FAGNN3011ASMSPDouble-Row Cylindrical Roller Inner Ring & Roller Assembly, 55 mm Bore x 26 mm Wide, Machined Brass Cage, SP Precision — No Outer Ring

Product Description

What this part is

The inner ring, roller complement and cage of a FAG NN3011-AS-M-SP double-row cylindrical roller bearing, 55 mm bore, 26 mm wide. In the NN design the three guide ribs are machined on the inner ring, which carries both roller rows, and the outer ring is a plain separable sleeve. Inner ring with roller and cage assembly only. No outer ring.

Decoding the designation

NN is the double-row cylindrical roller design with ribs on the inner ring; the reverse arrangement, ribs on the outer ring and a plain inner, is NNU. 30 is the dimension series and 11 the bore code, giving 55 mm at five millimetres per unit; a complete NN3011 measures 55 x 90 x 26 mm. AS is the FAG lubrication groove with radial feed holes, a feature machined into the outer ring. M is the machined brass cage. SP is FAG special precision: dimensional tolerance to ISO class 5, equivalent to P5 and ABEC 5, with running accuracy held tighter than class 5. The absence of a K means a straight cylindrical bore.

What these specs mean in practice

Two rows of cylindrical rollers in a narrow section give a double-row cylindrical bearing very high radial rating and very high radial stiffness for its width, which is why the NN and NNU families are the standard radial bearings in machine tool spindles and precision gearboxes. The bearing locates the shaft radially only; axial location comes from a separate thrust or angular contact bearing in the same spindle. SP precision matters because at this accuracy the bearing’s own runout, rather than the shaft, sets the achievable spindle runout. The machined brass cage handles the speed, temperature and lubricant drag of a precision spindle better than a pressed cage.

Quantity and configuration

1 Pc. Inner ring with its two roller rows and machined brass cage. No outer ring. The matching part is the plain outer ring of an NN3011, 90 mm outside diameter, carrying the AS lubrication groove and feed holes.

Bore form on the NN family

This item has a straight cylindrical bore. Where an NN carries a K suffix the 1:12 tapered bore mounts directly on a tapered spindle journal and no adapter sleeve is used, which is the opposite of a spherical roller bearing, where a 1:12 bore needs an H-series sleeve. On the tapered version, drive-up along the journal sets radial internal clearance.

Fitting notes

The straight bore mounts on the shaft with an interference fit, heated or pressed against the inner ring face. Because the rings are separable, the roller set travels with the inner ring and is brought into a plain outer ring axially. Roller sets and rings are matched at manufacture and are not mixed between bearings, so this assembly pairs with an NN3011 outer ring of the same precision class.

Interchange guidance

The ISO base number is NN3011, so the interchange is another maker’s NN3011 inner ring and roller assembly at class 5 precision with a machined brass cage: NSK NN3011MB, SKF NN3011KTN9/SP or the NN3011-AS-M-SP itself. NNU4911 is a related size, not a substitution, because its ribs are on the outer ring and its rings are not interchangeable with an NN. NN3011K is the 1:12 tapered-bore form and NN3011-AS-K-M-UP is a higher precision class; both are different parts.