Double row cylindrical roller bearings 2

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Double Row Cylindrical Roller Bearings

Double row cylindrical roller bearings handle heavier loads with double row cylindrical rollers than single-row designs while maintaining compact dimensions and excellent running accuracy.

ZMS is a professional supplier of double row cylindrical roller bearings in China. We can fast quote within 12 hours with detail stocking or delivery information. Our bearings are character with high precision P5 and P4 for machine tools and so on high accuracy applications. Brass cage are standard option. While full-complement (no cage) for maximum load in low-speed applications.

We can supply series following:
· NN Series: Ribs on the inner ring (separable outer ring).
· NNU Series: Ribs on the outer ring (separable inner ring).
· Available with cylindrical bore or tapered bore (K suffix) for easy adapter sleeve mounting.

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Why us?

Manufactured from premium chrome steel or special alloys with optimized heat treatment.
Precision-ground raceways and rollers for smooth, quiet operation.
Alternative with major brands (SKF, NSK, NTN, Timken, FAG, etc.).
Competitive pricing with much considerable times and full technical support.
Custom made can be acceptable
Wooden case packing or special packing as request

Specifications

Bore Diameter (d): 25 mm to 750 mm (or larger on request)
Outside Diameter (D): Up to 1000 mm+
Width (B): Varies by series
Load Ratings: Significantly higher radial dynamic and static loads compared to single-row equivalents
Clearance: CN (normal), C3, C4, or customized
Speed Ratings: High limiting speeds depending on lubrication and precision class
Operating Temperature: Up to +150°C (standard) or higher with special materials

Applications

Machine tool spindles (lathes, milling machines, grinding)
Gearboxes and speed reducers
Rolling mills and heavy machinery
Printing equipment
Pinion stands and large electric motors
Construction and mining equipment

NN vs. NNU Design Structures

When selecting double row cylindrical roller bearings, understanding the rib (flange) configuration is crucial for your shaft design.

NN Series: Features three integral ribs on the inner ring and a smooth, ribless outer ring.
NNU Series: Features three integral ribs on the outer ring and a smooth, ribless inner ring.

The Engineering Advantage: Both designs allow for relative axial displacement between the shaft and the housing entirely within the bearing itself. This makes them the ideal choice as non-locating (floating) bearings. During high-speed operations, they effectively accommodate the thermal expansion of the shaft without inducing any harmful internal axial stress, ensuring smooth and continuous performance.

The Advantage of Tapered Bores (K Suffix)

A defining feature of our precision double row cylindrical roller bearings is the tapered bore option, easily identified by the “K” suffix (featuring a standard 1:12 taper ratio).

Why is this essential for high-end machinery? By mechanically driving the tapered bore bearing up a tapered shaft seat, engineers gain total control over the bearing’s internal geometry. You can perfectly adjust the radial internal clearance or even apply a highly precise negative clearance (preload). This eliminates all play and ensures ultimate spindle rigidity, which is mandatory for achieving flawless surface finishes in CNC machining.

Super Precision Standards for Machine Tool Spindles

For machine tool spindles and high-speed milling equipment, standard industrial tolerances are simply not enough. ZMS manufactures these bearings in SP (Super Precision) and UP (Ultra Precision) tolerance classes, guaranteeing micrometer-level runout accuracy.

To further withstand the severe vibrations and dynamic forces of high-speed heavy cutting, our super precision bearings are equipped with robust, machined brass cages (M suffix) or lightweight Polyamide cages. This combination ensures stable roller guidance, excellent heat dissipation, and prolonged spindle life under the most demanding radial loads.

For a complete spindle solution, pair our NN series bearings with ZMS Super Precision Angular Contact Ball Bearings to manage your axial thrust loads

Frequently Asked Question

Can double row cylindrical roller bearings take axial loads?

No. These bearings are designed to carry massive radial loads only. They allow for axial displacement. In a machine tool spindle, they must be paired with angular contact ball bearings or thrust bearings to handle the axial forces.

What does the “K” mean in an NN3020K bearing?

The “K” suffix indicates that the bearing has a tapered bore (typically a 1:12 taper) rather than a standard straight cylindrical bore. This allows for extremely precise adjustment of the radial internal clearance during installation.

Why use a double row cylindrical bearing instead of a single row?

The double row design incorporates more, slightly shorter rollers. This significantly increases the radial load capacity and, more importantly, drastically improves the radial stiffness/rigidity, which is critical for CNC machining accuracy.