UCP308 bearing: complete specifications & equivalents
The UCP308 is a JIS B 1559 radial bearing sized 40 x 90 x 52 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 | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 52 mm |
| Seal / shield | 2RS |
| Basic dynamic load rating C | 45 kN |
| Basic static load rating C0 | 24 kN |
| Fatigue load limit Pu | 1.83 kN |
| Mass | 3000 g |
| Housing height H | 60 mm |
| Housing overall length L | 220 mm |
| Mounting bolt center distance J | 170 mm |
| Mounting hole diameter N | 17 mm |
| Manufacturer designation | UCP308 |
| 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 & UCP-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 2.047 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in UCP-series | 12 mm |
| Largest outer diameter in UCP-series | 300 mm |
| Width range across UCP-series | 31–145 mm |
| Bore position in UCP-series (smallest first) | 8 of 25 |
| Bore above smallest UCP-series size | 28 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| UCP308 | 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 UCP308 model number is decoded
NTN ships the UCP308 as a matched assembly — UC308D1 insert swaged into the P308 cast-iron pillow block — so the fitter never has to set bearing-to-housing clearance. The code breaks down as insert family UC, housing form P (pillow block), duty series 3, bore code ending in the 40 mm shaft size; the unit is built from insert UC308D1 and housing P308. For layout work on UCP308: the 40 mm shaft centre sits 60 mm above the sole (H), the footprint is 220 mm long (L), bolt centres are 170 mm (J), and the foot holes suit M14 (17 mm) bolts. 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 upright base carries the shaft parallel to and above the mounting surface, which is the arrangement fan, conveyor and transmission drives use whenever a plinth or rail is available. The 25–50 mm bore band is the workhorse of industry — belt conveyors, fans, agricultural drives and small process machines — which is why this range has the fullest choice of series and cover options. Sugar and fertiliser handling relies on this unit where corrosion and fine crystals attack everything: the sealed insert and the grease nipple let crews purge contaminated grease after each campaign. Check the shaft itself is straight to roughly 0.05 mm over the bearing centres before blaming a noisy new unit: mounted bearings accept housing misalignment but cannot offset a bent shaft. Basic ratings of the UC308D1 insert are 45 kN dynamic and 24 kN static; the assembled UCP308 weighs about 3.0 kg.
Typical equipment & failure modes
Common applications
- small crushers and screening feeds
- textile line-shafting
- machine-tool chip conveyors
- fan drives where belt tension, not transmitted torque, sets the radial load
Known failure patterns
- grease starvation on long intervals in hot positions, with the ball set running on dried thickener
- fretting corrosion of the shaft journal under the wide inner ring after years of micro-creep
- lip-seal failure from grit past the slinger, followed by grease loss and abrasive wear
Selection pitfalls — read before you substitute
- The 3-series insert makes UCP308 the highest-rated unit at 40 mm; its advantage disappears on a soft foundation, so spend the saved margin on base stiffness rather than skipping shims.
- As a pillow block, UCP308 needs a prepared horizontal surface at the 60 mm centre height: shim both feet with full-width packs so the 220 mm base seats over its full area.
- The lip seals and slingers on UCP308 suit ordinary industrial dust; submerged or heavy slurry service needs a different sealed arrangement regardless of the load rating.
- Never weld a bracket to the P308 housing of UCP308: local heat cracks cast iron and distorts the spherical bore that the insert depends on.
- In this bore band the temptation is to choose UCP308 on shaft size alone; belt pull often dominates the radial load, so rate the unit against the overhung pulley force, not just transmitted power.
Frequently asked questions
What are the dimensions of an UCP308 mounted bearing?
UCP308 takes a 40 mm shaft (insert UC308D1, 90 mm OD) and has a unit mass of about 3.0 kg. Housing figures: centre height H 60 mm, length L 220 mm, bolt centres J 170 mm, foot holes 17 mm for M14 bolts.
What does the UCP308 designation mean?
UC identifies the wide-inner-ring, setscrew-locking ball bearing insert; P the upright pillow block housing; 3 is the duty series; the last digits encode the 40 mm bore. UCP308 is built from housing P308 plus insert UC308D1 (D1 = greasable).
How is UCP308 locked to the shaft, and how tight should the setscrews be?
The UC308D1 insert uses two collar setscrews on the 40 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 pillow block like UCP308 instead of a flanged unit?
Choose the UCP308 pillow block when the shaft runs parallel to a horizontal base plate, rail or plinth — the upright housing holds the shaft centre 60 mm above the 220 mm bolt-down base. Choose a UCFL flange when the shaft meets a vertical frame face and the housing bolts flat against it.
How often should I relubricate an UCP308 unit?
There is no single interval for UCP308: the UC308D1 insert is regreased through the D1 fitting while the shaft turns, using an NLGI 2 lithium or lithium-complex grease. Quarterly is typical for normal ambient conveyor duty; shorten to weekly or monthly where temperatures exceed about 70 °C, water is present, or dust is heavy.
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.