What are Double Row Thin Section Bearings?

Double row thin section ball bearings, also called thin cross-section double row angular contact ball bearings, pack two rows of balls into a deliberately slim ring set. What defines a thin section bearing is that the wall between the bore and the outer rim stays small and roughly constant as the bore grows, so the bearing adds very little diameter and weight for a given shaft. In short, they deliver the capability of a double row angular contact bearing in a cross-section that barely intrudes on the space around the shaft, which is exactly why they exist as a category of their own.

Accu carries the double row angular contact type, with the two rows set at opposing contact angles, so a single slim unit carries radial load together with axial thrust in both directions and resists the tilting moments that a thin bearing might otherwise struggle with. 

How Double Row Thin Section Bearings Work

A double row thin section ball bearing works in the same way as a standard double row angular contact bearing, sharing the radial load across two rows of balls while the angled contact lines take thrust in either direction and hold the shaft against tilting. The difference is in the rings. By keeping the radial section thin, the bearing trades a measure of outright load capacity for a dramatic saving in size and weight and it frees up a large bore for the diameter it occupies. That large bore is often the whole point, since it leaves room to pass a shaft, cabling, fluid or an optical path straight through the centre of the bearing.

Picture the rotary joint of a lightweight robot arm. The joint needs to turn smoothly under the weight and reach of the arm, resist the bending moment that reach creates and still leave a clear channel down the middle for the power and signal cables feeding the tools further along the arm. A double row thin section ball bearing suits this perfectly: its large bore carries the cabling, its double row angular contact design reacts the combined radial, axial and tilting loads at the joint and its slim cross-section keeps the arm light and compact so the motors are not fighting the weight of the bearings themselves. The same logic drives their use in gimbals, rotary tables, scanning equipment and aerospace actuators.

Materials Double Row Thin Section Bearings Are Made From

A single bearing steel runs through the thin section range, picked for fatigue strength in a slim wall.

• Steel - (AISI 52100): A high-carbon chromium bearing steel, hardened so the slim section still returns a long fatigue life.

Sizes and Types of Double Row Thin Section Bearings Available

Accu's double row thin section ball bearings run through the 3800 series, covering a wide spread of bores while holding the cross-section slim throughout.

• Inside diameters: from 10 mm to 70 mm
• Outside diameters: from 19 mm to 90 mm
• Radial cross-section: as little as 4.5 mm of material between bore and rim and only 10 mm even at the 70 mm bore

The bearings are supplied in a single Steel - (AISI 52100) grade and in their natural finish, with no additional coating or plating applied. It’s the slim section that sets these apart from the standard double row range: a 70 mm bore bearing measures just 90 mm across, where a conventional bearing of that bore would be considerably larger and heavier.

Three closure options cover the range of working conditions.

• Open: open on both sides for maximum speed and the lowest running friction.
• Double Shield (2Z): metal shields on both sides that keep larger debris out while allowing higher speeds and low drag.
• Double Seal (2RS): rubber seals on both sides that retain grease and exclude dust and moisture, for dirty or exposed positions.

The open and shielded options are offered across the smaller and mid-range bores, while the largest sizes are supplied sealed.

FAQs

Q: What is a thin section bearing useful for?

A: Thin section bearings are used wherever a design needs a large bore but very little room around it and where saving weight matters. Because the cross-section stays slim as the bore grows, the bearing adds minimal diameter and mass, which is why thin section double row ball bearings suit robotics, rotary tables, optical and medical scanning equipment, aerospace actuators and any hollow-shaft assembly that has to route cables, fluid or light through its centre. 

They deliver the combined load capacity of a double row angular contact bearing in a package that barely intrudes on the surrounding structure.

Q: What is the difference between single row and double row bearings?

A: A single row bearing has one row of balls and handles radial load with limited axial capacity. A double row bearing adds a second row, which raises the load capacity and, in the angular contact form used here, lets the bearing take thrust in both directions and resist tilting moments in one position. In a thin section double row bearing you get that double row behaviour while keeping the cross-section slim, so the extra capability does not come at the usual cost in size or weight.

Q: What is the difference between 2RS and ZZ bearings?

A: 2RS and ZZ describe how the bearing is closed. 2RS means two rubber contact seals that grip the inner ring to retain grease and keep out dust and moisture, at the cost of a little more friction. ZZ, also written 2Z, means two metal shields that sit close to the inner ring without touching it, keeping larger debris out while allowing higher speed and lower drag. 

Accu's thin section double row ball bearings are offered open for maximum speed, 2Z shielded for light protection and 2RS sealed for dirty or exposed conditions.

Q: How do you identify a thin section bearing?

A: The giveaway is the cross-section. Compare the bore to the outside diameter: on a thin section bearing the gap between the two is small and stays roughly constant as the bore increases, so even a large bearing can have surprisingly little material in its walls. 

Accu carries a 3800-series code with a suffix for the closure, 2Z for shielded and 2RS for sealed and the part number reads as bore and outside diameter, so 3806-B is 30 mm x 42 mm. If the ring looks slim for its diameter and the two figures in the size sit close together, it is a thin section bearing.

Bespoke Double Row Thin Section Ball Bearings Manufacture.

High precision, bespoke manufacture of Double Row Thin Section Ball Bearings to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.