Radial vs axial load: which bearing takes which
Before you pick a bearing, you have to know which way the load pushes. Get the direction wrong and no amount of size or quality saves it — a thrust bearing in a radial job fails immediately. The two directions, and which bearings answer them:
The two directions
- Radial load acts at right angles to the shaft — the weight of a wheel, the pull of a belt, the load on a gear. The bearing carries it across its diameter.
- Axial (thrust) load acts along the shaft — the push down a drive screw, the thrust of a fan or pump impeller, the end-load on a helical gear. The bearing carries it along its axis.
- Combined load is both at once, which is the real-world norm for most shafts.
Which bearing for which load
| Bearing | Radial | Axial |
|---|---|---|
| Deep groove ball | Good | Moderate, either direction |
| Cylindrical roller | Very high | Little to none (most types) |
| Needle roller | High (thin section) | None |
| Angular contact ball | Good | High, one direction |
| Tapered roller | High | High, one direction |
| Spherical roller | Very high | Moderate |
| Thrust ball | None | High, one direction only |
The all-rounder: deep groove ball
A deep groove ball bearing takes radial load and a fair amount of axial load in either direction, which is why it is the default for general machinery — it copes with combined loads without any special arrangement. That versatility is a big part of why a 6204 and its family are the most common bearings there are.
Heavy thrust: one direction, so use a pair
Angular contact and tapered bearings carry heavy thrust — but only one way. Load them the other way and they come apart. Because most shafts see thrust both ways, these are mounted in opposed pairs so that between them they hold thrust in both directions, often with a preload. That is the whole logic behind DB/DF/DT arrangements and preload.
Pure thrust: no radial load at all
A thrust ball bearing is built only for axial load — its washers face each other across the balls with nothing to locate the shaft radially. Put a radial load on it and it has no way to carry it. So even where the thrust figures look right, a thrust bearing cannot stand in for a radial one, and usually works alongside a separate radial bearing that takes the sideways load.
Choosing, in one line
Pure radial and heavy → cylindrical or spherical roller. Radial with some thrust → deep groove ball. Heavy combined → tapered or angular contact, in a pair. Pure thrust → thrust bearing, with a radial bearing to help. The full type walk-through is in ball vs roller: which bearing type.
General engineering reference only. Load capacity in each direction is specific to the bearing — confirm the figures in the manufacturer's catalogue.