What is a Nuts?

Now that we've covered bolts, their "perfect partner" — the nut — is much easier to understand.

Simply put, a nut is a small metal block or disc with a round hole in the center and internal threads on the wall of that hole. Its core function is to work with an externally threaded bolt to clamp two or more components together through rotational force.

Think of a nut as a "toothed sleeve" — the internal threads (teeth) on its wall mesh perfectly with the external threads (teeth) on the bolt's shank. When the bolt passes through the parts to be joined and the nut is screwed on and tightened, the threaded pair generates tremendous axial clamping force, firmly holding the objects in place.

Anatomy and Key Specifications

A standard nut consists of two main parts:

• Outer Shape: The most common is a one-piece hexagonal shape (for wrench access). There are also round types (with cotter pin holes), square types, and flange types (with an integrated washer effect).

• Internal Threads: This is the most critical functional feature. The thread specifications (e.g., diameter, pitch) must exactly match those of the mating bolt, or they will not engage.

Three core specifications define a nut:

1. Nominal Diameter: The diameter of the bolt it mates with (e.g., an M8 nut fits an M8 bolt).

2. Width Across Flats: The wrench size needed to turn it (e.g., an M8 nut typically uses a 13mm wrench).

3. Height/Thickness: Affects the number of thread engagement turns. Greater thickness generally means higher tensile load capacity.