Annular groove and lubrication holes
To facilitate efficient lubrication, all bearings in the NNU 49 series and bearings in the NN 30 series with a bore diameter d ≥ 140 mm, have an annular groove and three lubrication holes in the outer ring (fig.1, designation suffix W33).
Bearings without an annular groove and lubrication holes are typically lubricated either with the requisite minimum quantity of grease or with accurately metered, small quantities of oil or oil-air. In this case, the lubricant is delivered through a nozzle, positioned to the side of the bearing (fig.2, → product table).
If NN 30 series bearings with a bore diameter d ≤ 130 mm (table 1) require an annular groove and lubrication holes, check SKF for availability early in the design phase.