Skip to content 
What Is Side Milling?
Side milling is a common technique that involves using different CNC milling tools with teeth on the periphery or side to create keyways, slots, and other features on the sides of a workpiece, whether on a horizontal or vertical plane. The cutter moves perpendicularly to the workpiece’s surface to remove material from its side. Side milling’s versatility allows it to work well with various materials, including plastics, metals, and composites. It provides reliable results in milling different automotive, aerospace, electronics, and medical components.
Machinists often utilize side milling with other machining processes like turning, boring, and drilling to create complex geometries on a workpiece. A side milling cutter is the designated machine tool for side milling operations. It is cylindrical with cutting edges on its sides and allows the gradual removal of material from the workpieces. Side milling cutters come in varying sizes, from large cutters used for heavy-duty milling to small cutters used for precision milling tasks. Similarly, these CNC tools can be created from different materials, such as ceramic, high-speed steel, or carbide, depending on the specific application’s requirements.
How Does Side Milling Work?
In side milling, the cutter removes material on the workpiece’s side due to the cutter’s orientation. This marks the most critical distinction between this machining process and others, like face milling, which cuts from different axes or directions. The milling machine has a cutter attached to an arbor responsible for slicing the material clamped down to the work table.
The cutting tool’s edges are cut into the raw material to create a preferred shape or design. Here are standard formulas engineers rely on to get the right feed rate for side milling:
To calculate the right RPM, use RPM = (12 Surface Speed) / (Pi Tool Diameter) [revs/min]
For the right feed rate, use Feed Rate = RPM Chip Load Number of Teeth (Flutes) [in/min]
Note, Pi = 3.14159
When to Consider Side Milling for Your Project
Side milling is undeniably a fundamental process with various applications across industries, offering a strategic approach for skilled operators in different scenarios. Knowing when to consider side milling helps achieve optimal machining results. In this section, we will explore scenarios where side milling is the perfect choice:
Slotting for Gears and More
Slotting is one of the principal applications of side milling. It is an effective means of making slots or grooves along the sides of workpieces. Machinists often employ this milling capability in producing gears, splines, and keyways. The ability of side milling machines to adapt to creating these essential features contributes to its excellence in gear manufacturing.
Machining Flat or Angled Surfaces
Most manufacturers leverage the versatility of side milling when making expansive flat surfaces on a workpiece, particularly when alternative processes like planning or grinding cannot accommodate the size of the workpiece.
Side milling is an invaluable approach for flattening down the surfaces of different components. The high precision of the side milling process guarantees desired flatness in critical components like engine and machine tool parts.
Surface Finishing Excellence
In the intricate world of milling, side milling contributes significantly to achieving superior surface finishes, especially in industries such as aerospace, where the performance of milled parts is closely associated with surface quality.
The side milling process ensures the milled parts are smooth. It refines surface finish to meet the strict requirements of different applications, such as aerospace, where the slightest defects can influence proper performance.
Contouring Complex Geometries
Side milling is a proficient contouring tool. It allows machinists to achieve intricate geometries and precise contours on a workpiece. Hence, manufacturers leverage specialized cutting tools with different shapes and profiles to create components with exact shapes and dimensions. Since side milling occurs on a horizontal milling machine, its nuanced control makes it valuable for applications requiring intricate and precise geometrical features.
Common Challenges of Side Milling and Helpful Ways of Overcoming Them
Side milling is not an entirely complex machining operation. However, things can get complicated, resulting in a few tricky challenges. Here are some of the common problems that happen in side milling:
Excessive Vibration and Chatter
Vibration and chatter occur in side milling due to tool deflection, unstable setups, high cutting forces, or wrong tool holding, resulting in poor surface finish, dimensional inaccuracies, and reduced tool life. AT Machining experts recommend using a lower radial engagement angle or shorter tool holders to prevent vibrations or chatter that can affect the surface finish and quality of milled parts.
You can perfect the surface finish of machined components through meticulous tool selection and optimization of machining parameters. Also, using tools with materials that match the specific workpiece’s requirements would help achieve the desired results.
Workpiece Deformation
Deformation is imminent when milling the side of an extremely thin or flexible workpiece under high thermal loads or cutting force—for instance, warping causes dimensional inaccuracies and poor quality in milled parts.
Hence, it would be best to use thicker diameters when side milling materials and reserve the thinnest workpieces for other machines if possible. As an alternative, experts advise slowing down the feed rate and ensuring the workpiece has ample support when milled.
Jerky or Inconsistent Chip Evacuation
Re-cutting of chips occurs due to poor chip evacuation, leading to tool damage and poor surface finish. Besides, jerky chip evacuation occurs when milling deep slots or sticky materials. To combat this, experts advise applying high-pressure coolants to aid in proper chip removal.
It is also advisable to purchase a side milling cutter with specialty chip breakers and monitor the coolant flow to achieve optimal chip evacuation. Furthermore, machining strategies such as trochoidal or helical tool paths should be employed to ensure smoother chip removal.
Tool Breakage
Machine tools can break due to improper machining conditions, high stresses, or extended use of cutting tools. Hence, ensure proper alignment, reduce feed rate, and use shorter cutters to avoid tool breakage in side milling. Adopting machining strategies like ramping is also advisable to reduce stress on the machine tool when milling the side of workpieces.
Premature or Rapid Tool Wear
Wrong feed rate and tool speed or lower-quality tools with shorter lifespans are often the leading causes of overtly quick tool wear during side milling. Although early wear detection is critical, it might help purchase high-quality cutters and machine components and adjust speeds and feeds according to the milled material.
Furthermore, you can increase the lifespan of your side milling tools through a comprehensive inspection routine that incorporates dimensional checks with regular visual examinations. Expert machinists recommend using advanced coatings such as titanium nitride to prolong tool life.
Side Milling vs. Plain Milling vs. End Milling: Exploring Their Differences
Side milling is a versatile process that excels in fabricating intricate grooves, shoulders, and other complex features such as contours along the side of components. Thanks to its varying cutter diameters and adaptable tooth arrangements, it provides remarkable adaptability in cutting deep slots and grooves.
Meanwhile, plain milling involves fabricating plane surfaces, particularly in scenarios where the productivity and accuracy of milled parts are crucial. The spiral or helical design of the cutter allows it to simultaneously engage the multiple teeth in the workpiece, ensuring a smooth operation with reduced vibrations and chatters. Plain milling can be categorized into conventional milling and climb milling. The rigid setup of the plain milling machine allows for optimal efficiency with a wider cutter.
In end milling the cutting tool rotates around its axis and moves axially along the workpiece’s surface to remove material from its end. End mills often come in different shapes and sizes, including corner rounding, ball nose, corner radius, tapered, square, and roughing end mills to meet the needs of various machining applications. These end mills have edges/teeth on the end of the cutting tool. Its design allows it to engrave the surface of the workpiece or male die cavities and machine different shapes and contours. However, the tool’s cutting-edge geometry often determines the machining operations that can be performed.
Best Practices to Ensure Successful Side Milling
Achieving precision in side milling requires meticulous attention to detail and careful consideration of different parameters. Various factors guiding side milling operations include:
Cutting Tool Selection and Materials for Side Milling
Ensuring the cutting tools and materials match every side milling operations can be tricky whether you are operating a milling machine for the first time or an expert. When using a horizontal mill, choose a cutting tool material such as carbide, diamond, or high-speed steel based on the requirements of the workpiece.
Similarly, customize the cutter’s design to ensure precision and fine details in milled parts. Customize the cutter geometry, number of teeth, and flute design to meet the workpiece-specific demands and intricacies of the milling task. Furthermore, explore coatings like titanium nitride (TiN) to enhance your cutting tools’ hardness and wear resistance, elevating longevity
Coolants and Lubricants for Side Milling
Coolants and lubricants are critical elements when operating a periphery milling machine. While lubricants help reduce friction, coolants ensure better heat dissipation during side milling. It is essential to monitor their presence and usage to ensure desired results.
An adequate supply of coolants to the cutting zone ensures the dissipation of generated heat from the cutting zone. Hence, it ensures the proper functioning of tools, avoids overheating, and guarantees efficient chip removal. Conversely, lubricants mitigate friction between the workpiece and the cutting tool. It ensures improved tool life and superior surface finishes on final products.
Technical Consideration for Side Milling
Various machine modifications like cutting speed and feed rate are essential to the success of side milling. Achieving the perfect balance between these parameters is an art. You may need to measure the tool’s edge movement through the material in SFM (Surface per minute) or MPM (meters per minute) to determine the ideal cutting speed.
Feed rate is another key technical aspect of side milling measured in millimeters per minute (MMPM) or inches per minute (IPM). You must define the speed at which the workpiece engages with the cutter.
Moreover, it is imperative to balance speed and feed to achieve efficiency in side milling tasks. Maintaining the right balance between feed rate and cutting speed is a technical requirement and key to mitigating tool wear while increasing productivity and achieving the necessary surface finish.
Safety Considerations for Side Milling
Here are helpful safety considerations to ensure your side milling operation is safe and efficient:
- Ensure each team member uses a side milling machine and that others around them can identify the emergency stop buttons and how to use them.
- Use personal protective equipment such as work gloves, safety glasses, and hearing protection, and ensure your milling machine operators or production team do the same.
- Train your team and ensure each personnel is up-to-date with the safety requirements.
- Use appropriate vises or clamps to secure the workpiece and avoid sliding, deviation, error, and hazards.
- Practice routine inspection of your side milling machines before using them, and ensure they are well-maintained.
- Ensures the milling machine guards are in place and work properly to prevent accidents or injuries common to moving parts.
Conclusion
Side milling provides the utmost precision and efficiency in machining complex and high-tolerance parts by allowing seamless material removal along the side of a workpiece. Understanding the principles, uses, and complexities of side milling is crucial to leveraging its benefits across industries.
AT-Machining is a top CNC machine shop that offers a variety of manufacturing capabilities applicable to the construction, aerospace, medical, and automotive industries. Our experts leverage our state-of-the-art CNC milling machines to meet the demands of your milled parts, whether prototypes, low-volume, or mass production. Submit your CAD file for a detailed and instant quote!
