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Why does a plastic chair usually have a hole in the middle?

Have you ever wondered why there is a hole in the middle of the plastic chair you often use?

11 March, 2024

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Have you ever wondered why the plastic chair you often use has a round hole in the middle? Plastic chairs are a familiar item in our daily lives. They are found at home, in roadside restaurants, or even in the workplace. Have you ever wondered why the plastic chair you often use has a round hole in the middle?

Why do plastic chairs often have a hole in the middle?

The small round hole on the plastic chair plays a significant role.

+ Prevents chairs from breaking when stacked

Some believe that creating a hole in the middle of the chair prevents the chairs from sticking to each other when stacked. While this opinion is not entirely incorrect, even a small hole is enough to prevent the chairs from sticking to each other. So why do we need such a big hole?

In reality, the hole in the middle of the plastic chair plays a significant role in preserving the chair. When a chair is loaded, it creates a large compressive stress that is often concentrated in the middle of the chair, making it prone to breakage. Stress is a quantity that represents the internal forces generated in a deformed object due to external factors such as loads and temperature changes. Compressive stress is the stress state when a material is subjected to compression. In the case of brittle materials, exceeding the stress limit will result in fracture.

+ Facilitates easy transportation

When transporting multiple stacked chairs, we can thread a string through the holes and secure the stack of chairs, avoiding breakage during transportation.

+ Makes it easy to pick up a chair

With the design of a hole in the middle of the chair, we can easily pick up a chair from a stack of chairs by putting our hand through the hole and pulling the chair out. This hole helps maintain a balanced pressure, preventing the chair from “sticking” and reducing the force required to pick it up.

+ Provides ventilation

Sitting for a long time on a plastic chair can cause a stuffy feeling and discomfort. The hole in the middle of the chair is designed to provide ventilation, allowing heat to escape and making us more comfortable when using it.

+ Helps children sit up straight

This is a unique and useful tip for mothers who want to correct their children’s sitting posture. Some creative families even put a stick through the hole to help the child maintain balance while studying. Thanks to this improvised tool with the round hole, parents can feel more at ease knowing that their child is sitting upright while studying. It’s true that “necessity is the mother of invention,” isn’t it?

Why is it a circle rather than a square or any other shape?

Based on extensive research, manufacturers have found that a square or most other shapes will concentrate forces at the corners, resulting in chair breakage and affecting the user. Meanwhile, a circle has no corners, making it better at dispersing forces. Moreover, manufacturers also don’t use oval shapes because circles are simpler and easier to implement.

We rarely pay attention to the small details of our everyday items. A small hole compared to the size of a plastic chair plays such an important role, truly proving the saying “small but mighty.”

Frequently asked questions

The hole reduces the concentration of compressive stress in the middle of the chair. Compressive stress occurs when a material is subjected to compression and can lead to fracture in brittle materials like plastic. By dispersing this stress, the hole minimizes the risk of breakage.

A circular shape disperses forces evenly, as it has no corners. Other shapes, like squares, concentrate forces at their corners, increasing the risk of breakage. Circles are also simpler and easier to implement in manufacturing.

When stacking multiple chairs, a string can be threaded through the holes to secure the stack, preventing breakage during transportation. The hole also allows for easy handling by providing a grip point to pick up a chair from a stack.

Yes, the hole provides ventilation to reduce stuffiness and discomfort during extended periods of sitting. It allows heat to escape, making the chair more comfortable to use.

The hole can help children sit up straight. Some families even use a stick through the hole to help children maintain balance while studying, improving their posture.