SKF21309AKDouble-Row Spherical Roller Bearing, 45 x 100 x 25 mm, 1:12 Tapered Bore, Normal Clearance

Product Description

What this part is

An SKF 21309 AK double-row spherical roller bearing. Bore 45 mm on a 1:12 taper, outside diameter 100 mm, width 25 mm, open on both faces. Two rows of barrel-shaped rollers share one spherical raceway in the outer ring, so the inner ring and roller set swivel bodily inside the outer ring and the bearing carries load through shaft deflection and housing misalignment.

Decoding the designation

The 213 dimension series is the narrower of the spherical roller series, sitting on a larger outside diameter than the 222 series for a given bore — here 100 mm on a 45 mm bore against the 85 mm of a 22209. The bore code 09 gives 45 mm. K specifies a 1:12 tapered bore. There is no clearance suffix, so radial internal clearance is normal, CN, and no W33, so the outer ring is plain. The A is an SKF internal design-variant letter that is not part of the current published suffix scheme and is carried here as a searchable reference rather than as a specification.

Tapered bore and adapter sleeve

A tapered-bore spherical roller bearing seats on a matching 1:12 taper. On a plain cylindrical shaft that taper is provided by an adapter sleeve, which is a separate part. For a 45 mm bearing bore the sleeve is an H309, whose own shaft seat is 40 mm, supplied with a KM 9 locknut and an MB 9 lockwasher. Driving the bearing further up the sleeve reduces its radial internal clearance, which is how the mounted clearance is set to a measured figure rather than accepted as delivered.

What these specs mean in practice

A double-row spherical roller bearing carries very heavy radial load and takes thrust in both directions, and it tolerates misalignment as a normal service condition. The taper bore is what makes a spherical roller bearing mountable anywhere along a plain shaft without a machined seat, which is why it dominates conveyor and plummer-block work. The 213 series keeps the axial width smaller than a 223 of the same bore, at a lower radial rating — the trade that suits a housing constrained in width.

Quantity and configuration

1 Pc. Bearing only. Supplied without adapter sleeve H309, locknut KM 9 and lockwasher MB 9. Open both faces, with sealing handled by the housing.

Fitting notes

Radial internal clearance is measured with a feeler at the unloaded roller row before mounting and again as the bearing is driven up the taper, and the reduction from the first figure is what sets the fit. The sleeve is locked with the KM nut and the MB washer tab.

Interchange guidance

Same-envelope 45 x 100 x 25 mm tapered-bore spherical rollers include FAG 21309-E1-XL-K, NSK 21309CDK and NTN 21309KD1, all mounting on a 1:12 taper. The straight-bore SKF 21309 A shares the envelope but mounts directly on a cylindrical shaft with no sleeve, and a 21309 EK is the reinforced internal design; both are related sizes rather than substitutions.