What Are the Types of Crossed Roller Bearings

The types of crossed roller bearings are defined by three things: how the rings are built, how the bearing is sealed, and how accurately it runs. Integrated and separated rings change how the bearing mounts. Open and sealed designs change how it survives the environment. P5, P4, and P2 grades change how precisely it rotates. This guide works through each type so you can match the bearing to the machine.

1Types by Ring Construction

The biggest split among the types of crossed roller bearings is between integrated and separated ring designs. This choice changes how the bearing mounts and how it handles load.

Integrated Ring (RAU Series)

An integrated ring crossed roller bearing is machined from a single piece for each ring. The inner ring is one solid part, and the outer ring is one solid part. Nothing bolts together, so there is no joint to loosen or shift.

The one-piece rings hold the rollers in a fixed, factory-set relationship. That gives the bearing its stiffness and keeps runout low. Yuanhe builds the RAU series this way, with preload set at the factory so the bearing arrives ready to mount.

Separated Ring

A separated ring design bolts the outer ring together from two pieces. This style is easier to assemble around a shaft or housing because you can open the ring. The tradeoff is that a bolted joint needs more care during mounting to hold the preload and alignment.

Separated rings show up on large bearings where sliding a one-piece ring over a shaft is impractical. They also let a machine be serviced without tearing down the whole assembly. The cost is a small penalty in stiffness and the need for careful bolt tightening.

2Types by Sealing

The second split is sealing. It decides how well the bearing resists contamination and how long the grease stays inside.

Open Type

An open bearing has no seals, so it runs with the lowest friction and the highest speed. It belongs in a clean, enclosed housing where the lubricant is supplied and the environment stays free of dust. Machine tool spindles and clean rotary tables often use open bearings.

The open type also runs coolest, because nothing drags against the rings. That matters in high-speed spindles where friction heat is the limiting factor. The tradeoff is simple: the housing must supply the protection the bearing lacks.

Sealed Type

A sealed bearing carries contact seals that keep dust and moisture out and grease in. It is the right choice for robot joints and medical equipment that run in normal air and cannot be re-greased easily. The seal adds a little friction, but the protected grease pays it back in longer life.

Sealed types dominate in robot arms and semiconductor handling, where the environment is dusty or the machine must run for years without service. The lubrication guide explains how the sealed grease supply works over time.

3Types by Accuracy Grade

Accuracy grade is the third way to sort these bearings. The grade sets the runout and rotational accuracy, and it drives both performance and cost.

The common grades are P5, P4, and P2, where P2 is the tightest. General motion and standard rotary tables use P5. Precision stages, metrology, and semiconductor handling move up to P4. The tightest P2 grade serves applications where a few microns of wobble ruin the result. A full breakdown of what each grade means is in the accuracy grades guide.

Higher grades cost more because they demand tighter manufacturing control. The right grade is the lowest one that meets the runout budget. Paying for P2 on a conveyor is waste, and using P5 on a wafer stage invites rejects.

4Matching the Type to the Job

The table below lines up each combination of construction and sealing with the kind of machine it serves.

5How to Pick

Start with three questions. How does it mount? How clean is the environment? How tight must the rotation be? The answers point straight to a type.

For a robot joint, pick an integrated, sealed bearing with the preload set at the factory. For a machine tool table in an oiled enclosure, an open integrated bearing runs fastest. For a large ring that must mount in place, a separated design is easier to install. The full selection guide works through each variable in detail, and the preload guide explains why factory-set preload matters.

6Size Range and Series Naming

Crossed roller bearings come in a spread of bore sizes, from compact units for small robot wrists up to large rings for heavy rotary tables. The bore and outside diameter set the envelope, and the width sets how much load the bearing carries.

The RAU series name identifies the integrated ring family as one series, not a split between separate parts. When you specify an RAU bearing, you are asking for the one-piece ring design with factory-set preload. The size within the series then follows the standard bore and outside diameter you need for the shaft and housing.

Confirming the size is straightforward. Measure the shaft diameter, the housing bore, and the available width, then match those three numbers to the bearing. The load rating tells you whether the size is strong enough for the duty.

7Material and Finish Options

Standard crossed roller bearings use GCr15 chromium bearing steel for the rings and rollers. The steel is hardened and ground to a fine finish on the raceways. A smooth raceway means low friction and long life, because roughness on the track wears the rollers faster.

For cleanrooms, food processing, or humid environments, stainless steel is the better material. It resists corrosion and stands up to washdown. The load rating dips slightly compared to chromium steel, so stainless is a decision driven by the environment rather than the load alone.

Coatings and special finishes are available for demanding cases. Thin dense chrome and other surface treatments protect the rings where corrosion and wear overlap. These options are specified case by case, and the supplier can recommend the right finish once the operating conditions are known.

8Examples by Application

A few concrete cases make the types easier to picture. A small six-axis robot wrist uses an integrated, sealed bearing with P5 accuracy, because it needs stiffness in a tiny envelope and runs in a factory. A semiconductor wafer stage uses an integrated, open or sealed bearing at P4 or P2, because a few microns of runout scrap a wafer.

A large rotary table on a machining center often uses an open integrated bearing running in an oil bath, where speed and stiffness matter more than dust protection. A heavy gantry on a medical scanner uses a sealed bearing so it runs for years without service. The pattern is consistent: match the type to the environment and the accuracy budget.

9Frequently Asked Questions

Not sure which type fits your machine? Tell us your load and mounting, and we will match the bearing.