32321 bearing: complete specifications & equivalents
The 32321 is a ISO 355 radial bearing sized 105 x 225 x 81.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Bore diameter d | 105 mm |
| Outer diameter D | 225 mm |
| Width B | 81.5 mm |
| Seal / shield | open |
| Internal clearance | CN available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Operating temperature | -30 to +120 °C |
| Mass (geometry estimate) | 12934 g |
| Standard | ISO 355 |
| Catalog version | iso355-geometry |
| Last verified | 2026-09-24 |
Source: ISO 15 boundary-dimensions standard · extracted 2026-09-24
Standard-interchange bearing: dimensions per ISO 15; CN clearance, P0 tolerance and a stamped-steel cage are catalogue defaults unless the supplier states otherwise, and mass is a geometry-derived estimate. Brand catalogue load ratings and limiting speeds for 32321 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & 32300-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 8.858 in |
| Width B | 3.209 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 60 mm |
| Smallest bore in 32300-series | 20 mm |
| Largest outer diameter in 32300-series | 240 mm |
| Width range across 32300-series | 22.25–84.5 mm |
| Bore position in 32300-series (smallest first) | 18 of 19 |
| Bore above smallest 32300-series size | 85 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 32321 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 32321 model number is decoded
In the 32300-series the last two digits of 32321 encode the bore: code 21 = 105 mm (code × 5 from 04 upward). The ISO 355 envelope is 225 mm outside diameter and 81.5 mm total assembly width T over the separable cone and cup — 4.134 × 8.858 × 3.209 in, with a 60.0 mm radial section height. Tapered rollers carry combined radial and single-direction axial load; bidirectional thrust needs an opposed pair (X face-to-face or O back-to-back) adjusted at fit-up. With a rotating cone on a 105 mm shaft, typical catalogue practice is a m6 shaft seat with an H7 housing bore, EP lubrication and a defined end-play setting — verify against the load direction and magnitude.
Typical equipment & failure modes
Common applications
- crane travel wheels and winch drums
- railway axle boxes
- agricultural tractor axles
- truck and trailer wheel hubs
- heavy final drives and differentials
Known failure patterns
- fretting corrosion on a loose shaft seat when the cone is pressed to an interference that relaxes with wear
- cup creep and housing bore fretting when the outer ring is left without its specified press fit
- roller large-end smearing and scoring against the inner-ring guide rib from loss of the EP lubricant film
- raceway spalling at the roller-rib junction after the L10 life or sustained axial overload
- over-preload heat: a shim stack cut too thin drives contact stress up and seizes the cone on the seat
Selection pitfalls — read before you substitute
- The large 105 mm-bore 32321 develops substantial mounting forces; heat the cone (induction heater, max 120 °C) and never tighten the adjusting nut to seat it — draw it up by torque, then back off to the mark, leaving roughly 0.05–0.20 mm end play on the 105 mm shaft.
- The 323 heavy wide series at 105 mm bore (225×81.5 mm) is a steep-angle, high-thrust row for heavy final drives; its 60.0 mm section and 81.5 mm width dwarf the 30221, and its speed ceiling is the lowest of the four series.
- The 81.5 mm-wide 32321 ring seats against a shaft and housing shoulder whose fillet must clear the bearing chamfer: keep the corner radius small enough that the 105 mm bore and 225 mm cup seat square — an undercut beats an oversized radius, which lifts the ring and edge-loads the 60.0 mm section.
- When mounting 32321 to a 105 mm shaft, warm the cone to 80–100 °C and slide it dry to the shoulder; cooling shrinks it into its interference, whereas hammering a cold cone through a 225 mm assembly dents the tapered raceway before first run.
- Relubrication for 32321 must reach the rib-roller end contact, not just the 105 mm bore; in a hub repack, work EP grease through the roller set until it exudes at both faces of the 81.5 mm-wide assembly or the sliding rib contact starves first.
- A single 32321 takes thrust in ONE direction — the rollers roll toward the rib under load, so reverse thrust unloads the contact. For a wheel or pinion use an opposing 323-series pair adjusted against each other.
- The cone and the cup of 32321 are separable: order and fit them as a matched set; never mix a cone from one manufacturer with another brand's cup — roller geometry and contact angle are not identical across brands.
Frequently asked questions
What are the dimensions of a 32321 tapered roller bearing?
A 32321 single-row metric tapered roller bearing per ISO 355 has a 105 mm bore, 225 mm outer diameter and 81.5 mm total assembly width (4.134 × 8.858 × 3.209 in), a 60.0 mm radial section and roughly 12934 g geometry-based estimated mass; catalogue masses vary with roller and cage design.
How does the 32321 bore code work?
The last two digits of 32321 are bore code 21, giving 21 × 5 = 105 mm bore — the same convention as 6xx ball bearings, starting at code 04 (20 mm). The 225 mm OD and 81.5 mm width come from the ISO 355 diameter and width series, not the bore code alone.
What is the cone and cup of 32321?
Tapered roller bearings are separable: the cone is the inner ring with the tapered rollers and cage, the cup is the outer ring. 32321 denotes a matched cone-and-cup set. They are fitted separately — cone pressed on the shaft, cup in the housing — and adjusted against each other.
How is the preload or clearance of 32321 set?
At fit-up the 105 mm-bore cone is tightened against the cup while the hub is rotated, seated, then backed off to the specified end play — a typical starting range of 0.05–0.20 mm for a 105 mm bore — and locked with shims, a locknut or a spacer. Too tight overheats and seizes the rib; too loose causes skid, noise and early wear. Confirm the exact figure in the hub or axle-maker procedure.
Can 32321 take axial load in both directions?
A single 32321 takes thrust in one direction only — the roller large ends bear against the inner-ring rib under load. Bidirectional axial load requires an opposed pair: X (face-to-face) tolerates misalignment slightly better, O (back-to-back) gives a wider load centre and more moment stiffness.
Reviewed & verified by the MPN Base engineering desk against source catalog iso355-geometry on 2026-09-24. Read our editorial & correction policy.