Plain Milling: Process, Applications, and Advantages

In today’s world, product design requirements have become more and more demanding. Therefore, manufacturers leverage different machining processes to produce the desired goods and meet consumer demand. One such machining process used to produce goods across industries is plain milling.

So, what exactly is plain milling? How is it performed and what are the benefits of this process? In this article, I’ll answer all your burning questions and discuss everything you need to know about plain milling. Let’s dive in!

What Is Plain Milling?

Plain Milling

Plain milling, also known as slab or surface milling, is a process used when machining a flat, horizontal surface. It involves using a milling cutter which rotates on an axis that is parallel to the milled surface. The movement of the cutter removes unwanted material from the workpiece creating the desired end product.

How Does This Machining Process Work?

The plain milling process involves the following steps.

Choosing a suitable tool

The first step in the plain milling process is choosing a suitable milling cutter. Heavy-duty cutters are perfect for substantial material removal while light-duty cutters remove a small quantity of material. Also, light-duty cutters operate at a lower table speed and high tool speed and vice versa. Once you’ve selected the appropriate cutter, it is fitted on the milling machine spindle.

Workpiece setup

Next, the workpiece is secured on the milling machine. This can be done using a universal vise or an adjustable angle plate. Correct positioning of the workpiece allows for precision and accuracy in the milling process.

Cutting parameters

The quality of the end product depends on several factors namely spindle speed, milling feed rate, and depth of the cut. Suitable cutting parameters will depend on the workpiece material, tool capabilities, and desired finish.


If the cutter is rotating too fast, it may get destroyed or produce a rough surface finish. On the other hand, slow cutting speeds may mean an inefficient machining process.

Milling feed rate (Table feed)

The feed rate refers to the velocity at which the cutter advances against the material. The tool must advance at the right pace to generate consistent and precise cuts.

The depth of the cut

Refers to how deep the tool is pushed into the workpiece with each pass. This parameter affects the performance and efficiency of the machining operation.

Milling operation

Once the milling machine gets going, the cutter will rotate at a specific speed known as the spindle speed. The plain milling cutter removes material from the workpiece producing precise shapes and dimensions of final products. Depending on the orientation of the tool, milling machines are classified into vertical and horizontal milling machines. In a horizontal milling machine, the spindle is parallel to the worktable. Conversely, a vertical mill has a spindle that is perpendicular to the table.

What Are a Plain Milling Cutter

Plain milling cutters are available in different shapes and sizes, each suitable for a specific purpose. A plain milling cutter will typically have a cylindrical shape with cutting teeth on the periphery.

Plain milling cutters are grouped into two major categories;

  1. Light-duty plain milling cutters

  2. Heavy-duty plain milling cutters

Let’s take a closer look at the different types of cutters.

Heavy-Duty Plain Milling Cutters

As the name suggests, heavy-duty cutters are suited to heavy-duty milling operations. They are the ideal choice when working with complex materials that require higher cutting forces. This cutting tool is characterized by fewer helical teeth which generate a coarse cut and remove a larger amount of material.

Due to the roughness of the cut, heavy-duty cutters are more suited to rough cuts rather than finishing operations. The number of helical flutes also determines the feed rate. Due to fewer teeth in this machine tool, it operates at a high feed rate and low spindle speed.

Heavy-duty cutters are commonly used in the aerospace and automotive industries to manufacture large, robust components.

Light-Duty Plain Milling Cutters

On the contrary, light-duty cutters are designed for less intensive milling work. They have more cutting teeth and can perform delicate tasks leaving a fine surface finish. Due to the higher number of cutter teeth, these tools operate at a higher spindle speed and lower feed rate.

Light-duty cutters are known for their versatility. They are perfect for creating detailed designs, working on smaller operations, and even milling softer materials.

Choosing a Plain Milling Cutter

So, is it to choose the right plain milling cutter? The simple answer is yes. Your chosen cutter will affect the efficiency of the milling operation as well as the quality of the finished products or parts.

The choice between light-duty cutters and heavy-duty cutters depends on the specific plain milling job. Heavy-duty milling cutters have fewer teeth and are ideal for removing a large amount of material. They are suitable for cutting operations where the workpiece’s surface finish is not a primary concern. Conversely, light-duty cutters are appropriate for removing small quantities of material and milling operations that prioritize a fine surface finish.

The plain milling cutter material is also an important factor to consider. High-speed steel tools are a cost-effective option that is less susceptible to tool wear. Cutting tools made from rigid materials, such as cemented carbides and cutting ceramic, are perfect for high-performance plain milling operations.

Applications of Plain Milling

Plain milling can remove a large or small amount of material to produce parts of varying sizes. Manufacturers apply this technique when creating level faces or shaping workpieces.

This machining process has a range of applications in the automotive, aerospace, medical, defense, construction, and other manufacturing industries.

What Are of the Materials Suited for Plain Milling?

Plain milling is a versatile process that is compatible with a range of materials. It is commonly used for metals such as steel, titanium, aluminum, cast iron, and copper.

The machining operations are typically adjusted depending on the material being milled. For example, titanium milling requires carbide-cutting tools as they are more durable and heat-resistant. Similarly, softer metals can be milled using carbon steel cutters.

Besides metals, surface milling can be used for non-metals such as polyvinyl chloride (PVC), nylon, acetal, carbon fiber, and high-density polyethylene (HDPE).

Tips for Slab Milling

Face Milling

Plain milling is a relatively straightforward process. That being said, machinists need to observe the following guidelines to ensure high-quality milled parts.

  • A common issue that may arise during slab milling is vibration. By maintaining enough clearance between the spindle and the cutter, machinists can decrease the vibration tendencies.

  • CNC machines are known for their precise and efficient capabilities. This technology automates the movement of the machine tool creating accurate, high precision parts.

  • Before you start the surface milling process, choose a suitable plain milling cutter material and cutting speed for the operation. Carbide tooling is typically used for high-speed milling while carbon steel tooling is common in low-speed milling.

  • During plain milling, use lubricants or coolants, especially during surface finishing processes. This improves chip control and promotes a higher-quality surface finish.

Advantages of Plain Milling

Plain milling offers numerous benefits over other operations. These include;

High precision machining

Plain milling is an excellent choice for precision machining. It can achieve tight tolerances making it a go-to process for operations that call for exact measurements. This degree of accuracy is necessary in industries like aerospace and automotive where even minor errors can have a significant impact.

Compatibility with CNC technology

Computer numerical control (CNC) technology can be incorporated into plain milling resulting in a precise and automated operation.

Fabricators prefer CNC milling machines as they offer advanced accuracy, speed, and a high level of repeatability compared to manual machines. Further, the digital process is capable of manufacturing complex parts with minimal human involvement.

Lower labor requirements.

Manual milling heavily relies on human effort to produce products and parts. Adopting CNC technology has the added benefit of reducing the manual labor required. This means a faster machining process and a lower risk of human error. Also, the machine shop may save on labor costs.

Plain milling is a versatile process

Plain milling is compatible with a variety of materials ranging from metals to plastics. It is also capable of machining different shapes and sizes. Whether you’re machining a flat surface or a complex geometric shape you can employ this technique.

Owing to this versatility, plain milling is used in different fields ranging from electronics to medical equipment to consumer goods.

Fine surface finish

Plain milling is capable of generating an exceptionally smooth surface finish, which plays both an aesthetic and functional purpose. Therefore, plain milling operations are utilized in the manufacture of consumer goods and medical equipment.


Another advantage of plain milling is its cost-efficiency. This production process produces minimal waste, saves time, and lowers production costs. This cost-effectiveness is particularly beneficial during mass production where even small savings can quickly add up.

Comparing plain milling with other milling processes

Plain milling is a popular machining technique used in manufacturing both metal and non-metal parts. Besides slab milling, other milling processes also use rotary cutters to remove material from a workpiece. Understanding the different milling operations is crucial when choosing a suitable process for a specific project.

Plain Milling vs Face Milling

As we’ve already discussed, plain milling is used in machining a flat surface parallel to the cutting tool axis. Contrarily, in face milling, the flat surface is perpendicular to the spinning axis of the cutting tool.

Due to this orientation, plain milling allows for more of the cutting edge to be in contact with the workpiece surface. Therefore, this technique is suitable for removing a large amount of material while face milling is ideal for fine surface finishes.

Plain Milling vs Slot Milling

As the name suggests, slot milling is a process used in creating slots in workpieces. These slots come in different shapes and sizes and this determines the proper milling cutters. For example, T-slots and dovetail slots will have different tooling requirements.

The main difference between slot and slab milling is that the latter focuses on flat surfaces while the former is specific to different types of slots and grooves.

Plain Milling vs Form Milling

Form milling is a machining process that involves creating irregular contours using formed milling cutters. These contours may consist entirely of curves or both curves and straight lines. Unlike plain milling which is all about flat surfaces, form milling caters to unique designs and contoured shapes. Also, form milling cutters are typically 20 to 30% slower than surface milling cutters.

Plain Milling vs End Milling

End milling is a specialized milling technique in which the cutter has cutting edges on both its periphery and tip. While plain milling is the go-to process for flat surfaces, end milling is used to machine features such as slots, grooves, profiles, contours, and mixed forms.

Plain Milling vs Gang Milling

Gang milling is a machining technique that uses two or more milling cutters simultaneously. Therefore, in a single pass, this process is capable of machining multiple surfaces of a workpiece. Gang milling utilizes a range of cutters including end mills, face mills, and even plain milling cutters.

With plain milling, a single cutting tool is used in machining a workpiece’s surface.


Plain milling is a popular machining technique that is suitable for flat surfaces. It is performed when the workpiece surface is parallel to the cutter’s rotation axis.

Plain milling processes can be performed using different types of tools. Selecting a suitable machine tool will not only boost efficiency but also lower costs and improve the quality of the end product.

Advancements in technology have revolutionized how manufacturers approach the plain milling process. Using CNC mills, machinists can achieve exceptional speed, precision, and quality.

To sum it up, the key to successful plain milling operations lies in choosing the right milling cutter and cutting parameters depending on your project requirements.


Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.