CNC Machining Tools Overview

CNC Machining

CNC machining tools play a pivotal role in modern manufacturing, offering high precision, repeatability, and efficiency.These tools are controlled by computer programs that provide precise instructions for their movements and operations.
But have you ever thought about how much time you spend as a mechanical engineer or designer thinking about the machining of your parts? Do you, specifically, have understanding of the kinds of CNC machining tools needed to create different features or geometries?
Allow us to act as your tour guide as we introduce you to the most common equipment used in CNC machining.

CNC machining tools

The Significance of Tool Selection

You might wonder, does CNC machining tools selection truly matter? After all, there’s a multitude of CNC machining tools available, and one should be suitable for any job, right? Regrettably, that isn’t always the case. Certain geometries, such as fillets, necessitate careful tool selection. The radius of a fillet should be at least half the diameter of the end mill in use. Any smaller, and achieving the desired result becomes more challenging, potentially requiring an unnecessary tool change.

When designing features for your part, it’s prudent to ensure they can be machined using standard tool sizes. For instance, if you include drilled holes, it’s advisable to align them with commonly available drill bit sizes rather than deviating by a millimeter. Where possible, opt for standardized features, maintaining consistency in hole sizes whenever feasible.

Familiarizing yourself with commonly available CNC milling tools can also simplify the design process for machinability. Below is a list of frequently accessible CNC milling tools that most machine shops typically possess. Should your design necessitate a unique tool, the machine shop may incur additional time and costs to source a custom solution.

Commonly Used Machining Tools

Face Mill/Shell Mill

A face mill or shell mill typically serves as the inaugural tool in CNC machining operations. These tools typically possess diameters ranging from a few inches and excel at material removal across broad areas. They are invaluable for the initial roughing pass to level the surface of your stock material, providing a uniformly even surface for subsequent machining.

Square End Mill

The square end mill is a quintessential tool found in every machine shop, available in multiple sizes. Its versatility allows for both bottom and side cutting, making it suitable for tasks like facing the top and sides of a part or hollowing out cavities.

Bullnose End Mill

Closely resembling the square end mill, the bullnose end mill features a slightly rounded bottom edge. This imparts a filleted edge between the bottom of a pocket and the side wall, adding a refined touch to machining projects.

Ball End Mill

Distinguished by its fully rounded bottom, the ball end mill boasts a bottom surface diameter matching its tool size. It excels in surfacing operations such as 3D contours, leaving no sharp corners in its wake, unlike the square end mill.

Drill Bit

Drill bits are the go-to choice for creating holes in materials, serving various purposes like clearance holes, threaded holes, press fits, or locating points. Standard sizes exist for drill bits, and designing holes to align with these standard sizes simplifies the machining process. Consistency in hole size across your part can also reduce the need for unnecessary tool changes.


Tapping is the process of creating threaded holes, commonly used after drilling holes. There are two primary methods: cutting taps and forming taps. Both require pre-drilled holes. Cutting taps remove material from the hole to form threads, producing chips in the process. They are suitable for through holes where chips can exit. In contrast, forming taps do not remove material but reshape it to form threads. They require slightly larger pre-drilled holes and work best with certain materials like aluminum. Forming taps are ideal for blind holes as they do not generate chips, resulting in cleaner holes and stronger threads.

Chamfer Mill

Chamfer mills, as the name implies, create external chamfers on sharp corners and can also machine countersinks. They are available with standard angles of 30, 45, and 60 degrees. Choosing one of these standard angles can simplify the design process.

Keyseat Cutter

Keyseat cutters facilitate machining undercuts or T-slots within the existing setup, eliminating the need for additional orientations. They can pass entirely through a part for T-slot machining or run along the side to create one-sided undercuts. Keyseat cutters come in straight-edge or radiused-corner varieties to produce rounded undercuts.

Slitting Saw

A slitting saw, resembling a thin keyseat cutter with a wider cutting surface radius, excels at cutting deep slots and even splitting parts. These versatile tools find diverse applications in machining projects.

Less Common CNC Machining Tools

The aforementioned CNC machining tools possess broad applications and are readily available across the industry. However, there exists a plethora of specialized CNC machining tools designed for more specific purposes. If you can envision it, chances are there’s a tool tailored for the task. The following CNC machining tools, while less commonplace, still offer valuable utility.


Reamers do not create holes but excel at enlarging existing ones to the precise diameter required. They yield a fine surface finish and maintain tighter tolerances compared to drill bits.

Fly Cutters

Similar in function to a face mill, fly cutters feature a single cutting surface mounted on a bar. This bar can be adjusted within the tool to achieve varying cutting diameters.

External Radius Cutter

External radius cutters are specialized tools designed to introduce a radius to external edges, such as those around the rim of a pocket.

Engraving Tool

Engraving tools are ideal for inscribing text or outlining shapes on a part’s surface.

Countersink Tool

Countersink tools create countersinks in drilled holes, also serving the purpose of cutting chamfers.

Dovetail Tool

Dovetail tools are used to cut a specific type of undercut into the material, known as a dovetail, adding a unique feature to your machining projects.

CNC Machining Tools at Sungplastic

We will select CNC machining tools for operation and production as your specialized engineer. However, you can consider your part’s design carefully to minimize the variety of CNC machining tools utilized and make sure the necessary equipment are common and readily available at most machine shops.
Choosing the right CNC machining tools is only one aspect of Design for Manufacturability. Consult our DFM for CNC Machining to find out other strategies for reducing production effort in your designs.

We can support metal and plastic CNC machined parts manufacturing, please contact us for specific projects!

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