RHP7008ETDUMP4Super-Precision Angular Contact Ball Bearing Duplex Pair – 40 mm Bore, 68 mm OD, 15 mm Width, 25 Degree Contact Angle, Medium Preload, Phenolic Cage, ABEC 7, Open

Product Description

What this part is

An RHP super-precision angular contact ball bearing supplied as a duplex pair with medium preload. Bore: 40 mm. Outside Diameter: 68 mm. Width: 15 mm per bearing. Closure: Open. Bore type: Straight. Rolling elements: Ball. Contact Angle: 25°. Cage Type: machined, outer-ring guided. Cage Material: laminated phenolic resin. Bearing Material: carbon chrome bearing steel, BS970 534A99/535A99 or SAE 52100. Precision Class: P4 (ISO Class 4, ABEC 7, RHP class code EP7). Series: ISO series 10 (70xx).

Decoding the designation

7008 — ISO dimension series 10, bore code 08, giving 40 x 68 x 15 mm.

E — 25° contact angle, the legacy RHP form of the current A5 code.

T — machined laminated phenolic resin cage, outer-ring guided.

DU — matched duplex pair with universal face control.

M — medium preload.

P4 — ISO Class 4, ABEC 7, RHP class code EP7.

X3 — 25° in the RHP B-series scheme on the alternate carton designation B7008X3TADUMEP7, where EP7 restates the same precision class.

Load ratings and speed

Dynamic Load Rating: 19.5 kN (19,500 N). Static Load Rating: 15.1 kN (15,100 N). Limiting Speed: 29,700 rpm oil/air; 18,400 rpm grease. Axial Preload, medium: 440 N. Axial Stiffness at medium preload: 168 N per micrometre. Running Accuracy at ISO Class 4: Kia 4 µm, Kea 5 µm. Maximum recommended operating temperature: 120 °C. Lubricant: Grease or oil.

What these specs mean in practice

A 25° contact angle carries appreciably more axial load than a 15° bearing of the same envelope and runs at a lower ceiling speed, which is the usual compromise for a spindle that must take cutting thrust as well as turn quickly. Medium preload gives more stiffness than light preload at the cost of higher running torque and more heat, so it suits shorter or more heavily loaded duty cycles. A phenolic cage is light and retains an oil film well, and it sets the assembly temperature ceiling at 120 °C. Tabulated limiting speeds apply to a single bearing under spring preload with the inner ring rotating; a back-to-back medium-preload pair takes a 0.60 factor and a face-to-face pair a further 50 percent reduction.

Thrust direction and arrangement

A single-row angular contact ball bearing takes thrust in one direction. Assembled as a duplex pair the arrangement carries thrust in both directions and the ground ring-face offset sets the medium preload. Universal face control means any two bearings of this designation may be arranged back-to-back, face-to-face or in tandem and will develop the specified preload when clamped.

Quantity and configuration

Unit Quantity: 2 Pcs, one duplex pair. Number of Rows: 1 per bearing. Width 15 mm per bearing, Total Width 30 mm across the assembled pair.

Mounting data

Shaft abutment diameter d1: 46 mm minimum. Housing abutment diameter D1: 62 mm maximum. Outer ring abutment D2: 63 mm maximum. Chamfer r: 1.0 mm minimum. Chamfer r1: 0.6 mm minimum. Effective load centre a: 20.1 mm. Internal free volume: 8.2 cm³. PCD of lubrication jets: 50.0 mm. Mass: 0.189 kg per bearing, 0.378 kg for the pair.

Interchange guidance

Fafnir 3MM9108WI-CR-DUM is a genuine interchange: the 3MM prefix denotes 25°, CR a phenolic outer-land-riding cage and DUM a medium-preload duplex pair, matching this bearing on all four counts. The current NSK designation is NSK 7008A5TRDUMP4. A 7008C at 15°, or a light or heavy preload variant of the same number, shares the envelope and is a related size. Harmonization Code: 8482.10.50.28.