MRC7209DUSuper-Precision Angular Contact Ball Bearing Matched Pair 45x85x19 mm 29° ABEC 7 Duplex Ground

Product Description

What this part is

A matched pair of MRC 7209DU super-precision single-row angular contact ball bearings, each 45 mm bore by 85 mm outside diameter by 19 mm wide. They are spindle-grade bearings, universally ground so the two mount together as a set, for machine tool spindles, precision gearboxes, high-speed pumps and rotary tables.

Decoding the designation

Base number: 7209, a single-row angular contact ball bearing, 45 x 85 x 19 mm, 72-series section. Contact angle: 29°, the angle of the MRC 7000 series. DU: duplex universally ground, so two bearings of this designation mount together in DB, DF or DT arrangement without shims. P4: ABEC 7 precision class.

What these specs mean in practice

The contact angle is the spec that defines this bearing, and MRC’s 29° is unusual: the ISO schemes cluster at 15°, 25°, 30° and 40°. At 29° the bearing carries close to the thrust load and axial stiffness of a 30° bearing while retaining most of the speed capability of a 25°. That makes it well suited to spindles where a heavy axial cutting load meets a high spindle speed.

It also means an MRC 7209 is a genuinely different part from a 7209C at 15° or a 7209AC at 25°, even though the three share the same 45 x 85 x 19 mm envelope and will all physically fit the housing. Swapping between them changes spindle stiffness, thrust capacity and the axial load a paired set develops.

Universal grinding is what makes the pair work as a set: the faces are finished so the two bearings sit at a defined preload in back-to-back, face-to-face or tandem arrangement, with no shim stack or measurement at assembly. ABEC 7 class holds bore, outside diameter and running accuracy to super-precision limits, which is what keeps spindle runout within a few microns.

Published specifications

Bore: 45 mm. Outside diameter: 85 mm. Width: 19 mm per bearing. Stacked width of the pair: 38 mm. Rows: 1 per bearing. Contact angle: 29°. Precision class: ABEC 7 / ISO P4. Closure: open.

Quantity and configuration

Two bearings ship as one matched pair. 2 Pcs. Bearings only; spacer rings, lock nuts and housings are supplied separately.

Interchange guidance

A genuine substitution is another MRC 7209-series duplex-ground P4 bearing at the same 29° angle. Bearings of this envelope from other makers carry different contact angles — 7209C at 15°, 7209AC or 7209A5 at 25°, 7209A at 30°, 7209B at 40° — and are related sizes rather than equivalents. Matching the envelope alone is not enough to match the bearing.