Fillet vs Chamfer

Fillet vs Chamfer: What’s the Difference?

A fillet is a rounded corner or edge, while a chamfer is an angled edge where two surfaces meet. Both are used to create smooth, finished edges on objects. Chamfer and fillet design are essential in manufacturing, assembling, and using parts. Both design features can reduce stress concentrations and add aesthetics to your part. However, there are also many differences between chamfer and fillet. The chamfer is generally easier to manufacture and increases the allowance of mating parts. Fillet is expensive to manufacture but usually safer and more durable.

Let’s walk through the content below to learn more about the difference between chamfer and fillet.

What is a Fillet?

Edge before fillet and after fillet

A fillet is a rounding of a part design’s interior or exterior corner in mechanical engineering. Fillet geometry is a line of concave function on an interior corner and a line of convex function when on an exterior corner. Fillets are very common in welded, soldered, or brazed joints.

Fillets are critical in mechanical part manufacturing. Employing fillets on points and lines of expected high stress can reduce the stress concentration of mechanical parts. The fillets effectively increase the strength and load-bearing capacity of the parts by distributing stress over a larger area.

In addition, Machinists often use fillets to eliminate sharp edges that are prone to damage or can cause injury when handling parts.

What is a Chamfer?

Edge before chamfer and after chamfer

A chamfer is an interior or exterior corner with an angle or a type of bevel. Using a chamfer prevents the edges from becoming damaged and helps non-uniform edges appear more uniform.

Machinists add a chamfer to a corner that requires high-stress concentration because it focuses the mechanical stress in a specific section. Chamfers are commonly used in machining, furniture, carpentry, concrete formwork, mirrors, and the assembly of mechanical engineering designs.

Chamfers are usually at 45° or 60° from the horizontal. It is often used to deburr from drilling operations when the chamfer is at a 45° to the horizontal. Also, it allows the head of the screw or bolt to sit below the surface instead of sticking out.

A 60° chamfer is typically used as a screw or bolt lead-in. Chamfers are less effective at reducing stress concentrations than fillets because of their sharp corners.

Why Design Fillets and Chamfers for the Parts?

Parts with fillets and chamfers

We often see chamfer and fillet designs in many parts. The reasons for designing chamfers and fillets for parts are mainly for safety, process, and appearance decoration.

#1 Provide Safety

After the parts are milled, the corners are often very sharp. Chamfer and fillet are often used to remove sharp corners and burrs to avoid scratches. The machinists can also use chamfer and fillet to remove the stress on the tip of the part, reducing the damage to the product caused by bumps.

#2 Process Requirement

Due to process requirements, some parts must be designed with appropriate chamfers and fillets. Designing chamfers in shaft-hole mating parts facilitates assembly. Applying chamfers on the tooth top of the gear can prevent heat treatment deformation from causing the top of the tooth to warp. 

And the corners of the part structure are designed with chamfers or fillets to facilitate the smooth circulation of liquid in the mold, uniform pressure, and easy demolding.

#3 Decorative Purpose

Chamfers and fillets also have a decorative effect. The fillet design makes the part more friendly and attractive. When the chamfering radius is not large, a tough and delicate “line” will be formed, which can reflect the delicacy and overall sense of the part process.

When do You Need Fillet and Chamfer?

In part manufacturing, the random use of fillets and chamfers can result in unnecessary processing costs. Knowing when to use chamfers and fillets will help us reduce manufacturing costs and increase the efficiency of our parts.

#1 Add Fillet and Chamfer to the Hole

A fillet is not a good choice if your part includes a hole where screws or bolts will be driven. It will obstruct the smooth movement of the bolt or screw into the hole. In this case, you’ll need a chamfer. The sharp edge of the chamfer will promote smoother pin movement down the hole and easier fastener insertion. 

#2 Add Fillet and Chamfer to Edges of the Part

Chamfers are not always the best choice for the edge of a part. The sharp edges are more likely to wear down parts and cause operator injury. But chamfers are safer than sharp corners because their edges are hidden.

Engineers tend to choose fillets for part edges. Fillets reduce stress on a part and distribute stress over a larger surface, helping to prevent the sudden deformation of compressed parts. At the same time, it is also the best choice for eliminating sharp edges.

#3 Add Fillet and Chamfer to Outside Edges

chamfer for outside edges

Both fillets and chamfers can be used on part outside edges. When you do not have high requirements for the exterior edge design, you can choose chamfers instead of sharp corners to reduce the risk of injury during use.

If the outside edges of the part are aesthetically dominant, fillets of the required radius can be used. Something to keep in mind is that as the radius of the fillet increases, it will help relieve stress and make the design look better.

#4 Add Fillet and Chamfer to Mating Parts

Chamfers are more forgiving than fillets when assembling mating parts. The chamfered holes allow for smooth movement and insertion, making them ideal for easy assembly of male parts to female parts. Moreover, chamfers of different sizes can be created with one tool.

Fillet vs Chamfer: What are the Differences between Fillet and Chamfer?

difference between fillet and chamfer

A fillet is a rounded corner that removes sharp edges or corners on a manufactured part. It is typically used to improve the appearance and safety of the part, as well as to increase its strength and durability. A chamfer is a beveled edge used to remove sharp edges or corners on a manufactured part. It is typically used to improve the appearance and safety of the part, as well as to make it easier to assemble and fit into other components. The main difference between a fillet and a chamfer is their shape – a fillet has a rounded corner, while a chamfer has a beveled edge.

The following table visually shows the main differences between fillets and chamfers to help you get the desired shape in your part design. Let’s take a closer look.

Differences between Fillet and Chamfer
FilletChamfer
SafetyFillet makes the material handling safer.The sharp edges of chamfer can cause injury.
UseFillet can avoid sharp edges from hurting people. Internal features often use fillet.Holes use chamfers for lead-ins. Chamfer is often used for external features.
CostIf it is milling, relatively speaking, the cost of fillet is higher than that of chamfer.The cost of chamfer is slightly cheaper when the part is cut by hand.
Machining TimeCurved edges are not very easy to make. Unless a ball end mill is used for machining complex shapes, it is more time-consuming than chamfer.Chamfer takes less time to process than fillet.
Cutting ToolsDifferent cutting tools are required to machine fillets of different radius.Chamfers of diffrent sizes can be machined with one cutting tool.
CoatingFillet is preferred when coating is required.There are still sharp edges at the chamfer, and the coating is easy to peel off.
Stress Concentration
Fillet shares stress over a larger radius, preventing deformation of the part.Stress is concentrated on a part, which can easily cause deformation of the material.

How to Choose between Fillet and Chamfer?

Here are a few things to help you choose fillets and chamfers for your part design.

Stress Concentration and Safety

The transition part of the fillet is smooth, without sharp points and edges. A chamfer creates a bevel. No matter how the slope angle changes, both sides of the bevel will form sharp corners with the part outline. These sharp corners are obtuse and not sharp. 

Therefore, fillets are more suitable for reducing stress concentration than chamfers, and the protection performance of rounded corners is better than that of chamfered corners.

Part Assembly 

The chamfer often acts as a lead-in for easy assembly, but interference must be avoided. Take the fillet and chamfer in the figure below as an example. 

To ensure that there is no interference when the external chamfer is assembled with the inner fillet and the inner chamfer, the external chamfer must be larger than the inner fillet and inner chamfer. 

Similarly, when the external fillet is assembled with the inner fillet and inner chamfer, the external fillet must be larger than the inner fillet and inner chamfer.

Diagram of fillet and chamfer

Machining Efficiency 

Filter and chamfer can be completed in machining by cutting, grinding, and other processing methods. However, the processing range of chamfer is wider than that of fillets, and it is easier to process.

An example of processing a shaft part. The chamfer can be machined with an ordinary turning tool when using an ordinary lathe. But machining the fillet requires a special forming tool. On the other hand, the efficiency of machining chamfers with CNC machining tools is higher than that of fillets.

Economy and Cost

In terms of economy, the chamfer is better than the fillet. When there is no special requirement, the chamfer is preferred for the external surface and plane of the part.

The side wall of the inner cavity should choose fillet as much as possible because the tool uses the side-edge cutting process. And then, the tool would leave the radius while turning at corners.

If the side wall of the inner cavity is processed into a chamfer, auxiliary processing equipment such as EDM is required. In this case, relatively high costs will be incurred.

Prevent Rust

Without adequate coatings, parts are more prone to rust. The fillet design prevents parts from accelerated rusting because the fillet allows coatings and paints to be evenly distributed. 

Chamfer has a sharp edge and therefore reduces the thickness of the coating. In general, chamfers are not recommended for protective coatings and paints.

Part Aesthetics

Engineers use chamfers and fillets to improve a part’s appearance. The fillet or chamfer is chosen based on the part’s aesthetic requirements. 

In industrial design, Fillets are preferred over chamfers because it makes the design more attractive.

Manufacturing Process

Machining Radius

When adding fillets or chamfers during part manufacturing, consider the following points.

  1. A fillet parallel to the machining axis is simple to add. On the other hand, adding a fillet in a perpendicular direction will raise the part cost. Therefore, performing a chamfer in a direction perpendicular to the machining axis is recommended.
  2. A single tool can produce chamfers of varying sizes. However, we need to use a radius-specific tool to create a different-size radius.
  3. A chamfer may take less machining time in a manual operation than a fillet.
  4. Fillets can improve the material flow during the casting and injection molding process.

Hole Function

a hole using a chamfer

The function of a hole or slot influences the choice between fillets and chamfers. Chamfers are a better choice if the holes are used for pin insertion, screw drive, and bolts into the part.

How to Save Costs for Your Fillets and Chamfers?

While chamfers and fillets are aesthetically pleasing and simple to design, they can also add to a part’s machining time and production cost. So how can we save the cost of chamfering and filleting?

#1 Avoid Tight Tolerances if Possible

The tighter the tolerance, the more expensive the part will cost. Tighter tolerances require more frequent inspection of chamfers. This means higher costs.

#2 Consider Part Production Volume

If only a few parts are manufactured, the cost per part is already high. Then it is not cost-effective to add a chamfer or fillet design.

But for mass production, the cost per part does not increase much. In this case, it is cost-effective to add chamfers or fillets. Casting or forging processes are used for high-volume production, and parts that include fillets are cost-effective.

Conclusion

Fillets are typically used on corners where two surfaces meet at a sharp angle, while chamfers are used on edges where the surfaces meet at an angle.

Parts with fillets are more durable and able to withstand greater loads. Chamfers are best suited when designing mating parts. Choosing the proper fillets and chamfers is critical to the part’s practical design, aesthetics, cost-effectiveness, longer life, and safety.

Are you still confused about choosing fillets and chamfers for your designs? Contact LEADRP today for advice. As a leading CNC machining service provider, LEADRP has an experienced engineering team that can efficiently complete your parts quickly.

References

Fillet (mechanics) – From Wikipedia

Chamfer – From Wikipedia

Fillet vs. Chamfer: What is the difference Between a Fillet and Chamfer – From SMLease Design

Fillet provides superior stress flow (less resistance) than chamfer. Typically, fillets have a lower stress concentration factor than chamfers. When fitting mating components, chamfers are more forgiving.

Chamfers ease the edges of furniture like table tops to prevent people from bruising themselves in otherwise sharp corners. 

A chamfer is technically a type of bevel. The difference between the two is that a bevel is a sloped edge, whereas a chamfer is an edge that connects two surfaces at a 45° angle. A bevel's slope can be any angle other than 90° or 45°.

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