UCFL311 bearing: complete specifications & equivalents
The UCFL311 is a JIS B 1559 radial bearing sized 55 x 120 x 66 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 | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 66 mm |
| Seal / shield | 2RS |
| Basic dynamic load rating C | 79.5 kN |
| Basic static load rating C0 | 45 kN |
| Fatigue load limit Pu | 3.5 kN |
| Mass | 4600 g |
| Housing height H | 250 mm |
| Housing overall length L | 150 mm |
| Mounting bolt center distance J | 198 mm |
| Mounting hole diameter N | 25 mm |
| Manufacturer designation | UCFL311 |
| 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 | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 2.598 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 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) | 11 of 25 |
| Bore above smallest UCFL-series size | 43 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| UCFL311 | 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 UCFL311 model number is decoded
In NTN's mounted-bearing range, UCFL311 is the two-bolt rhombus flange option for a 55 mm shaft: insert UC311D1, housing FL311, through-bolt mounting. The code breaks down as insert family UC, housing form FL (flange), duty series 3, bore code ending in the 55 mm shaft size; the unit is built from insert UC311D1 and housing FL311. For the frame-face drawing of UCFL311: the two holes are 198 mm apart (J), the rhombus spans 150 mm (L) and 250 mm (H), and M22 (25 mm) bolts clamp it around the 55 mm shaft. 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. In this bore band the X and 3 sections start to outsell the standard section: longer bearing centres and tensioned belt drives use the extra rating and stiffer base that the heavier housings provide. Quarry and aggregate conveyors specify this unit because maintenance crews can unbolt the whole assembly and swap it in minutes; interchangeability across brands at the JIS dimensions is part of the selection logic. Cold-climate users should order the low-temperature grease option or repack before commissioning: the factory fill is a general-purpose NLGI 2 that channels poorly below about −20 °C and starves the ball set on start-up. Basic ratings of the UC311D1 insert are 79.5 kN dynamic and 45 kN static; the assembled UCFL311 weighs about 4.6 kg.
Typical equipment & failure modes
Common applications
- quarry feeder and transfer drives
- sawmill arbors and feed rolls
- cement and clinker handling
- elevated-temperature positions where grease life, not bearing rating, sets the interval
Known failure patterns
- setscrew loosening and inner-ring fretting on a shaft that was never re-torqued after run-in
- insert brinelling from hammer mounting or from belt tension applied to a stationary unit
- over-greasing that churns the charge, overheats the bearing and blows the seal lip
Selection pitfalls — read before you substitute
- Never weld a bracket to the FL311 housing of UCFL311: local heat cracks cast iron and distorts the spherical bore that the insert depends on.
- Heavy drives on UCFL311 should have the setscrews re-torqued after the first day; at 55 mm bore the seating forces are large and a loose inner ring frets the shaft in weeks.
- The 3-series insert makes UCFL311 the highest-rated unit at 55 mm; its advantage disappears on a soft foundation, so spend the saved margin on base stiffness rather than skipping shims.
- As a rhombus flange, UCFL311 pulls against the frame through only two M22 bolts on 198 mm centres; the mounting plate must be stiff enough not to bend between them under belt load.
Frequently asked questions
How is UCFL311 locked to the shaft, and how tight should the setscrews be?
The UC311D1 insert uses two collar setscrews on the 55 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 UCFL311 instead of a pillow block?
Choose the UCFL311 two-bolt flange when the 55 mm shaft meets a vertical frame or side plate: the diamond housing bolts flush with two M22 bolts on 198 mm centres. A UCP pillow block is used when the shaft runs above a horizontal mounting surface.
What are the dimensions of an UCFL311 mounted bearing?
UCFL311 takes a 55 mm shaft (insert UC311D1, 120 mm OD) and has a unit mass of about 4.6 kg. Flange figures: height H 250 mm, length L 150 mm, bolt centres J 198 mm, holes 25 mm for M22 bolts.
What does the UCFL311 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 55 mm bore. UCFL311 is built from housing FL311 plus insert UC311D1 (D1 = greasable).
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.