The Anahuac Mayab University is a private institution of Catholic inspiration founded in 1984.
They are used in the same applications as fender washers. A spherical washer is part of a self-aligning nut; it is a washer with one radiused surface, which is designed to be used in conjunction with a mating nut in order to correct for up to several degrees of misalignment between parts.
The straightforward, but critical, purpose of a spool pin is to hold the spool of thread in the correct position for the thread feeding mechanisms to work properly. The spool pin must provide stability for the thread spool, but in itself does not provide direct tension for the thread being pulled from the spool.