SKF61860-MAOpen Thin-Section Deep Groove Ball Bearing 300 x 380 x 38 mm, Machined Brass Cage, 618 Series, 1 Pc

Product Description

What this part is

A single-row deep groove ball bearing in the 618 large-bore thin-section series — 300 mm bore, 380 mm outside diameter, 38 mm wide, open on both sides, with a machined brass cage. Deep groove ball bearings carry radial load plus axial load in either direction. At this size the bearing is normally used as the rotating support in ring-shaped assemblies: rotary tables and indexers, swivel and slew joints, filling and capping heads, textile and paper rolls, and large fan and blower hubs.

Decoding the designation

6 – single-row deep groove ball bearing18 – dimension series 618, the very slim section and narrow width for the bore60 – bore code, 60 x 5 = 300 mm boreMA – machined brass cage, outer-ring centred (M is the machined brass cage, A the outer-ring guidance)No closure suffix – open both sides; a 2Z would be metal shields and a 2RS1 rubber contact sealsNo clearance suffix – normal (CN) radial internal clearance

What these specs mean in practice

The 618 series is the thinnest standard deep groove section made. Only 40 mm of radial wall each side carries a 300 mm shaft, and the bearing is just 38 mm wide. That buys two things a standard series cannot: it passes a very large or hollow shaft through a compact housing, and it saves a great deal of weight and rotating inertia in a large-diameter assembly. What it costs is load capacity and stiffness — the ball complement is small for the diameter and the rings are slender, so the bearing is chosen for guidance and moderate load, not for heavy radial duty.

The machined brass cage is the other reason to choose this part. A one-piece machined brass cage is far more tolerant of high speed, misalignment, marginal lubrication and elevated temperature than a pressed steel or polyamide cage, and it has no plastic temperature ceiling. It is also heavier and costlier, which is exactly why it shows up on large, expensive, hard-duty bearings like this one.

Being open, the bearing arrives without service grease. It must be lubricated on assembly and sealed by the housing, and it is not a substitute for a shielded or sealed variant that arrives pre-greased and closed. In return it relubricates freely and will run in circulating or mist oil.

Published specifications

Bore: 300 mmOutside diameter: 380 mmWidth: 38 mmRadial section wall: 40 mm each sideDimension series: 618 (large-bore thin section)Rows: 1Closure: open, both sidesInternal clearance: normal (CN)Cage: machined brass, outer-ring centredMaterial: through-hardened bearing steelEAN: 7316577093677

Quantity and configuration

Sold as 1 piece, one open bearing. No shields, no seals, no snap ring, no housing.

Fitting notes

Slender rings take the shape of whatever they are mounted in, so at this diameter shaft and housing roundness matter more than the bearing tolerance does. Support the ring being fitted across its full face, press only on that ring, and never let mounting force cross the balls. Heat mounting to about 80 to 100 °C is the usual method at 300 mm bore. Fill roughly a third of the free internal space with a grease rated for the running speed, and provide housing sealing — the bearing has none of its own.

Interchange guidance

Same-envelope genuine interchanges are 300 x 380 x 38 mm 618-series bearings with a machined brass cage: FAG 61860-M, NSK 61860MA and NTN 61860. A 61860 with a pressed steel cage, a 61860 MA C3 (greater clearance) or a sealed 61860-2RS1 are related parts with different cage, clearance or closure — not drop-in equivalents. A 6060 or 16060 of the same bore is a different section entirely.