MRC7108KRDTDBAngular Contact Ball Bearing Matched Pair, 40 x 68 x 15 mm, 15 Degree Contact Angle, ABEC 7, Universally Ground

Product Description

What this part is

MRC 7108KRDTDB, an angular contact ball bearing set. Bore: 40 mm. Outside Diameter: 68 mm. Width: 15 mm. Contact Angle: 15°. Outer Ring Form: counterbored. Precision Class: ABEC 7. Arrangement: universally ground for back-to-back or tandem mounting. Bore Form: straight. Number of Rows: 1 per bearing.

The envelope is the ISO 7008 size, so the bearings drop into a housing and shaft already machined for a 40 x 68 x 15 mm angular contact bearing.

Decoding the designation

7 — MRC’s angular contact ball bearing series. The leading 7 identifies the family and carries no contact-angle information.

1108 — the 71xx dimension block; 7108 is the 40 mm bore in that block and lands on the ISO 7008 envelope.

KR — MRC’s R-type execution: 15° contact angle with a counterbored outer ring. The counterbore is what lets the ball complement be loaded high while keeping one shoulder full-height on the thrust side.

DT — tandem. Two bearings facing the same direction, sharing thrust in one direction.

DB — back-to-back. Two bearings with their load lines diverging outward, taking thrust in both directions and giving the widest effective bearing span for moment stiffness.

BKE#7 — the carton marking on this set.

What these specs mean in practice

Contact Angle: 15°. A 15° angle is the high-speed end of the angular contact range: it takes less thrust per unit of radial load than a 25° or 29° bearing, and runs faster and cooler for it. That is why the 15° R-type ends up on machine-tool spindles and precision gear trains rather than on heavily thrust-loaded pump shafts.

Precision Class: ABEC 7. ABEC 7 tightens bore, outside diameter, width and running accuracy well beyond standard tolerance, which shows up as lower radial and axial runout at the tool or the gear face.

Arrangement: universally ground. The ring faces are ground so that any two bearings from the range butt together and reach the intended preload with no shim and no measurement at assembly. That is the practical value of the DT and DB markings appearing together — the same pair serves either arrangement.

Mounting data

Bore: 40 mm, straight. Outside Diameter: 68 mm. Width per Bearing: 15 mm. Total Width of the Pair: 30 mm.

Back-to-back mounting places the two load lines apart along the shaft, which is the arrangement to choose where the bearing pair has to resist a tilting moment. Tandem mounting places both load lines parallel and doubles the thrust capacity in one direction.

Quantity and configuration

Unit Quantity: 2 Pcs. A matched pair of single-row bearings.

Interchange guidance

The 40 x 68 x 15 mm envelope is the ISO 7008 size, so an SKF 7008 CD/P4A, an FAG B7008-C-T-P4S, an NSK 7008CTYNSULP4 or an RHP 7008 CTDULP4 all match on boundary dimensions and on the 15° angle (SKF CD, FAG C, NSK C and RHP C are all 15°). A 7008 A, AC or E execution from those makers is the same envelope at 25° or 30° and is a related size rather than a substitution — swapping angle changes the thrust-to-speed balance and the preload the set develops. Within MRC, 7107KR is the 35 mm bore and 7109KR the 45 mm bore in the same block.