Mounted Ball Bearings
Ball bearing units mounted in a housing (pillow block, flange, take-up, and hanger styles) — bolt directly into a frame or bracket. For the bare, unmounted insert alone, see Ball Bearings.
A mounted ball bearing is a complete unit: a ball bearing insert pre-assembled into a cast, pressed or molded housing that bolts directly to the machine frame. Because the bearing arrives seated in its housing, there is no press fit to arrange and no separate housing to bore, which is why these units dominate conveyors, fans, agricultural equipment and material handling generally. The insert's outer ring is spherical and sits in a matching seat, so the unit takes up the shaft misalignment left by ordinary fabrication.
Also known as: mounted bearings, mounted unit bearings, mounted ball bearing units, material handling bearings
Series in this category
Related guides: Pillow block bearing sizes, Bearing selection guide, Bearing lubrication basics, Cross-reference help
| Specification | What it means |
|---|---|
| Shaft size | The bore of the insert and so the shaft diameter the unit mounts on. The first thing to fix when replacing a unit. |
| Housing style | Pillow block, flange, take-up or cartridge — the form that decides how and where the unit bolts on. |
| Locking type | How the insert grips the shaft: setscrew, eccentric collar, concentric collar or adapter sleeve. |
| Base to center height | The distance from the mounting face to the shaft axis, which sets where the shaft sits relative to the frame. |
| Bolt hole spacing | The centers of the mounting holes. It must match the existing frame for a drop-in replacement. |
| Seal type | The arrangement keeping contamination out and grease in, which usually decides service life in dirty duty. |
The insert is the bearing itself, with a spherical outer ring and a means of locking to the shaft. A mounted bearing is that insert already fitted into a housing. If the housing on the machine is sound, only the insert usually needs replacing.
They accommodate misalignment present at installation, because the spherical outer ring can swivel in its seat as the unit is bolted down. That is static accommodation for frames that are not perfectly true; it is not a bearing designed to follow a shaft that deflects continuously in service.
When the shaft always turns the same way and the load is heavier or less steady than setscrews hold well. The collar cams against the shaft in the direction of rotation, so it tightens in service, but that same behavior is why it is the wrong choice on a reversing drive.
Many have a grease fitting and are designed to be relubricated on an interval; others are sealed for life and are meant to be replaced instead. Which one is in front of you matters, because re-greasing on a schedule is the cheapest life extension available on this kind of bearing.
