What Bearing Is Recommended for Pillow Blocks? Insert Bearing Selection Guide
Which bearings are used in each type of pillow block, how to select them, and when it is convenient to replace only the insert.
The UC Insert: The Standard for Compact Pillow Block Bearings
In compact pillow block bearings (UCP, UCF, UCFL), the bearing is a UC-type insert: a ball bearing with two characteristics that distinguish it from a standard bearing. First, the outer ring has a convex spherical surface that fits into the spherical housing seat and enables mounting self-alignment. Second, the inner ring is extended on both sides and incorporates the shaft locking mechanism (set screw or collar). The typical steel is 52100, and the balls run in a steel or polymer cage.
Insert Variants According to Fixation Type
Set Screw (UC): the most common; two set screws at 120° or 90° secure the insert to the shaft. Economical and sufficient for most loads. Eccentric Collar (UEL/SB with suffix): a collar that wedges by rotating in the direction of rotation. Concentric Locking Collar: designs such as Sealmaster SKWEZLOC or Dodge D-Lok, providing near-perfect concentricity and reduced fretting corrosion; preferred in applications with vibration or where smooth operation is important. Adapter Sleeve: used for larger inserts and pedestal bearings.
Bearings for Pedestal Pillow Blocks
In pedestal pillow blocks, the bearing has a higher load capacity: double-row spherical roller bearings (with the highest combined load capacity and true self-alignment, even dynamically, for heavy shafts with deflection), or tapered roller bearings for high combined radial and axial loads. In floating configurations, cylindrical roller bearings are used, allowing the internal axial displacement required to absorb thermal expansion. These bearings are often mounted on an adapter sleeve, which allows field adjustment of internal clearance.
How to Select the Correct Insert
Cinco criterios: bore (debe coincidir exactamente con el diámetro del eje — no negociable); tipo de fijación (prisionero, collar excéntrico, concéntrico o manguito según vibración y precisión); serie (2 normal, 3 mayor capacidad para el mismo bore); sellado (estándar, doble labio, triple labio según entorno); y material (acero 52100 estándar, inoxidable o recubierto para corrosión/alimentos). Importante: el inserto debe ser compatible con la carcasa — un inserto serie 300 no entra en una carcasa serie 200.
When to Replace Only the Insert?
When the Housing Is Still in Good Condition (no cracks, with the spherical seat intact and mounting holes in good condition), but the bearing has failed (noise, play, grease with metallic particles). Replacing only the insert saves cost and time. Order the insert code (for example, UC205) instead of the complete unit (UCP205). If the housing is damaged or corroded, replace the complete pillow block unit.
The bearing in a pillow block is the UC insert (self-aligning ball bearing with a spherical outer ring) in compact units, or a spherical/cylindrical roller bearing in pedestal units. Understanding this distinction allows you to replace only the damaged component, specify the correct part, and ensure compatibility with the housing. At BIOSA MOTION TECHNOLOGIES, we have UC inserts in all sizes and pedestal bearings from Dodge, Timken, Regal Rexnord, and GABB IP.