Machining is a sector of the manufacturing industry that concerns itself with using machines to convert stock materials, such as steel and aluminum, into finished products. A sector is a portion of an industry with distinct features or a unique purpose. The aviation sector has different machining demands than the agricultural sector. More on this later in the book.

Stock is the term used by machinists when referencing the beginning material’s size and composition before work has begun to form it into the finished product. Stock can be in bars, billets, castings, extrusions, forgings, or any form that can be held securely while being machined.

Bars can be round or rectangular in shape, with lengths of 10 feet to 20 feet. Bar stock requires cutting to predetermined sizes before the machining process can begin. The saw used to cut stock can be a CNC programmed saw, a band saw, or a chop saw.

A billet is a large piece of stock that does not need to be cut down before machining. Billet material usually arrives pre-cut on pallets, and the machinist transfers the stock from the pallet to the machine for processing.

Castings are created by pouring molten metal into a form and letting it cool and solidify. They are often made of cast iron, aluminum, or steel.

Forgings are parts which have been formed by extreme pressure sandwiching a hot piece of metal between two tool steel dies, giving it a specific shape, such as a mechanic’s wrench.

Extrusions are usually made of aluminum which has been heated and forced through a die, giving the stock its finished shape.

There are two basic types of machines used in the machining industry, the mill and the lathe. In general, a mill machines objects that are rectangular, a lathe machines objects that are round.

A milling machine holds the stock in a device such as a vise. The tool rotates and removes material from the stock. The table where the vise is bolted moves, which permits the cutter to progress through a cut. All of these topics will be discussed in detail in further chapters.

On a lathe, the stock is held in a rotating vise called a chuck, and the tool is moved which results in material removal.

As a student in a machining program, you will become familiar with using both pieces of equipment to produce finished parts.

Image Placeholder: (image by Damon Donner) Alt text:

Advancements in technology have influenced the machining industry as they have in other industries. In the past, machining relied on subtractive machining techniques that would start with a large piece of stock material and remove material until the finished part was all that was left. Today, we also have additive manufacturing where parts are created by fusing powders in special machines one layer at a time. We call this technique additive manufacturing process printing. The advancements in 3D printing technologies are still in their infancy with a promising future in manufacturing.

Attributions

1. Figure 1.1: Aluminum bar stock arrives at an extrusion factory by Nicholas Malara, SBCTC Illustrator, for WA Open ProfTech, © SBCTC, CC BY 4.0
2. Figure 1.2: A brass casting machined by a lathe and a mill by Damon Donner, for WA Open ProfTech, © SBCTC, CC BY 4.0
3. Figure 1.3: A hot metal ingot loaded into a hammer forge by Rainer Halama is released under CC BY-SA 3.0
4. Figure 1.4: An assortment of extruded shapes made from aluminum by Nicholas Malara, for WA Open ProfTech, © SBCTC, CC BY 4.0
5. Figure 1.5: Round bar stock by Damon Donner, for WA Open ProfTech, © SBCTC, CC BY 4.0
6. Figure 1.6: A fly cutter in a manual mill by Damon Donner, for WA Open ProfTech, © SBCTC, CC BY 4.0
7. Figure 1.7: Robotics in the machining industry by Damon Donner, for WA Open ProfTech, © SBCTC, CC BY 4.0