UCFL321 bearing: complete specifications & equivalents
The UCFL321 is a JIS B 1559 radial bearing sized 105 x 225 x 112 mm (bore x OD x width) with 2RS sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 105 mm |
| Outer diameter D | 225 mm |
| Width B | 112 mm |
| Seal / shield | 2RS |
| Basic dynamic load rating C | 204 kN |
| Basic static load rating C0 | 153 kN |
| Fatigue load limit Pu | 9.35 kN |
| Mass | 27000 g |
| Housing height H | 440 mm |
| Housing overall length L | 270 mm |
| Mounting bolt center distance J | 360 mm |
| Mounting hole diameter N | 44 mm |
| Manufacturer designation | UCFL321 |
| Standard | JIS B 1559 |
| Catalog version | CAT. No. 2203-3/E 2024 |
| Last verified | 2026-09-25 |
Source: catalog reference (CAT. No. 2203-3/E 2024) · extracted 2026-09-25
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (CAT. No. 2203-3/E 2024); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & UCFL-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 8.858 in |
| Width B | 4.409 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 60 mm |
| Smallest bore in UCFL-series | 12 mm |
| Largest outer diameter in UCFL-series | 300 mm |
| Width range across UCFL-series | 31–145 mm |
| Bore position in UCFL-series (smallest first) | 21 of 25 |
| Bore above smallest UCFL-series size | 93 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| UCFL321 | ISO 15 | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | ISO 15 boundary-dimension envelope; seal suffix convention varies by brand (2RS / DDU / LLU / 2RSR) — verify seal design and temperature range. Brand-specific OEM equivalents 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 UCFL321 model number is decoded
NTN delivers UCFL321 as a matched unit — the UC321D1 insert is locked into the FL321 rhombus cast-iron flange at the factory and arrives greased and sealed. NTN's numbering ties the unit to its components: UCFL321 means the FL321 housing carrying the UC321D1 insert, with the last two digits denoting the 105 mm bore in the 3-series duty class. The mounting detail needs four numbers: H 440 mm flange height, L 270 mm across the ears, J 360 mm between the 44 mm holes, and a 105 mm shaft through the 225 mm OD UC321D1 insert. The 3-series section is the heavy-duty end of the range: a UC3 high-capacity insert in the longest, strongest housing, specified for shock loads and long conveyor centres. The diamond flange carries the shaft square to a vertical face — a welded frame, side plate or gearbox wall — so no base plinth and no shim pack under the bearing are required. Above 90 mm bore these are primary process drives — mining conveyors, bulk materials handling, heavy fans — where the 3-series insert and massive casting protect against shock and contamination. Crane and hoist travel drives occasionally use this unit when the shaft runs parallel to the rail: the pillow base bolts to a machined trolley plate and survives repeated travel shocks. When a shaft journal is scored under the setscrew points, do not rotate the insert to a fresh spot on the same shaft — sleeve the journal or move the unit, or the indentations let the ring creep again. Basic ratings of the UC321D1 insert are 204 kN dynamic and 153 kN static; the assembled UCFL321 weighs about 27.0 kg.
Typical equipment & failure modes
Common applications
- large induced-draft fans
- quarry and aggregate screens
- ship-loader and stacker drives
- low-speed heavily loaded pulleys where the static rating governs the selection
Known failure patterns
- lip-seal failure from grit past the slinger, followed by grease loss and abrasive wear
- spherical-seat fretting that welds insert to housing and destroys the self-aligning action
- water-emulsified grease after washdown with the fitting facing upward
Selection pitfalls — read before you substitute
- As a rhombus flange, UCFL321 pulls against the frame through only two M39 bolts on 360 mm centres; the mounting plate must be stiff enough not to bend between them under belt load.
- The D1 suffix on UC321D1 means the greasable execution; a unit without it has no fitting path, so do not assume every UCFL321 on site accepts relubrication.
- Self-aligning is not the same as free to move: the UC321D1 insert of UCFL321 pivots to correct static misalignment, but a continuously bending shaft still frets the spherical seat.
- At 105 mm bore, rigging and alignment dominate the UCFL321 installation: the cast unit is lifted into place on the shaft, aligned on the spherical seat, and only then foot-bolted.
- The 3-series insert makes UCFL321 the highest-rated unit at 105 mm; its advantage disappears on a soft foundation, so spend the saved margin on base stiffness rather than skipping shims.
Frequently asked questions
What does the UCFL321 designation mean?
UC identifies the wide-inner-ring, setscrew-locking ball bearing insert; FL the two-bolt rhombus flange housing; 3 is the duty series; the last digits encode the 105 mm bore. UCFL321 is built from housing FL321 plus insert UC321D1 (D1 = greasable).
How is UCFL321 locked to the shaft, and how tight should the setscrews be?
The UC321D1 insert uses two collar setscrews on the 105 mm shaft. Tighten them to NTN's torque table for this bore size in sequence — half torque on the first, full on the second, then back to the first — and re-torque after the first 24–48 running hours once the collar has seated.
When should I choose a rhombus flange unit like UCFL321 instead of a pillow block?
Choose the UCFL321 two-bolt flange when the 105 mm shaft meets a vertical frame or side plate: the diamond housing bolts flush with two M39 bolts on 360 mm centres. A UCP pillow block is used when the shaft runs above a horizontal mounting surface.
Is the UCFL321 bearing self-aligning?
Yes within limits. The UC321D1 insert has a spherical outer diameter that pivots in the FL321 housing bore, compensating for a few degrees of static misalignment between shaft and foundation. It does not compensate for a bent shaft or dynamic deflection while running.
What are the dimensions of an UCFL321 mounted bearing?
UCFL321 takes a 105 mm shaft (insert UC321D1, 225 mm OD) and has a unit mass of about 27.0 kg. Flange figures: height H 440 mm, length L 270 mm, bolt centres J 360 mm, holes 44 mm for M39 bolts.
Reviewed & verified by the MPN Base engineering desk against source catalog CAT. No. 2203-3/E 2024 on 2026-09-25. Read our editorial & correction policy.