What is the purpose to conduct grease cone penetration test?

The cone penetration value gives information on the consistency of the grease. If the cone sinks deeper into the grease, the grease has a lower consistency and will flow more easily. The consistency of greases is divided into different classes by the NLGI. Customers use these classes as an indication of how fluent a grease is at 25 degrees Celsius. The cone penetration test is also used as a way to quickly confirm if the delivered grease is on specifications.

In the early days of grease testing the cone penetration test was thought to say something about the viscosity of the grease. However, since those days it was proven that greases do not have one viscosity but that this viscosity is a very complex variable among others dependent on the greases previous history, on temperature and on time. This is why for theoretical research the cone penetration test does not have a lot of value.