Metalworking

Metalworking is the way people shape and change metals to make useful things. It helps us make big things like ships, buildings, and bridges. It can also make small, precise engine parts and pretty jewellery.

People have been metalworking for a very long time, even before they could write. Many cultures and civilizations used metalworking to make tools, things to trade, art, and more. It started with shaping soft metals like gold by hand. Now, there are more complex ways to work with metal, like machining and welding.

Today, metalworking is done in special places called machine shops. These shops have many kinds of machine tools that help make accurate and useful products. Some older ways, like blacksmithing, are still used sometimes for special projects or as a fun hobby.

Prehistory

People have worked with metals for a very long time, even before we had written history. One of the oldest pieces of metal found is a copper pendant from northern Iraq, dating back to 8,700 BCE. In the Americas, people worked with copper around 4000–5000 BCE. They would hammer the copper until it became hard, then heat it to shape it again.

Gold is special because sometimes it can be found in nature as small pieces that need no special tools to shape. The oldest gold pieces ever found are from Bulgaria and are about 4450 BCE old. Most metals come from rocks called ores and need heat or other methods to get the metal out.

Over time, people learned to mix metals to make stronger ones. For example, mixing copper with tin created bronze, which was much stronger than copper alone and was used for tools and weapons. This time period is called the Bronze Age. Later, people began using iron, which led to the Iron Age. Different parts of the world, like China, Great Britain, and the Japanese islands, all developed these metalworking skills in their own ways.

History

See also: Ferrous metallurgy

Long ago, people in places like Egypt, India, North America, and many others began to value special metals such as gold and silver. These metals were used to create beautiful decorations, important religious items, and tools for trading. Skilled workers, like blacksmiths and metalsmiths, knew many clever ways to shape metals.

Over time, people discovered more uses for metals. They learned how to get metals from the earth and improved their skills in working with them. Metals became very important for making things like jewelry, electronics, buildings, ships, trains, and airplanes. Today, metals help us create and move many of the things we use every day.

General processes

Metalworking has three main types: forming, cutting, and joining. In cutting, special tools are used to shape the metal. Before starting, the metal is marked or measured to get the right size and shape.

Marking out, also called layout, is the first step. It means putting a design or pattern onto the metal. This helps prepare the metal for the next steps. Calipers are tools used to measure distances very precisely. Sometimes, a tape measure is used for bigger objects.

Casting

Main article: Metal casting

Casting is a way to make metal objects. You pour hot, liquid metal into a special shape called a mold. The metal cools down and hardens in that shape. No extra tools are needed to push or pull it. There are many kinds of casting, like investment casting (also called lost wax casting in art), centrifugal casting, die casting, sand casting, shell casting, and spin casting.

Forming processes

These forming processes change the shape of metal by pressing it without taking any pieces away. We use machines and sometimes heat to do this.

One type is called bulk forming. In this process, the metal is often heated before machines shape it. Examples include forging, rolling, and extrusion.

Another type is sheet forming. These processes shape thin pieces of metal using machines at normal temperatures. Some examples are bending, stamping, and coining.

Cutting processes

Main article: Cutting

Cutting is a way to shape metal by taking away extra pieces. This leaves a finished part that fits what we need. When we cut metal, we get two things: the waste pieces and the finished part. In woodworking, the waste is sawdust. In metal, the waste is small pieces called chips or swarf.

There are three main ways to cut metal:

• Chip producing processes, also called machining
• Burning, where we cut metal by heating it
• Special processes that don’t fit into the first two

For example, drilling a hole is a chip producing process. Using an oxy-fuel cutting torch to cut steel is burning. Chemical milling is a special process that uses chemicals to remove material.

We can cut metal in many ways, like using:

• Hand tools: saw, chisel, shear or snips
• Machine tools: turning, milling, drilling, grinding, sawing
• Burning tools: laser, oxy-fuel burning, and plasma
• Erosion tools: water jet, electric discharge, or abrasive flow machining
• Chemical tools: Photochemical machining

We use cutting fluid or coolant to keep tools and metal cool when there is a lot of heat and friction.

Milling

Main article: Milling (machining)

Milling shapes metal by taking away pieces to make the final shape. We usually do this on a milling machine. This machine has a milling cutter that spins, and a worktable that moves in different directions. The cutter can move up and down, and the table can move side to side.

Milling machines can make complex 3D shapes. They can cut slots, plane surfaces, drill and thread, and more. Some milling machines are controlled by computers, which helps make very exact shapes.

We use coolant to keep the cutter and metal cool. Safety is important because the cutter spins very fast.

Turning

Main article: Turning

Turning makes round shapes by spinning a piece of metal and cutting it with a tool. The tool moves into the spinning metal to make smooth, round surfaces.

A lathe is a machine that spins a piece of metal. It has a strong base, a part that holds the metal, and a tool that cuts the metal. Lathes can make many round objects, like candlestick holders and crankshafts.

Lathes have a base, a spinning part, a moving platform, and a tail part that can hold the metal or tools. Modern lathes can also do other tasks like milling with computer control.

Threading

Main article: Threading (manufacturing)

There are many ways to make threads, which are the spiral lines on screws. We can use a tap or die to cut threads, or use special machines to roll or grind them.

Grinding

Main article: Grinding (abrasive cutting)

Grinding uses a special wheel to remove tiny pieces of metal. This makes very smooth finishes or very precise shapes. The wheel can be made of different materials like stones, diamonds, or other hard substances.

Grinders can be small, like a hand tool, or very large for making jet engines. They need to be very strong to make exact shapes. Today, grinders can use computer controls for very precise work.

Filing

Main article: Filing (metalworking)

Filing uses a tool called a file to shape metal, like cutting with tiny teeth. It was used before modern machines to make small, exact parts. Today, it is mostly used to smooth edges.

Other

Broaching cuts grooves into shafts. Electron beam machining (EBM) uses fast electrons to heat and remove material. Ultrasonic machining uses vibrations to shape very hard materials.

Joining processes

Welding

Main article: Welding

Welding is a way to connect materials, usually metals, by melting them together and adding a special filler material. This creates a strong bond when it cools. Different energy sources like gas flames, electric arcs, lasers, and even friction can be used for welding. It can be done in many places, including underwater and in space. People need to be careful to avoid danger.

Brazing

Main article: Brazing

Brazing is another way to join metals. In this process, a special filler metal is melted and flows into the space between two metal pieces. The filler metal bonds with the pieces and hardens to make a strong joint. The metal pieces themselves stay solid. Brazing happens at higher temperatures than another method called soldering.

Soldering

Main article: Soldering

Soldering is similar to brazing but uses lower temperatures. A filler metal is melted and flows into the space between two pieces to create a bond. Because the temperature is lower, the bond is not as strong as with brazing or welding.

Riveting

Main article: Rivet

Riveting is an old method of joining metals. Though it is used less today, it is still important in some industries and crafts like making jewelry. A rivet is a special type of bolt with two heads that holds two pieces of metal together. Holes are made in the metal pieces, and the rivet is pushed through them. New heads are formed on the ends of the rivet to keep it in place.

Mechanical fixings

This includes screws and bolts. These are often used because they don’t need special tools. They are useful for joining metals to other materials like wood or metals that are hard to weld, such as aluminum. While these methods might not be as strong as welding, the metals can be taken apart and reused.

Associated processes

Metals can become stronger, more flexible, or better at resisting rust by using heat. Common ways to do this include annealing, which makes the metal softer; quenching, which makes some metals harder; and tempering, which helps the metal stay flexible after it is hardened. These steps help metals work better for different jobs.

Plating puts a thin layer of another metal, like gold or zinc, on the surface. This protects the metal or makes it look nicer. It can also change how the metal carries electricity or deals with heat.

Thermal spraying is another way to finish metals. It often gives better protection at high temperatures than plating. Different methods are used to put on the coating.