What is plain washer ?

A plain washer is a flat disc. It has a hole in its center through which a bolt, stud, or set-screw can pass. By using it, the surface below the bolts or nuts becomes plain. In this way, the pressure of the nut is uniform on the entire surface. This washer is of the following standard:

Diameter of the washer = 2D + 1/8  (D = Diameter of bolts)

The thickness of Washer = 1/8 D

The angle of Chamfer = 30°

Diameter of inner hole = Diameter of bolt

1 Torque Washer

2 Flat Washer

The flat plain washers are thin, flat, and circular in shape with a hole in the center. Flat plain washer application is intended to give the load over a relatively large area and give support to small head screws.

It is also known as Type A plain washers. A flat washer is what most people think of a normal washer. They are good for general use. 

3 Fender Washer

The fender washers are flat washers with a small hole and outside relatively large diameter. Hence this type of plain washer gives loads over a relatively larger area than flat washers.

Fender washers have applications for installing signboards, panels, drywall, automobiles, plumbing, sheet metal, and electrical applications. It is usually a thin metal. They have named it for their general use on car fenders.

4 Finishing or Countersunk Washer

The finishing washer has a top designed to hold the fastener. It is also known as a countersunk washer. The Countersunk washer has 90° or 120° counters at the top.

These washers served as flat washers for flat head counters screws. This gives a flush surface to the countersunk screw.

5 Shoulder Washer

Shoulder washers consist of a shoulder type of structure. They are employed to protect screws, wires, or any element from the rest of the assembly. They are available in fiber-glass, phenolic, nylon, PCTFE, PTFE, and metals.

6 C-Washer

These look like a flat washer, however, it has a slot cut from the center hole to form a “C” shape. A C-washer is made to slide in and out of place on the bolt or shaft.

The C-Washer used at any time may need to be adjusted or replaced, without removing the fastener.