How to select the right precision crossed roller bearing size

Selecting the right precision crossed roller bearing size involves considering several key factors to ensure optimal performance in your application.

Precision Crossed Roller Bearing Size Selection Guide

1. Determine Load Requirements

Radial Load (Fr): The force perpendicular to the shaft.

Axial Load (Fa): The force parallel to the shaft.

Moment Load (M): The tilting or overturning force.

Crossed roller bearings handle combined loads (radial, axial, and moment) efficiently. Calculate the expected loads and refer to the bearing’s dynamic (Cr) and static (Cor) load ratings.

2. Consider Bearing Dimensions

Inner Diameter (ID): Match the shaft size.

Outer Diameter (OD): Ensure it fits within the housing.

Width (Height): Check space constraints.

Standard sizes range from small (e.g., 10mm ID) to large (e.g., 500mm ID).

3. Check Rotational Accuracy & Rigidity

Precision bearings (e.g., ABEC-5, ABEC-7, P4, P2) have tighter tolerances.

For high rigidity, select a bearing with preload (eliminates internal clearance).

4. Speed Requirements

Check the limiting speed (rpm) based on lubrication and cage material.

Polyamide cages allow higher speeds than steel cages.

5. Mounting Configuration

Inner/Outer Ring Rotation: Decide if the inner or outer ring rotates.

Split vs. Non-Split Design: Split types (e.g., XR series) are easier to install.

6. Environmental Conditions

Lubrication: Grease (standard) or oil (high-speed).

Sealing: Optional seals for dust/moisture protection.

Material: Stainless steel (corrosion resistance) or standard chrome steel.

7. Bearing Series Selection

Common precision crossed roller bearing series:

RB / RA (Standard)

XR (Split Inner Ring)

CRBH (Thin-Type)

RU (Non-Split)

RE / SX (High Rigidity)

8. Consult Manufacturer’s Catalog

Compare load ratings, dimensions, and tolerances (e.g., IKO, THK, NSK, Schaeffler).

Use life calculation formulas (e.g., ISO 281) for expected bearing life.

Example Selection Process:

Application: Rotary table for CNC machine.

Loads: Fr = 2000 N, Fa = 1500 N, M = 100 Nm.

Shaft Size: 50mm → ID = 50mm.

Precision Needed: ABEC-7 (P4).

Speed: 300 rpm → Standard grease lubrication OK.

Choice: RB5008 (50mm ID, 80mm OD, 15mm Width) or XR305 (50mm ID, 80mm OD, Split Design).

Final Tips:

If unsure, consult a bearing supplier with load & speed data.

Consider custom sizes for unique applications.

Ensure proper installation alignment to maximize bearing life.

By following these steps systematically, you can confidently select the right precision crossed roller bearing size for your application's specific needs.