Fareed Mohmed · Engineering
Bearing Arrangement Selector
Locate · Support · Accommodate
Pick your shaft scenario and get the recommended bearing arrangement — which bearing locates the shaft, whether a paired angular-contact mounting is worth it, and why — with schematic diagrams for each option.
Find Arrangement by Scenario
All Arrangements
Fixed – Floating (Locating / Non-Locating)
The locating bearing is fixed axially in its housing and takes all the axial (thrust) load plus the radial load. The non-locating bearing carries radial load only and is free to shift slightly in its housing — typically via a clearance fit on the outer ring or a sliding bearing type — so the shaft can grow with temperature without the two bearings fighting each other.
Two Locating Bearings (Adjusted or Fixed)
Both bearings are axially fixed in their housings, sharing the axial load between them (in different load directions) with a small designed-in axial clearance or a light preload. Only appropriate on shafts short enough, or cool enough, that thermal expansion between the two fixed points won't build up damaging internal stress.
Paired Angular Contact — Back-to-Back (DB)
The two bearings' backs sit together, fronts facing outward. This spreads the effective support points as wide as possible, giving the pair the highest resistance to shaft tilt (moment load) of the three pair arrangements — the standard choice for precision spindles and machine tool axes.
Paired Angular Contact — Face-to-Face (DF)
The two bearings' fronts sit together, backs facing outward. The narrower effective base gives less moment stiffness than back-to-back, but the geometry is more forgiving of small shaft deflection or housing misalignment — useful where DB's rigidity would otherwise over-stress the bearings under a slightly misaligned mount.
Paired Angular Contact — Tandem (DT)
Both bearings are oriented identically, so their axial capacity stacks in a single direction rather than being split between two directions. Used when the axial load is heavy but genuinely one-directional — tandem pairs are also often combined with a third bearing (DBT/DFT) to add capacity in the opposite direction too.
Quick-Scan Table
| Shaft Scenario | Recommended Arrangement |
|---|---|
| General-purpose motor, pump or fan shaft | Fixed – Floating (Locating / Non-Locating) |
| Long shaft with significant thermal expansion (kiln, long conveyor) | Fixed – Floating (Locating / Non-Locating) |
| Gearbox shaft, moderate length, combined radial and axial load | Fixed – Floating (Locating / Non-Locating) |
| Short, rigid, cool-running shaft needing precise axial position both ways | Two Locating Bearings (Adjusted or Fixed) |
| Small precision mechanism, low thermal growth, controlled end-float | Two Locating Bearings (Adjusted or Fixed) |
| Precision spindle or machine tool axis needing maximum stiffness | Paired Angular Contact — Back-to-Back (DB) |
| Shaft needing high positioning accuracy and resistance to tilt under load | Paired Angular Contact — Back-to-Back (DB) |
| Precision shaft where some housing misalignment or shaft deflection is expected | Paired Angular Contact — Face-to-Face (DF) |
| Heavy axial (thrust) load in one direction only — e.g. an unbalanced pump thrust | Paired Angular Contact — Tandem (DT) |
Explanatory Notes
Every shaft needs exactly one axial "anchor point"
Somewhere on the shaft, something has to fix its axial position — otherwise the shaft can wander back and forth under any axial load. Fixed-floating gives that job to one bearing; two-locating and the paired arrangements share it between two bearings (or two rings of the same pair) instead. What must never happen is two independent axial anchors fighting each other with no planned clearance between them.
Thermal growth is the reason "floating" exists at all
A steel shaft grows several tenths of a millimetre per metre for every 100°C rise. If both ends were rigidly fixed axially with no float anywhere, that growth would have nowhere to go and would load the bearings internally as if someone had pre-loaded them on purpose — except uncontrolled and getting worse as the machine warms up. The floating bearing (or the small planned gap in a two-locating arrangement) is what absorbs that growth.
DB vs. DF is a stiffness-vs-tolerance trade-off, not a strength difference
Both back-to-back and face-to-face pairs use the same two bearings and carry similar load ratings — the difference is in how well the resulting pair resists the shaft trying to tilt under an off-axis load. Back-to-back's wider effective base resists tilt much better, which is why it's the default for anything needing positioning accuracy; face-to-face trades some of that away for tolerance to shaft deflection or a less-than-perfect housing bore.
Related tools
To first identify which bearing type suits the application, see the Bearing Type Selector. For the shaft and housing fit once an arrangement is chosen, see the Shaft & Housing Fit Calculator. To verify load and life, see the Bearing Load, Life & Static Capacity Calculator.