Milling is a common machining operation with many variations, making the choice of the right method a critical decision for machinists. Among these choices, face milling vs peripheral milling is one of the most fundamental comparisons – upon which all other types are based.
It is not that they are closely similar, but they often confuse beginners. Their cutting mechanisms are completely different. One cuts primarily with the tool’s end, while the other cuts with the tool’s sides. But is that information enough to decide which method to use? Probably not.
This guide compares both face and peripheral milling operations, their advantages, applications, limitations, and a few selection recommendations to help you choose between the two.
What is Face Milling?
Face milling is a machining process in which the cutting tool’s rotational axis is perpendicular (vertical) to the surface of the workpiece. The tool removes material using the cutting edges on the bottom face and outer edges of the cutter.
Usually, the entry angles for face mills are around 45° (balancing axial and radial forces). Special high-feed face mills use shallower angles (around 10–15°) to accommodate high feed rates.
Face milling is commonly used to machine and finish large flat surfaces (e.g., plates, bases, housings) and to establish a flat datum surface (Z=0) for further machining.
Working Process of Face Milling
In a face milling operation, the workpiece is clamped on the machine table, and the face mill is mounted in the spindle so its axis is vertical. The CNC machine is programmed so the cutter moves linearly along the surface.
As the tool advances along the surface, each insert on the cutter’s face engages and shears off a chip. Because the inserts are offset radially around the cutter, the material removal is spread over multiple edges, yielding efficient stock removal.
Cutting Tools for Face Milling
Face milling requires special cutters and corresponding face mill holders, which are chosen based on the part’s geometry and machining requirements.
Some common face milling tools include:
Shell (Face) Mills
Large-diameter cutters with multiple indexable inserts on the circumference and face. Shell mills are mounted on an arbor. The face mill arbor extension allows for covering wide areas and making deep cuts, which is why they’re standard for general flat-surface milling.
Fly Cutters
It’s a single-point cutter attached to an arbor (with just one insert). Fly cutters produce very smooth finishes on flat surfaces and are simple to set up, but are slower than multi-insert mills.
Comparing a fly cutter vs face mill, one is a single-point tool and has less rigidity, and another contains multiple inserts and is more rigid to support heavy machining tasks.
Indexable Face Mills
These tools involve strong face mill inserts with carbide or ceramic in a solid body. They offer high productivity and easy insert changes, great for high-volume production
Button Cutters (Round-Insert Face Mills)
These are specialized with round “button” inserts. These give a smooth cutting action on flat or slightly contoured surfaces and handle interrupted cuts well.
A bottom milling cutter for face milling can perform with distinct cutting angles for continuous roughing, semi-finishing, and profiling.
Advantages
Face milling offers several benefits:
- High Material Removal Rate (MRR)
- Smooth cutting provides an excellent surface finish.
- It excels at machining wide surfaces (e.g., plates, bases, mold faces) in fewer passes.
- Since cutting is shared among multiple edges, wear and tear are divided among inserts.
Disadvantages
There are a few limitations as well, like:
- Limited access to the tool
- No 3D contouring
- High Initial Tool Cost
Applications
Face milling is used whenever a flat surface needs to be produced. Common applications include:
- Surfacing/Leveling: Flattening the top face of a part or raw casting/forging.
- Squaring Ends: Cutting a square or flat end on a block or bar stock as a reference face before further machining.
- Finishing Large Faces: Achieving the final flatness and finish on machined plates, housings, or die components.
- Preparation for Further Ops: Facing a surface prior to drilling, pocket milling, or grinding to ensure a true datum surface.
Practical Tips and Recommendations for Face Milling
A practice, machinists recommend, is offsetting the cutter centerline from the part center during facing. This minimizes chip thickness at exit, reducing burrs and improving surface finish. It also helps avoid cutter dwell, which can cause vibration and insert damage.
Moreover, frequent entries and exits, especially over holes or slots, should be avoided. If unavoidable, reduce the feed rate during entry and exit to protect the cutting edge and limit stress buildup.
Apply coolant when machining hard alloys to flush chips and cool the insert edges. For materials that allow dry cutting (aluminum, plastics), coated carbide can help. Keep the work area clear of chips to avoid recutting.
What is Peripheral Milling in Machining?
Peripheral milling (or plain milling) is a machining operation where the cutter’s axis is parallel to the workpiece surface. The cutting action occurs along the circumference of the rotating tool.
Normally, an end mill on a vertical mill is used so that the flutes on the cutter cut along the length or periphery of the part. This method is designed for cutting slots, grooves, and contouring around the edges of a workpiece.
In peripheral milling, the tool plunges to a set depth, cutting slots or complex contours. It is widely used in industries where edges, deep grooves, and complex shapes (like gears or flanges) are required.
Types of Peripheral Milling
Peripheral milling, like face milling, is one of the fundamental types of milling processes, with several subtypes that follow the same cutting approach but vary in tools and application.
The standard peripheral milling types are:
Slot Milling
It cuts a slot or groove wider than the cutter by plunging and moving the tool.
Straddle Milling
Cutting on one side (or two parallel sides) of the workpiece using the side edges of the cutter.
Form/Contour Milling
This process shapes the periphery of a part with a profiled cutter ( for example, a gear hob or keyway broach).
Slab Milling
It employs a wide cutter that extends beyond the workpiece for big cuts.
Cutting Tools for Peripheral Milling
Peripheral milling often uses single-piece cutters made for side engagement. Some peripheral milling cutters are
Different Profile End Mills: It’s the most common type of peripheral cutter. End mills have helical flutes around the body and cut with the sides and tip simultaneously
Solid end mills (single-piece) come in various profiles. For instance, there are square end mills for flat-bottomed slots and contours, ball-nose end mills for 3D contours and fillets, and corner-round end mills for chamfers and rounded edges.
Slab Mills (Straddle Cutters): These are wide cutters with teeth on the circumference (sometimes on sides), designed for heavy cuts on wide surfaces or keyways. Slab milling cutters may cut on both sides (straddle).
Advantages
There are numerous benefits that plain milling has over other types of processes:
- It can cut intricate contours, tight radii, and deep slots.
- Can achieve a fine finish on contoured surfaces.
- A single-end mill can perform slotting, pocketing, and contouring
- Excels on long, narrow parts or keyways
Disadvantages
Some limitations of peripheral milling are:
- Slower on broad surfaces; may need multiple passes to complete the job.
- Deep slots or pockets require long end mills, which can deflect
- Can cause step-over marks if overlap passes are not used
Applications
As hinted in its earlier section, peripheral milling is used in axial cutting operations and profiling. The common peripheral milling applications include;
- Slot Machining: Cutting straight or curved slots/grooves using an end mill or slotter
- Contouring/Profiling: Machining the periphery of a part (e.g., milling a flange, curved profile, or cam contour) with a CNC toolpath.
- Straddle Milling: Using two parallel cutters to machine two opposite faces simultaneously (e.g., grooving two sides of a block).
- Gear Milling: Using a shaped cutter (form cutter or hob) to generate gear teeth, splines, keyways, or other profiled features
- Pocketing: Roughing or finishing inside areas (with an end mill spiral or raster path).
The Key Differences Between Face Milling and Peripheral Milling
The earlier sections focused on individually explaining the processes, their pros, limitations, and applications. Now, we’ll be highlighting the differentiating factors that separate face milling from peripheral milling in actual use.
Let’s look at the comparative table overviewing face milling vs peripheral milling.
| Face Milling | Peripheral Milling | |
| Cutting Direction | Axis perpendicular; cuts with tool face | Axis parallel; cuts with tool sides |
| Cutting Depth | Shallow axial cuts | Deeper axial cuts |
| Tool Engagement | Multiple inserts share the load on the face | Side flutes engage along the tool length |
| Surface Finish | Smooth finish on large planes | Fine on contours, scallops on flat areas |
| Tool Design | Multi-insert cutters | Smaller solid end mills |
| Material Removal Rate | High | Lower on flat surfaces |
| Applications | Surfacing, leveling, squaring | Slots, pockets, contours, profiles |
Cutting Direction
One major difference between peripheral milling and face milling is the completely different cutting directions. In face milling, the cutter’s axis is perpendicular to the part, and the cutting edges on the face (bottom) of the tool do the work. In peripheral milling, the cutter’s axis is parallel to the part’s surface, and cutting occurs along the side (circumference) of the tool
Cutting Depth
The face milling cutters are focused on flattening the surface; their inserts have limited reach, so a very shallow axial depth is reached per pass.
In the case of peripheral milling, their versatility is based on the use and type of end mill. In most cases, you can often achieve deeper cuts (axially) by plunging or ramping an end mill, though practical depth is limited by tool length and rigidity.
Tool Engagement
Comparing tool engagement in face milling vs peripheral milling, Face mills engage the workpiece with the tool face and rim, which distributes contact across many inserts; each insert sees only a portion of the cut. Hence, the wear and tear is also distributed across the inserts, which kind of enhances tool life.
Peripheral mills engage with the side edges of the cutter (in an end mill, all flutes), so the entire cutting edge length along the side is involved. To summarize, face milling uses the tool end, while peripheral milling uses the tool side
Surface Finish and Tolerances
Face milling generally produces flatter, smoother surfaces. Since the cutter’s face is flat and often uses wiper inserts, face milling yields very consistent flatness. The roughness value(Ra) typically ranges from 0.8 to 1.8 µm.
In contrast, peripheral milling can produce fine finishes on contours; however, on a flat plane, it typically leaves scallops or step-over marks. The roughness value(Ra) typically ranges from 3.2 to 6.3 µm. Meanwhile, both face and peripheral milling tolerances range from ±0.13 mm to 0.05 mm, based on the equipment and tooling used in the process.
Tool Design
You can easily predict the process by looking at their tools. Face mills are large, multiple-insert tools (often 3–8 inches or larger). The reason is they have to cut and cover a large surface in a single pass – hence a wide diameter and multiple cutting edges (inserts).
In contrast, peripheral cutters are smaller, typically solid or indexable end mills, designed for side cutting. Their cutting edges are called flutes, which run along the length of the tool body. A typical end mill may have 4–6 flutes and range from ¼″ to 1″ in diameter.
A face mill has dozens of cutting edges on its body, whereas an end mill (peripheral) might have 4–6 flutes on a ¼″–1″ diameter tool
Material Removal Rate
Face milling, with its wide cutter and many teeth, removes material very quickly per pass. Peripheral milling removes less material per pass (smaller tool), so it is slower on large volumes of flat area. However, peripheral can concentrate removal in a slot or narrow region more efficiently.
Milling Speeds and Feeds
Comparing peripheral vs face milling speeds and feeds, peripheral milling speeds(RPM) are slower, and feed rates are higher than face milling. It is because face mills involve multiple inserts and higher tool engagement.
Cutting Speed(RPM)= (Vc×1000)/π×D
Feed Rate( (mm/min))= RPM× f × Z
Moreover, you can use an online face milling feeds and speeds calculator to find out the exact values of feeds and speeds.
Applications
Face milling is typically used for various types of surface operations: flattening a surface, making square edges, or final cleanup of a large face.
Peripheral milling is used for slots, pockets, contours, and edges; we would say it can be used for anything requiring the tool to move along a path around the part’s perimeter.
How To Choose Between Face and Peripheral Milling?
Selecting between face and peripheral milling depends on part requirements and constraints. You should consider these factors while making a choice:
Geometry
You need to assess part geometry first: What portion of the part needs machining? Flat area vs profile? If more than 50 % of the surface is flat and accessible, then choose face milling. If most of the features are grooves, contours, and narrow walls, peripheral milling is the most suitable option.
Desired Finish
If you require very tight flatness or a smooth planar finish, then we recommend face milling. However, if precision in sidewalls or shapes is required, then peripheral milling is best. Overall, for any job that requires a better surface finish, choose face milling.
Cost
In scenarios where a job is possible with both, but you’ve cost constraints, then peripheral milling might be the cost-effective option. Face mills and their inserts are more expensive per tool than simple end mills. However, they remove material faster. Peripheral milling tools are cheaper but may take longer (thus, more machining time).
In most practical cases, machinists follow the hybrid approach. They rough large flat areas with face milling, then switch to peripheral milling for finishing or profiling. This balance gives an optimal cost/quality trade-off.
How RapidDirect Can Help?
If you’re an engineer, product designer, or manufacturer looking for face milling, peripheral milling, or any other CNC machining services, RapidDirect is equipped to support your project. We offer a full suite of CNC milling services using state-of-the-art 3-axis, 4-axis, and 5-axis machines.
Our team of engineers and machinists reviews your design, tolerances, and material requirements, then recommends the most suitable and cost-efficient machining approach. Our custom milling services cover all common metals and support tight tolerances as low as ±0.05 mm.
Whether you need a single prototype or a full production run, we have the equipment and personnel to handle it with consistent accuracy.
Summary
Face and peripheral milling are two fundamental milling operations. Understanding the difference (peripheral milling vs face milling) matters because many other milling sub-types depend on these core cutting mechanisms.
Face milling cuts with the tool’s face to create a flat, uniform surface. Peripheral milling uses the tool’s sides to machine slots, edges, and contours along the part profile.
In practice, you rarely debate on peripheral vs face milling or choose one method exclusively. Machinists often switch between the two in the same job. A common workflow is to start with face milling to level or rough a surface, then follow up with a suitable peripheral milling process to complete features such as slots, pockets, or profiles.
Work with RapidDirect to get expert guidance and achieve the best machining performance at an optimized cost.
FAQs
What is face milling used for?
Face milling is primarily used to flatten large surfaces. It removes material from the top face of a workpiece to create a smooth surface. Typical uses include surfacing plates, squaring up stock, and preparing a reference surface before further machining.
What is the difference between end milling and face milling?
One of the major differences between end milling and face milling is the tool used. An end mill has a smaller diameter and cuts with both its sides and tip. In contrast, a face mill is a larger tool that only uses its face (bottom) to cut. Face milling for creating flat surfaces, while an end mill normally plunges into material, creating slots and profiles.
How does tool engagement affect the surface finish?
The way the cutter teeth engage the workpiece strongly influences the finish. For instance, in the case of face milling, when multiple teeth on the flat face are engaged, we naturally get a flatter finish. However, in peripheral milling, when you cut along a path, it can leave scallops unless overlapped correctly.
