NSKHR30311DJDBP5Tapered Roller Bearing Matched Pair – 55 mm ID, 120 mm OD, 31.5 mm Width, 28° Contact Angle, Back-to-Back, Class 5

Product Description

What this part is:

NSK HR30311DJDBP5 single-row metric tapered roller bearing, cone and cup, supplied as a matched back-to-back pair. Bore: 55 mm. Outside Diameter: 120 mm. Overall Width: 31.5 mm per bearing. Cone Width B: 29 mm. Cup Width C: 21 mm. Contact Angle: 28°. Precision Class: ISO Class 5, ABEC 5. Cage Material: Pressed Steel. Cage Type: Pressed Steel. Rolling Elements: Tapered Roller. Number Of Rows: 1 per bearing. Bore Type: Straight. Closure Type: Open. Material: High Carbon Chrome Steel. Design Units: Metric. Item weight: 1.58 kg per bearing.

Decoding the designation:

HR — NSK’s high-capacity tapered roller uprate, giving a higher load rating within the same envelope.

30311 — the ISO 30311 metric taper size in the 303 series, 55 x 120 x 31.5 mm.

D — a steep 28° contact angle, which raises thrust capacity.

J — pressed steel cage.

DB — back-to-back matched pair, so the two load lines diverge and the pair takes thrust in both directions with a wide effective bearing spread.

P5 — ISO Class 5, ABEC 5 running accuracy.

What these specs mean in practice:

Dynamic Load Rating: 161 kN. Static Load Rating: 153 kN. Limiting Speed: 2,800 rpm grease / 4,000 rpm oil bath, and 6,000 rpm on mechanical or jet oil. Axial load factor e: 0.83. Y1: 0.73. Y0: 0.4. Effective load centre a: 37 mm.

The 28° angle and the e value of 0.83 mark this out as a thrust-biased taper, carrying a large axial component alongside its radial load. The back-to-back arrangement sets the two effective load centres apart from each other, which gives the assembly a wide support base and high resistance to moment loading on a shaft. Class 5 accuracy holds shaft position and runout closely. Lubricant: Grease or oil.

Mounting data:

Shaft abutment diameter da min: 75 mm. Cone back-face abutment db max: 67 mm. Housing abutment diameter Da min: 94 mm, Da max: 110 mm. Housing abutment Db min: 114 mm. Abutment clearance Sa: 4 mm. Abutment clearance Sb: 10.5 mm. Shaft fillet radius ra max: 2 mm.

Quantity and configuration:

Unit Quantity: 2 Pcs. A factory-matched back-to-back pair, each bearing comprising a cone and its own cup, ground together as a set.

Interchange guidance:

Cross-references: HR30311DJDBP5, HR 30311 DJ DB P5, HR-30311-DJDB-P5, HR30311DJ, HR30311, 30311. A plain 30311 shares the 55 x 120 x 31.5 mm envelope without the HR capacity uprate, the 28° D angle or the Class 5 matched-set grinding, so it is a related size rather than a direct substitution.