Why do most nonmetallic clutch facings have grooves cut across their surface?

Nonmetallic clutch facings typically have grooves cut across their surface primarily to prevent sticking and clutch drag. The grooves serve several important functions that contribute to the effective operation of the clutch system.

Firstly, these grooves allow for better dissipation of heat that builds up during clutch engagement and disengagement. When the clutch is engaged, friction generates heat, and without proper ventilation, this heat can lead to the facings sticking together, resulting in clutch drag. The grooves promote airflow, helping to keep the surfaces from overheating and sticking.

Secondly, the grooves help channel away any contaminants, such as oil or dust, which could interfere with the smooth operation of the clutch. By providing pathways for debris to escape, the grooves contribute to maintaining a consistent contact surface, which reduces the likelihood of the clutch sticking.

While enhancing clutch engagement and improving wear resistance are also important factors related to clutch performance, the primary purpose of the grooves in nonmetallic clutch facings is to ensure effective separation and movement of the surfaces, thus preventing unwanted sticking or dragging during operation.