Necking (engineering)

So, you know how sometimes you have a drinking straw that has a skinny part in the middle and then gets wider at the top and bottom? Well, engineers sometimes create parts that look sort of like that straw with a skinny part called a "neck."

Necking is a way of making the material stronger in that skinny part. Imagine if you had a paper straw, and you tried to bend it in half. It's probably pretty easy, right? But what if you made the middle part of the straw skinnier? Now it might be harder to bend in half. In engineering, necking does something similar. It sort of squeezes the material in that skinny part, making it stronger.

So why not just use a thicker piece of material instead of using necking? Well, sometimes that's not possible, either because of cost or because it just won't fit in the space you need it to fit in. So instead, engineers use necking to make a part stronger without needing to make it thicker.