Stecker Machine Blog

CNC Machining 101: Operator’s Guide to Milling Center Core Basics

02/19/2024 | Taylor Madden

CNC Vertical Machining Center Showing Several Major Components

Precision machining, particularly CNC (computer numerical control) machining, is vitally important in today’s economy, specifically for industries needing parts with unparalleled accuracy and complexity.

What industries? Aerospace, automotive, medical, defense, industrial machinery, electronics, and many more. Companies in these industries lean on CNC machining for its ability to produce high-precision components reliably and efficiently, which is crucial for their specialized applications.

CNC machines perform incredible tasks that efficiently produce intricate components, surpassing traditional machining methods in both precision and cost-effectiveness. In this article, we’ll take a high-level look at CNC machine parts and functions. The links you see will provide more details on that topic.

What is a CNC Machine?

A CNC machine utilizes computer programming to direct a machine’s tool functions and movements. These programs, either pre-written or auto-generated, contain coded programmed instructions (learn more about G-Code and M-Code here) that the CNC machine follows to execute the correct operations for part production.

The computer moves the tool or workpiece and controls the feed rate, cut depth, speed, and coolant flow. As the machine operates, it precisely removes material layer by layer to shape the workpiece. CNC machines can work on various materials, including metals, plastics, woods, and composites.

There are many different types of CNC machines, with each performing different functions. Standard CNC machining processes include these machining techniques:

  • Milling — A spinning cutting tool makes contact with a fixed workpiece
  • Turning — Spinning the workpiece while a cutting tool shapes it; typically done with lathes
  • Drilling — A rotating cutting tool cuts holes into a workpiece
  • Boring — Creating a precise internal cavity in a workpiece by material removal
  • Broaching — Sequential material removal with shallow cutting strokes
  • Sawing — Slicing a workpiece using the back-and-forth motion of a saw blade

Although the types of CNC machines vary quite a bit, no matter what the task, a CNC machine clearly excels in two ways: repeatability (the ability to make tens of thousands of identical parts) and precision (hitting position tolerances of +/- .001” or tighter).

RELATED: Learn the ins and outs of the industry! See our CNC Machining Guide.

What are the Parts of a CNC Machine?

Bed: Typically constructed from cast iron for enhanced durability and strength, the bed is the machine’s foundation, supporting all components.

Spindle: Inside the machining area, the electrically driven spindle rotates tools that cut and shape the parts. The inside of the spindle is tapered to match the tapered angle of the tool holder to maximize the surface contact that is required to hold the tool in place while cutting. A drawbar inside the spindle grips and pulls the retention knob on the tool holder to secure the tool in the spindle. The spindle on a horizontal machine holds the tool horizontally, and a vertical machine holds it vertically, thus the name for each.


Pallet: The pallet on a horizontal mill is used to mount the machining fixtures for particular parts to hold parts that are being machined. Fixtures firmly hold the part in an exact location and position. The pallets have aligning blocks on two sides that are used to locate the fixture into a location prior to being bolted in place. A horizontal machining center has two pallets. The operator can process parts on the pallet in the loading station while the second pallet is in the machining station having parts machined.

Control Panel: The control panel includes the input device, display unit, keyboard, and control buttons. Typically mounted on an extendable arm for easy positioning, it plays a crucial role in inputting programming instructions into the machine, complementing the machine control unit’s functions.

control panel

Display: Varying in size and resolution, this screen shows essential information for operator interaction: G-code, settings, and the machine’s operating status. By presenting programs, instructions, and real-time machine status, this unit ensures effective management and control of the CNC machine.

Machine Control: The MCU interprets G-code and handles operations such as task initiation, spindle speed, tool changes, and feed rate management. It translates G-code into instructions for tool drivers, coordinating servo motor movements across axes and ensuring tool accuracy with feedback sensors. 

Waycovers: The expanding and collapsing sheets of metal that cover the mechanism for moving the spindle or work table are called waycovers. Their purpose is to keep chips and other contaminants out of the precision machine parts that can be easily damaged if not properly lubricated and kept clean. It covers the ways and ball screws.

Waylube System: The waylube system lubricates the ways that the traversing table slides on and the ball screw that moves it.

Waylube Pump

Chip Conveyor: As a part is machined, metal chips are created, which can build up to interfere with tool, machine, or part movement and/or cause coolant to back up. The chip conveyor is a mechanism to remove chips from the machining area and segregate them from the coolant to assure proper coolant flow, which is critical to successful machining. It sends the chips to a dumpster and allows the clean coolant to flow back into the coolant tank.

Coolant System: To improve machining quality, a CNC machine uses coolant for numerous purposes, each with a separate coolant pump. A garden hose-type sprayer showers the machining with coolant, providing thorough spindle tool cooling while washing chips into the chip conveyor, and it directs a stream onto tools for lubrication.

Coolant Pump


Hydraulic System: Hydraulic pumps supply high pressure oil to lift the pallet, clamp the pallet, operate the draw bar, and clamp on a part holding fixture. There are separate pumps for each task, one for the machine and one for the fixture. The pump below is for machine functions, with a sight glass on the reservoir indicating the hydraulic oil’s current level.

Hydrolic Pump


Machine Tools: Machine tools perform tasks on workpieces, typically cutting. These tools vary across CNC types (lathes, mills, etc.) as mentioned above. Several cutting tools are held in the machine; 60 tool belts are common, and there are options to hold more or less tools. Tools are swapped automatically by a tool changer. Essential components like sliding tables, spindles, and their drives and motors are controlled via X, Y, and Z axes. For more details on how a CNC machine works (including 2-axis to 5-axis machines), review this article.

Driving System: Movement is controlled by electrical drives, servo motors, ball screws, and linear guides, ensuring exact precision. In a CNC mill, the pallet moves horizontally in the z-direction, and the cutting tool horizontally and vertically in x- and y-directions.

Footswitch or Pedal: CNC operators use foot pedals to open and close the chuck, allowing for easy loading and unloading of parts.

Additional CNC Machine Info a Beginner Should Know

World-class CNC machining isn’t just about the machine’s parts. CNC machines require proper maintenance to keep them running efficiently. See some tips here. Similarly, CNC machine cuting tools should be fully managed and available when needed.

Like many manufacturing disciplines, some myths give people the wrong impression about CNC machining. In reality, working environments are clean, worker safety is prioritized, new people are welcomed, and CNC machining is a solid career choice.

CNC machines use advanced technology to machine complex parts, yet it’s not extremely hard to learn and understand. In fact, many high school students and recent grads have jumped directly into a career in CNC machining. However, like with any trade, experience matters, and it generally takes two to three years of machining to become a proficient machine operater.

Lastly, working with an experienced, reliable CNC machine shop is a must, no matter what their size. This resource helps you determine if a high-end shop relationship is best for your manufacturing needs.

Now that you know about CNC machine parts and functions, explore our resource page that is dedicated to sharing CNC machining information, operator responsibilities, and industry trends: CNC Machining Guide. Click below for instant access.

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Taylor Madden

About the Author

Taylor serves as the Employee Development Manager at SMC, where he oversees training and safety initiatives. With a practical, hands-on approach, he tailors training programs to individuals, ensuring all new hires are properly trained for their roles. Taylor also spearheads the company's safety team, advocating for a culture of safety throughout the organization.