brazing | Higher-melting point metal alloy | Stronger bonds, higher temperature | Distortion, flux required |
| Welding | Melting metal edges together | Durable joints, thick shapes | High temperature, safety hazards |