# Grease Film Collapse When Spindle dN Crosses One Million

Above roughly 1e6 dN, grease films thin under centrifugal throw-off while churn heat climbs. Outer-ring temperature can rise ten degrees within a few minutes of aggressive run-up. Oil-air metering keeps a micro-dose on the race and uses the air stream as a coolant, so clearance stays closer to the design band.

TFL Bearing explains when grease still belongs and when oil-air becomes the safer default. Keep oil-air lubrication for high-speed spindles open during rebuild reviews.

Shandong TFL Bearing Co., Ltd publishes these limits so process and maintenance share one dN cutoff language.