The key difference between the fender washer vs flat washer is that for the same inner diameter the fender washer has a larger outer diameter than the flat washer, and thus the fender washer has more bearing surface than the flat washer.

Contents:
Fender washer:
The fender washer is a flat washer with an outer diameter comparatively larger than the inner diameter. For a fender washer, the outer diameter is generally more than 3 times of the inner diameter.
The fender washers have a wider bearing surface that helps to spread the load over the larger surface of the object. Thus it helps to lower the pressure over the object’s surface.
Flat washer:
Flat washers are what everyone thinks about the washer. These are the most used plain circular washers with an appropriate-sized hole at the center.
The basic purpose of using a flat washer is to spread the load over the surface area of the object. Thus it reduces the pressure on the fastened object.
Fender washer vs Flat washer:
Sr. No. | Fender washer | Flat washer |
---|---|---|
1 | The fender washer is a circular washer with an outer diameter larger in comparison with the inner diameter | The flat washer is a plain circular disc made from a thin sheet of material with a hole at the center. |
2 | In this washer, the outer diameter is more than 3 times of the inner diameter. | In this washer, the outer diameter is generally less than 3 times of inner diameter. |
3 | It has a wider bearing surface. | It has a comparatively less bearing surface. |
4 | The fender washers are suitable for covering the oversize hole. | These are not suitable for oversize holes. |
5 | The wider surface of the washer helps to distribute the load due to the tightening of fasteners over the surface of the object. | The fastening load is distributed within less surface area. |
6 | The name of the fender washer arises due to its use for the automobile fender. | The flat washer is named on the basis of its appearance as circular and flat. |
7 | It creates less pressure on the object surface due to the fastening load. | It creates comparatively more pressure on the surface of the object due to the fastening load. |
8 | It is suitable for the fitting of thin-walled components. | It is not suitable for the fitting of thin-walled components. |
9 | The fender washers are used in sheet metal applications, hanging signboards, plumbing, etc. | The flat washers have huge applications in automobiles plumbing, industrial equipment, and much more. |
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