NSK51111Single-Direction Thrust Ball Bearing – 55 mm Bore x 78 mm OD x 16 mm High, Flat Seat, Grooved Race

Product Description

What this part is

NSK 51111 single-direction thrust ball bearing, ISO 51111 size, flat seat type. Bore: 55 mm. Outside Diameter: 78 mm. Height: 16 mm. Bearing Type: Single-direction thrust ball bearing. Number of Rows: 1. Rolling Elements: Ball. Cage Material: Pressed steel. Dynamic Axial Load Rating: 35 kN. Static Axial Load Rating: 93 kN. Limiting Speed: 2,800 rpm on grease, 4,300 rpm on oil. Item Weight: 0.227 kg.

Decoding the designation

511 — ISO dimension series 11 for single-direction thrust ball bearings with a flat seat.

11 — bore code 11, giving a 55 mm bore.

What these specs mean in practice

A single-direction thrust ball bearing carries pure axial load in one direction. It separates into three pieces: a shaft washer with a 55 mm bore, a housing washer with a 57 mm bore, and a ball-and-cage assembly between them. Both washers are grooved, so the balls run in a raceway rather than on a flat face, which is what gives the bearing its capacity.

Static Axial Load Rating: 93 kN against a Dynamic Axial Load Rating of 35 kN. The static figure sitting well above the dynamic one is normal for a thrust ball bearing: the whole ball complement shares a stationary axial load, while the dynamic rating is limited by fatigue life under rotation.

Limiting Speed: 2,800 rpm on grease and 4,300 rpm on oil. A thrust ball bearing turns more slowly than a radial one of the same bore because centrifugal load pushes the balls outward against the raceway lip.

Shaft Washer Outside Diameter (d1): 78 mm. Housing Washer Bore (D1): 57 mm. The 2 mm difference between the two bores is what lets the housing washer float clear of the shaft.

Mounting data

Shaft Abutment Diameter (da min): 69 mm. Housing Abutment Diameter (Da max): 64 mm. Maximum Abutment Fillet Radius (ra max): 0.6 mm. Bearing Chamfer (r min): 0.6 mm. Seat Type: Flat.

Quantity and configuration

Unit Quantity: 1 Pc. One complete bearing — shaft washer, housing washer and ball-and-cage assembly.

Interchange guidance

51111 is an ISO designation and the 55 x 78 x 16 mm envelope is shared across makers, so 51111 from any manufacturer occupies the same seats. The equivalent double-direction bearing on the same bore is a 52000-series number and is a different height, which makes it a related size rather than a swap. A 51211 shares the bore but is a heavier section at 78 mm outside diameter.

Searchable variants of the part number: 51111, 51-111, 51 111.