SKFNN-3018-KMC/C481Double Row Cylindrical Roller Bearing 90x140x37 mm 1:12 Tapered Bore Machined Brass Cage P5

Product Description

What this part is

An SKF NN 3018 K M /C481 double-row cylindrical roller bearing, 90 x 140 x 37 mm, with a 1:12 tapered bore, a machined brass cage and P5 precision tolerances.

Decoding the designation

NN — double-row cylindrical roller bearing.
3018 — dimension series and 90 mm bore size code.
K — tapered bore, 1:12 taper.
M — machined brass cage.
P5 — precision tolerance class.

Bore form and mounting

The 1:12 tapered bore seats directly on a matching tapered spindle journal. Radial internal clearance is set at assembly by how far the bearing is driven up the taper, so clearance becomes an adjustment rather than a fixed catalogue value. This is the machine-tool spindle case: the bearing goes straight onto the ground taper on the shaft.

What these specs mean in practice

Two rows of cylindrical rollers give very high radial capacity and very high radial stiffness in a short axial length, which is what a boring or milling spindle needs behind the nose bearing. The rollers run on a plain inner raceway with no ribs to trap them axially, so the bearing carries radial load only and lets the shaft float axially through it — axial location comes from a separate thrust or angular contact bearing elsewhere in the arrangement. A machined brass cage tolerates high speed, shock loading and high temperature better than a pressed steel cage and allows a full roller complement to be guided accurately. P5 tolerances hold bore, outside diameter and raceway runout tight enough to keep spindle runout within a few microns.

Published specifications

Bore: 90 mm (3.543 in), tapered 1:12
Outside diameter: 140 mm (5.512 in)
Width: 37 mm (1.457 in)
Rows: 2
Rolling elements: cylindrical rollers
Cage: machined brass
Precision class: P5
Load direction: radial; axially non-locating
Closure: open

Quantity and configuration

Sale unit is 1 Pc, one complete bearing with both roller rows and the cage. No adapter sleeve applies to this bearing — the tapered bore mounts on the shaft taper itself.

Fitting notes

The bearing is drawn up the shaft taper against a lock nut, and the drive-up distance sets the running clearance; measurement of the reduction in bore clearance as the bearing advances is the usual way of setting it. The outer ring goes into the housing to a close fit with the ring free to slide axially, since this bearing does not locate the shaft.

Interchange guidance

ISO base NN3018 K in P5 with a machined cage — equivalents include FAG NN3018ASK.M.SP, NSK NN3018TBKRCC1P4 and NTN NN3018KC1NAP5, matched for cage and class. The straight-bore NN3018 M is a related size, not an interchange, since it needs a cylindrical shaft seat. NNU-series bearings of the same bore locate the rollers on the outer ring and are a different design.