Understanding the Difference Between a Fillet and Chamfer

For actual use or processing needs, there are small bevels or fillets at the corners or connections of many parts and equipment. Fillets and chamfers can be seen everywhere in design drawings, especially mechanical design drawings.

In this article, experts from YIJIN Hardware will tell you what is a fillet and what is chamfering. What is the difference between chamfer and fillet?

What is a Fillet?

The fillet is to replace the original corner with an arc that is tangent to both sides of the corner. The size of the fillet is represented by the radius of the arc. In the design of precision parts, the application of rounded corners has become more and more extensive.

Precision part design engineers use fillets to relieve stress on parts. Fillet help distributes stress evenly over a larger surface, preventing rapid deformation of the part. 

What is a Fillet?

What is a Chamfer?

Definition of Chamfering:

Chamfering is the removal of “dumped” corners that have already been formed. 

The chamfer does not necessarily have to be a 45-degree facet, as long as the top of the corner is ground flat, it is a chamfer, and it is often made 45 degrees in machining. The purpose of chamfering is mainly to prevent the sharp angle formed during the processing of hard objects from causing damage to other objects or people, and the chamfering of the hole can also facilitate the function of the movement of the coupling in the hole.

chamfer

What Do Chamfers and Fillets Do on Parts

The functions of chamfering are as follows:

  1.  Remove sharp edges (for safety’s sake).
  2. Guide (facilitates assembly).
  3. Remove burrs and make them beautiful.

The Functions of Fillets are as Follows:

  1. Process fillet (casting parts must have fillet transitions where the size changes drastically).
  2. Prevent the gravitational concentration of the workpiece.

Screw Design with Chamfered Edges

Chamfers can be widely used both internally and externally in mechanical design. Under certain conditions, the chamfer usually forms an angle of 45° with the horizontal plane, which is greatly beneficial to bevel the edge of the hole after drilling. The design requires a part to drive the screw and to keep the screw head from sticking out, then a chamfer is needed. Of course, there are also cases where larger chamfers are used, such as large chamfers above 60°.

Application Notes for Chamfering

There is a significant problem with chamfers:

The edges are too sharp for handling. Many workers are often scratched when handling chamfered parts and equipment, and the sharp edges can easily shred work clothes. At this stage, in order to avoid handling injuries caused by chamfering, part design engineers often use the method of breaking the edge of the part to reduce the risk. Of course, Fillet can also be used to avoid the additional hazards of chamfering.

Application Notes for Chamfering

Simple chamfers can break sharp corners, and according to design requirements, part design engineers can use fillets or chamfers on the outer edge of the part. If the original design is not very demanding about the appearance of the part, then you can choose a relatively simple chamfer to break the sharp corners. Conversely, if the original intent of the design is to ensure the aesthetics of the part, then it is best to use rounded corners. The larger the radius, the better the design, after all, the radius fillet has the effect of relieving stress.

If there is a hole in the design drawing of the part design engineer that can drive the screw and bolt, then the use of fillets will prevent the bolt and screw from entering the hole smoothly. The sharp edge will help the pin slide smoothly into the hole, making tightening easier.

Comparison Table Between Fillet and Chamfer

Comparison Table Between Fillet and ChamferComparison Table Between Fillet and Chamfer

Difference Between Fillet and Chamfer

Machining Time: Chamfering is a very good choice for the part being set up if the engineer expects to complete the design in a short time. Compared with fillet, chamfering is not only simple to make, but also takes less time to make. If the precision part can be processed with a CNC milling machine, the advantages of fast chamfering will be more obvious.

Cutting Tool: Due to fillets it has different radii, we need special cutting tools to make fillets. Different cutting tools can make different radii of fillets. For chamfers, we don’t need multiple tools for chamfer design. One cutting tool can make different chamfer sizes.

One cutting tool can make different chamfer sizes

Application Scope of Fillet and Chamfer

They are used not only in mechanical production and processing but also in the field of people’s livelihood. So what fields are involved in the daily application of fillet and chamfering?

Lathe turning tool: The turning tool is about 15 cm long, with an irregular shape on the sides and a sharp edge on the top, which is a chamfer. Chamfering is applied to turning tools, with sharp edges. It can be installed on ordinary lathes to manufacture various parts, such as stepped shafts, and thick and thin shafts.

Clock and watch: From the analysis of the watch alone, because the watch is worn on the wrist, the chamfer will scratch the skin, which has a greater risk. The fillets tend to be rounded and smooth, which improves the safety of wearing.

Table corner: In daily life, tables are widely used, such as dining tables, writing desks, pool tables, consoles, and so on. Fillet or chamfer is determined according to different scenarios and needs. Take the dining table as an example. At present, whether the dining table is quadrilateral or round, the process of chamfer + fillet is adopted. There is a 45° bevel at the edge, and after two sharp edges are formed, the sharp edges form fillets.

There is a 45° bevel at the edge, and after two sharp edges are formed, the sharp edges form fillets.

Fillet and chamfer are important links in industrial production, and also an important nodes for part fit matching. At present, whether the parts are filled or chamfered depends on the design drawings and design assembly on the one hand, and the nature of future use should also be considered. At present, the processing methods of fillet and chamfer are mainly performed by CNC milling machines and machine tools; especially for fillets with high processing difficulty, CNC technology is generally used to complete the operation.

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