Chamfer or Fillet: It’s More Than a Coin Toss
Hailey Kupiec posted on July 19, 2016 |

First, a terminology review: in design and machining, a chamfer is a sloped or angled corner or edge, and a fillet is a rounded corner or edge. These edges can be located on either the interior or the exterior of a part.

However, applying a chamfer on an inside pocket is not a popular practice, explained Eng-Tips Forums user AJACK.

 

So the question is, “How do you choose between chamfering or filleting a sharp corner. Are there any factors to consider besides flipping a coin?” as asked by jamesyboy1990, a member of Eng-Tips Forums.

To try and shed some light on this question, the following are some basic factors to consider when making your machining decisions.

   

Comparison Between Chamfer and Fillet for External Edges

Whether you choose to go with a chamfer edge, or a fillet edge, will often depend on factors in your project such as budget and time constraints. The chart below compares some of these considerations:


 

Chamfer

Fillet

Cost

Less expensive if the part is being machined manually

If the part is being milled, the cost will be equal to that of a chamfer

Time

It is usually faster to apply a chamfer

Usually less time effective unless a round mill is already being used to mill complex, curved surfaces

Tooling

“Within reason one tool can create chamfers of different sizes” – KENAT on Eng-Tips Forums

Fillets require specific size tools to produce different fillet sizes.

Coatings

Due to the sharpness of chamfer corners, paint or protective coatings will draw back from the edge. This means that the coating near the edges will wear more quickly.

For a smooth, even application of the paint or coating, a fillet is a better option.

Which Method is the Most Popular?

Fillets give a part better flow and less resistance. Using a fillet also eliminates any sharp edges that can be easily damaged, or that could cause injury when the part is handled. This means there is less risk of failing an inspection for having a burr or sharp edge. Fillets also have lower stress concentration factors, meaning that they distribute stress over a broader area. This makes filleted parts more durable, and able to withstand larger loads.

Chamfers are more forgiving when designing to fit mating parts, but overall it appears that designs using fillets are preferred by senior management, industrial designers and many others according to forum user KENAT.

“On a finishing turn, I would always put a 0.010 fillet on every corner because when turning any angular turn the tool tip will leave the finished surface and could cause a sharp edge. The extra time is undetectable but the lack of sharp edges will be a joy to your customer and you,” said forum user BillPSU.

Want to join the conversation? Head over to Eng-Tips Forums. To discuss this article, click here.

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