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

7209 — single-row angular contact ball bearing, 45 x 85 x 19 mm, 72-series section29° — the contact angle of the MRC 7000 seriesDU — duplex universally ground, so two bearings of this designation mount together in DB, DF or DT arrangement without shimsP4 — 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 mmOutside diameter: 85 mmWidth: 19 mm per bearingStacked width of the pair: 38 mmRows: 1 per bearingContact angle: 29°Precision class: ABEC 7 / ISO P4Closure: open

Quantity and configuration

Two bearings ship as one matched pair. Spacer rings, lock nuts and housings are not included.

Fitting notes

The high shoulder on the outer ring marks the contact angle direction and sets the arrangement. Back-to-back carries moment load and is the usual spindle configuration; face-to-face tolerates slight misalignment; tandem doubles thrust capacity in one direction. ABEC 7 running accuracy survives only on shaft and housing seats held to matching roundness and cylindricity tolerance, and the bearings mount with even axial pressure on the ring face rather than through the balls.

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.