Side Milling: Applications, Types, Tools Used, Advantages, and Disadvantages

Side milling is the process of machining the sides of a workpiece using a milling cutter. It is a common manufacturing process that is useful for creating slots, grooves, or complex geometries on the sides of a workpiece.

In this article, we explain what side milling is, how it is used, and its advantages and disadvantages. 

What Is Side Milling?

Side milling is a machining process that involves cutting or removing material from the side of a workpiece using a milling cutter. In side milling, the milling cutter has cutting edges (teeth) on the side as well as on the periphery. The cutter is mounted on an arbor, and the workpiece is secured on a milling machine table. The cutting tool, or in some cases the table, is then moved perpendicular to the workpiece’s surface to remove material from the workpiece. Side milling is compatible with a range of materials, such as: plastics, metals, and composites. This method is often used in the aerospace, manufacturing, and automotive industries. It is also commonly applied in conjunction with other machining methods such as turning, drilling, and boring, to create complex shapes in a workpiece.  

How Does Side Milling Differ From Other Milling Processes?

Side milling is a technique used to machine slots, simple contours, or the face of a workpiece perpendicular to the tool arbor axis. Side milling involves using a milling cutter to machine a workpiece from the side. The fact that the workpiece gets machined from the side makes it different from face milling, where the workpiece gets machined from the top. However, take note that, in side milling, as initially described, the milling cutter machines the workpiece from the side, creating slots, simple contours, or machining the face perpendicular to the tool arbor axis. This process is typically associated with a vertical tool axis. Now, if the tool axis is changed from vertical to horizontal, it would alter the machining dynamics and the orientation of the cut. In horizontal side milling, the cutter would engage with the workpiece from the side, but now the side is relative to a horizontal plane rather than a vertical one. The purpose of side milling is to machine slots, simple contours, or the face of a workpiece perpendicular to the tool arbor axis. This purpose differentiates it from processes such as thread milling, saw milling, profile milling, or slot milling, which are not used to create simple flat surfaces.

What Are the Key Applications of Side Milling in Manufacturing?

Side milling finds diverse applications across a range of industries. Some common applications of side milling include:

1. Flat Surface Machining: This milling technique is frequently used to create flat surfaces on workpieces, particularly on components that are too large for other machining processes like planing or grinding. This method can be used for manufacturing machine beds, tables, and bases. 
2. Slotting: Side milling is effective in creating grooves and slots on the sides of workpieces. This is used for the production of keyways, gears, and splines.
3. Contouring: Side milling is capable of creating complex contours and geometries on a workpiece. Specialized cutting tools with different profiles and shapes can be used to achieve precise dimensions and shapes in components. 
4. Surface Finishing: Achieving a smooth surface finish is a critical requirement in industries such as aerospace, where even minor imperfections can impact component performance. Side milling can be used to get a smooth surface finish. 

What Are Different Types of Side Milling?

There are two main types of side milling cutters, based on their primary design features:

1. Plain, or Straight-Tooth, Cutters: These cutters feature straight teeth that run parallel to the cutter axis. They are well suited for general-purpose milling and find application in machining flat surfaces and creating slots on workpieces. See Figure 1. 
2. Staggered-Tooth Cutters: Staggered-tooth side milling cutters have teeth arranged in a staggered pattern along the cutter circumference. This design helps to reduce vibration and chatter during the machining process, ultimately leading to a smoother surface finish. Staggered-tooth side milling cutters are commonly used in heavy-duty milling operations and are effective for machining uneven surfaces. Figure 1 below is an example of a staggered-tooth cutter:

What Materials Can Be Machined Using Side Milling Techniques?

Side milling can be used to mill: metals, plastics, and composites. 

What Tools and Equipment Are Required for Effective Side Milling?

Side milling requires specific tools and equipment to ensure precision, efficiency, and safety in the machining process. The essential tools and equipment for effective side milling include:

1. An appropriate side milling cutter is the primary tool for side milling operations. These cutters come in various types, such as plain or staggered-tooth designs, and are made from materials such as: high-speed steel, carbide, or ceramic. The choice depends on the specific application requirements.
2. A milling machine is a fundamental piece of required equipment for side milling operations. It provides the platform for securing the workpiece and the necessary movements to guide the side milling cutter. Both vertical and horizontal milling machines can be used for side milling, depending on the orientation of the machine you buy (horizontal or vertical).
3. The arbor is the component that holds the side milling cutter and connects it to the milling machine. An arbor support is used to stabilize and secure the arbor during the milling process, preventing excessive vibration and ensuring accuracy.
4. Various workholding devices are used, such as vises, clamps, or fixtures on a milling machine table, to secure the workpiece during side milling. These devices ensure that the workpiece remains stable and properly aligned throughout the machining operation.
5. Side milling generates heat due to friction between the cutter and the workpiece. A cutting fluid or coolant system is employed to dissipate this heat, lubricate the cutting tool, and flush away chips, promoting longer tool life and maintaining machining accuracy.

How Does Side Milling Affect the Surface Finish of a Workpiece?

Side milling generally produces a good surface finish with light to medium machining marks. However, the ultimate quality of the surface finish depends on a variety of factors that contribute to the roughness profile parameter, Rz (peak-to-valley average). A study entitled "Factors Analysis Affecting the Roughness at Side Milling" highlights the multifaceted nature of this process. Factors such as: cutting conditions, workpiece material, cutting geometry, tool errors, and machine tool deviations collectively impact the surface profile of milled parts. The analysis emphasizes that the surface roughness is not solely influenced by one factor, but rather by a combination of these elements.

Ultimately, whether the surface finish is good enough depends on the parameters of the side milling process and the application that the part is to be used for.

How Is Side Milling Different From Thread Milling in Terms of Procedure?

Side milling and thread milling are two different milling processes with different purposes and procedures. Side milling is primarily employed for surface machining, aiming to create flat surfaces or contours on the sides of a workpiece. In this process, a side milling cutter, mounted horizontally on an arbor, moves perpendicular to the workpiece surface, removing material from the side to achieve the desired flat vertical surfaces or contours. 

Thread milling, on the other hand, is used to cut threads, whether internal or external, on a workpiece. The procedure involves the use of a thread milling cutter with a unique design featuring multiple cutting edges. Unlike side milling, the thread milling cutter follows a helical path to gradually generate threads on the workpiece.

How Is Side Milling Different From Plain Milling in Terms of Procedure?

The primary distinction between side milling and plain milling lies in the orientation of the cutting tool and the resulting surface features. Side milling is used to make flat surfaces perpendicular to the cutter arbor axis, or to create slots, ledges, or other contours. In contrast, plain milling is focused on creating a flat, horizontal surface parallel to the axis of rotation of the milling cutter. The procedure utilizes a plain milling cutter, typically mounted on an arbor. The workpiece is secured on the milling machine table, and the cutter, aligned with the axis of rotation, removes material by rotating on its axis to produce a flat, horizontal surface. If you're using a narrow cutter, you can cut deeper into the material compared to using a wide cutter. The choice of cutter depends on the size and shape of what you're working on. If you have a big area to mill, a wide cutter is good because it means you need fewer passes. When you're removing a lot of metal, start with a rough cutter and then switch to a finer one for a smoother finish. For the initial rough cuts, it's better to go at a slower cutting speed with a fast table feed. When you're finishing up, speed up the cutting but slow down the table feed for a polished look.

What Are the Advantages of Side Milling in Industrial Production?

Side milling offers several advantages in industrial production settings, including:

1. Can be used to create various surface features, including: flat vertical surfaces, slots, and contours.
2. Is a good method for slotting and grooving operations. It is widely used in the production of: gears, keyways, splines, and other components 
3. Is useful in creating flat vertical surfaces. It is commonly used for machining components such as: machine beds, bases, and tables. 
4. Offers a wide selection of cutters in a range of sizes, types, and materials, providing flexibility in tool selection. 
5. Can achieve both high precision and accuracy.

What Are the Disadvantages of the Side Milling Process?

While side milling has several advantages, it also comes with certain disadvantages that should be considered. Among these are:

1. It is specifically designed for machining the sides of a workpiece.
2. Side milling is primarily focused on the production of external features, and it may not be the best choice for machining internal features or cavities within a workpiece. Other processes, such as end milling or drilling, may be better suited for such tasks.
3. May pose challenges when machining thin workpieces due to the potential for deflection or bending.

What Factors Influence the Quality and Precision of Side Milling Operations?

There are quite a few factors that can influence the quality and precision of side milling. Some of these include:

1. The feed rate of the machine and the depth of the cut.
2. The tool design (e.g. the number of teeth, wear resistance of tool, helix angle, and rake angle, influences the cutting forces, chip formation, and overall performance during side milling).
3. The material composition of the cutting tool. 
4. The accuracy and alignment of the milling machine's spindle.
5. The stiffness of the tool.
6. The hardness of the workpiece material affects tool wear and the forces exerted during cutting. Softer materials may require different cutting parameters than harder ones.
7. The speed at which the cutting tool moves through the workpiece affects tool life, chip formation, and the quality of the machined surface. 
8. The skill and expertise of the machine operator.

To get the best results, it is crucial to understand these factors and implement measures to reduce their influence.

How Does the Choice of Cutting Tool Material Impact Side Milling?

The choice of cutting tool material in side the milling process impacts: tool performance, tool life, machining efficiency, and product impact. Different tool materials are chosen to maximize performance under specific sets of machining conditions. For example, plain carbon tool steel maintains a cutting edge due to its high abrasion resistance but loses hardness above 250 °C. It is an appropriate choice for low-speed machining of materials such as aluminum and magnesium.

Harder materials like carbide offer greater durability and wear resistance, enhancing tool life and maintaining cutting performance during side milling operations. These tools remain hard even at temperatures up to 1000 °C. They are also able to withstand high-speed cutting operations.

Can Side Milling Be Used To Create Complex Shapes and Profiles?

Yes, side milling can be used to create complex shapes and profiles. This is achieved through the use of specialized cutters to create contours and complex profiles.

What Safety Precautions Should Be Taken During Side Milling?

During side milling, adhere to these safety precautions:

1. Wear appropriate personal protective equipment (PPE), including safety glasses, hearing protection, and work gloves, to safeguard against potential hazards.
2. Ensure that the milling machine is equipped with proper guards to prevent contact with moving parts, reducing the risk of injuries.
3. Properly secure the workpiece to prevent unexpected movement during milling.
4. Regularly inspect and maintain milling tools to ensure that they are in good condition, minimizing the risk of tool failure during operation.
5. Provide training for operators on the safe use of milling machines, including: proper tool handling, machine operation, and emergency procedures.
6. Familiarize operators with the location and use of emergency stop buttons to quickly halt machine operations in case of any unforeseen issues.

How Do You Calculate the Correct Feed and Speed for Side Milling?

The correct feed and speed for side milling can be calculated using the following equations:

RPM = (12 Surface Speed) / (PI Tool Diameter) [revs/min]

Feed Rate = RPM Chip Load Number of Teeth (Flutes) [in/min]

Where PI is a constant (3.14159).

What Are the Common Challenges and Solutions in Side Milling?

Below are some common problems associated with side milling and ways to improve them:

1. Effective chip evacuation is crucial to prevent recutting, heat buildup, and tool damage. Choosing side milling cutters with specialized chip breakers can significantly improve the chip removal process. Additionally, adjusting feed rates and ensuring proper coolant flow contribute to smoother chip evacuation, leading to improved surface finish and prolonged tool life.
2. Excessive vibration and chatter can adversely affect surface quality and tool life. To mitigate these problems, it is recommended to reduce radial engagement and utilize shorter tool holders for increased rigidity. Opting for side milling tools with built-in vibration-dampening features further enhances stability during the cutting process, resulting in improved machining performance.
3. Premature tool wear is a common challenge that can impact the cost-effectiveness of side milling operations. The selection of high-quality side milling cutters with advanced tool coatings is essential to address this. Optimizing cutting parameters, such as tool speed and feed rate, plays a key role in prolonging tool life and minimizing the need for frequent replacements.
4. Tool breakage during side milling can lead to downtime and increased operational costs. To prevent this, it is advisable to reduce feed rates (still within the calculated range) and use shorter tools for cases in which end mills are used, minimizing the risk of tool breakage. Additionally, ensuring proper tool alignment and a secure tool setup contribute to enhanced tool stability, reducing the likelihood of breakage.
5. It’s important to select the right side milling tools with appropriate coatings and materials tailored for specific workpiece materials. This can enhance tool life and overall machining efficiency.
6. Machining thin-walled components by side milling presents challenges due to the risk of workpiece deformation. Preventive measures include utilizing extended-length end mills with specialized geometries to reduce cutting forces on thin-walled components. Additionally, decreasing feed rates and providing additional workpiece support help minimize deflection.

How Has Technological Advancement Improved Side Milling Techniques?

There have been a few advancements in milling as a whole, which are not necessarily just applicable to side milling. Some of these technological advancements include:

1. Chip Slitter End Mills For Deep Cavity Machining: Cutting-edge chip splitter technology incorporates strategically placed chip gashes along the flute of end mills. These chip splitters effectively split chips in half, facilitating the efficient clearance of material and ensuring clean cuts. This innovative solution not only prevents bird nesting but also significantly reduces the risk of tool breakage. End mills equipped with this design excel in various machining applications, including: deep cavities, side milling, shoulder milling, and helical milling. The active control over chip size makes these cutting tools particularly well-suited for mold builders seeking optimal performance and reliability.
2. CNC Machining: Computer numerical control (CNC) technology has revolutionized milling processes, including side milling. CNC machines allow for precise control over tool paths, speeds, and feeds. This results in higher accuracy and repeatability in side milling operations. CNC milling technology has undergone remarkable advancements, with five key developments standing out. Firstly, there's a significant boost in processing power, enabling faster and more precise machining cycles. Advanced controls offer greater flexibility and improved user interfaces. Precision has increased through enhancements in machine components. Multi-axis capabilities, especially 4 and 5-axis milling, have become more common, allowing for more complex machining in a single setup. Lastly, automation integration is now feasible, leading to improved productivity and the potential for unattended operation.
3. Micromilling: Micromilling is a specialized milling technique that makes use of small-diameter cutting tools to achieve unparalleled precision on a miniature scale. The use of sub-millimeter end mills enables the creation of intricate features and fine surface finishes. Micromilling is particularly valuable in industries requiring precision at small scales, such as: electronics, medical devices, and aerospace. This technique brings a new level of detail to side milling applications, allowing for the machining of tiny slots, grooves, and features with high accuracy. 
4. IoT Integration for Smart Milling: A noteworthy recent advancement in milling applications is the integration of the Internet of Things (IoT) technology. IoT brings a new dimension to milling processes by facilitating connectivity and data exchange between CNC milling machines and various sensors, devices, and computer systems. This interconnected ecosystem enables real-time monitoring, analysis, and optimization of milling operations. Through sensors embedded in the milling equipment, data on factors such as temperature, vibration, tool condition, and machine status are continuously collected. This data is then transmitted and analyzed, allowing operators and manufacturers to make informed decisions for process optimization and predictive maintenance. IoT integration in milling applications enhances overall efficiency, reduces downtime, and contributes to the development of smart, adaptive machining systems.

What Are Ways Can Side Milling Be Integrated With CNC Technology?

Integrating side milling with CNC (Computer Numerical Control) technology offers a streamlined and precise approach to machining operations. CNC technology allows for the automation of side milling processes by programming the CNC machine to follow specific toolpaths and parameters. This integration eliminates the variability associated with manual operation. CNC systems provide unparalleled control over cutting speeds, feed rates, and tool movements, ensuring accuracy and repeatability in milling tasks. 

Is Side Milling a Common Manufacturing Process?

Yes, side milling is a fairly common manufacturing process that is used whenever the side of a workpiece needs to be machined to have flat or contoured surfaces or it can be used for other specific features like slots and grooves.

What Is the Difference Between Side Milling and Saw Milling?

Side milling and saw milling differ in purpose and in the type of cutting tool used to perform the two operations. Side milling is a machining process where milling cutters are used to create flat surfaces or slots on the side of a workpiece. Saw milling is a machining process where a thin cutting tool, known as a slitting tool, is used to cut narrow slots in a workpiece or part a workpiece in two. 

Summary

This article presented side milling, explained it, and discussed its various applications and types. To learn more about side milling, contact a Xometry representative.

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