QUESTION 33 OF 37

Why are sharp corners on internal geometry very difficult to machine?

This is a question that is often asked to gauge whether or not the candidate understands how to design parts for machining operations. Consider a case where you have designed a perfectly rectangular slot inside a block of steel. Because most basic cutting tools are round, it will not be able to leave a corner that is sharper than the radius of the tool itself. Special tools and processes are needed to create sharp corners, and internal features are much simpler to produce if they do not have sharp corners. Another option is an undercut, which extends the cut by one-half of the tool's diameter to create a pocket for a square part to fit in.

"The reason sharp corners on internal geometry are difficult to machine is that most cutting tools are round, so they remove material with a fillet equal to the tool's radius. You can avoid this by including a radius in the design, or adding an undercut feature for manual or CNC machining. I know that there are ways to machine sharp corners internally, but they are very timeconsuming and expensive, and therefore not necessary for most designs."

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Mechanical Engineer Mock Interview

Why are sharp corners on internal geometry very difficult to machine?

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37 Mechanical Engineer Interview Questions & Answers