RHP7008CTDUMP4Super Precision Angular Contact Ball Bearing – Straight Bore, 40 mm ID, 68 mm OD, 15 mm Width, Open, 15° Contact Angle, Medium Preload, Universally Ground

Product Description

What this part is: RHP 7008CTDUMP4 super-precision single-row angular contact ball bearing, one bearing from a universally ground duplex pair. Bore: 40 mm. Outside Diameter: 68 mm. Overall Width: 15 mm. Contact Angle: 15°. Number Of Rows: 1. Bore Type: Straight. Closure Type: Open. Rolling Elements: chrome steel balls. Bearing Material: carbon chrome bearing steel to BS970 534A99 / 535A99, equivalent to SAE 52100, through hardened and heat treated for stability. Decoding the designation: Series: 7000, ISO dimension series 10. Bore code 08 gives a 40 mm bore. Contact Angle: 15°. Cage Material: laminated phenolic resin. Cage Type: machined, outer-ring guided. Arrangement: DU, a paired unit. Preload: Medium. Precision Class: P4. The carton carries the same bearing in three schemes and all three agree on the angle: RHP 7008-C-T-DUM-P4, RHP B-series B7008X2TADUMEP7, and Fafnir 2MM9108WI CR DUM. Searchable variants: 7008C, 7008 C T DUM P4, 7008CTRDUMP4, B7008X2TADUMEP7, 2MM9108WI. Load ratings and speeds: Dynamic Load Rating: 20.6 kN, 4,631 lbf. Static Load Rating: 15.9 kN, 3,574 lbf. Limiting Speed: 34,000 rpm with oil-air lubrication and 21,000 rpm with grease. The two figures differ because oil-air carries heat out of the bearing and continuously replenishes the film, while grease lubricates without cooling. Mounted as a medium-preload back-to-back pair the limiting speed carries a factor of 0.60; face-to-face mounting halves it again. Lubricant: oil or grease. What these specs mean in practice: A 15° contact angle favours speed and radial stiffness over thrust capacity, which is what a machine tool spindle wants. Medium preload trades speed for rigidity: Axial Preload: 290 N as a pair, against 120 N for light preload on the same size, and Axial Stiffness: 77 N per micron against 51 N per micron light. Effective Load Centre: 14.7 mm. Maximum Operating Temperature: 120°C, set by the laminated phenolic resin cage. A phenolic cage is light, quiet and self-lubricating, and it rides on the outer ring land so the cage is guided by the slower-moving ring. Min Temp: -30°C. Precision and running accuracy: Precision Class: P4. Precision Rating: ABEC 7, ISO 492 Class 4, BS292 EP7. Deviation of mean bore diameter: 0 to minus 5 microns. Deviation of mean outside diameter: 0 to minus 5 microns. Radial runout of the assembled inner ring: 4 microns maximum. Radial runout of the assembled outer ring: 5 microns maximum. The high point of radial runout is marked by a burnished spot on the inner ring face and by a V line on the outer ring outside diameter, and the V also gives the direction of the contact angle. Mounting data: Shaft abutment diameter d1: 46 mm minimum. Housing abutment diameter D1: 62 mm maximum. Outer ring abutment diameter D2: 63 mm maximum. Bearing fillet radius r: 1.0 mm minimum. Inner fillet radius r1: 0.6 mm minimum. Internal Volume: 8.2 cubic centimetres, which is the figure grease quantity is calculated from. Lubrication jet pitch circle diameter: 50.0 mm. Item Weight: 0.42 lbs, 0.189 kg. Quantity and configuration: Unit Quantity: 1 Pc. One bearing from a universally ground duplex pair. Universal face control means the inner and outer rings are the same width and the face relationship is ground at manufacture to give the medium preload, so it combines back-to-back, face-to-face or in tandem with another bearing of the same designation without ground spacers, and shares load equally in tandem. Two bearings mounted together give a total width of 30 mm. Interchange guidance: NSK 7008CTRDUMP4 is the same bearing under NSK’s name. Fafnir 2MM9108WI CR DUM and FAG B7008-C-T-P4S-UM are 15° medium preload in P4S tolerance, and SKF 7008 CDGB/P4A is 15° medium preload in the P4A class, all at 40 x 68 x 15 mm. The 25° 7008A5 has the same 40 x 68 x 15 mm size but a different contact angle, which sets both thrust capacity and speed limit.