What Is a Spherical Washer?
A spherical washer is a washer that uses two washers together in a set: a concave washer with a flat and spherical surface on one side and a concave-convex washer with a flat and convex spherical surface on the other side.
Spherical washers are used to correct the angle of the shaft of a tap or bolt that has been tightened at an angle and cannot be removed.
When a bolt is angled, only a portion of the axial force applied to the bolt is transmitted to the base metal, which reduces the axial force on the base metal, and the remaining force is consumed as a frictional force in the gap.
The angle that can be compensated by a spherical washer is about 3 degrees. If the angle is too large, using a spherical washer will not be effective, so tightening the bolt as much as possible will improve the force being consumed.
Uses of Spherical Washers
Spherical washers are used to absorb and compensate for the angle of a bolt or tap shaft that has been tightened at an angle.
The spherical washer is placed so that the concave side of the washer contacts the base metal and the convex side contacts the top of the bolt. By tightening the bolt in this condition, the angle of the bolt fixed at an angle is reduced, and the bolt can be tightened so that the seating surface does not float.
It should be noted that the axial force is reduced by not transmitting enough force from the bolt.
Principle of Spherical Washers
Spherical washers use two pairs of concavo-convex spherical surfaces on each side to reduce the inclination created between the bolt and the base metal and correct the tightening of bolts that have been tightened at an angle.
As the inclination increases, the area of the bolt in contact with the base metal becomes smaller, causing it to cave in or slip because the axial force is no longer transmitted to the base metal.
The spherical washer is placed between the angled bolt and the base metal, and when tightened in this condition, the convex spherical surface slides over the concave spherical surface as the bolt is tightened. The convex spherical washer naturally corrects itself to the same angle as the bolt axis, preventing the seating surface from floating and ensuring a secure connection.