UCP321 Bearing Dimensions
UCP321 pillow block bearing unit: 105 mm bore, 380 mm bolt centres, 140 mm centre height. P321 housing + UC321 insert, designation, size-equivalent codes.
UCP321 specifications
| Shaft diameter d | 105 mm |
|---|---|
| Centre height H | 140 mm |
| Base length L | 490 mm |
| Bolt hole spacing J | 380 mm |
| Overall height H0 | 280 mm |
| Insert width B | 112 mm |
| Mounting bolt | M30 |
| Seal / shield options | Sealed insert bearing (UC type) with cast iron housing |
| Material | Insert: GCr15 chrome bearing steel (rings and rolling elements); housing: cast iron |
| Precision | P0 (standard) |
| Radial clearance | C0 (standard); C3 on request |
| Load ratings | Load ratings for this model are being checked against FULI's catalog. Ask for them with the quote. |
Dimensions cross-checked against published catalogues; please confirm with your quote.
How to read the UCP321 designation
| Segment | Meaning |
|---|---|
| UC | Insert bearing with set-screw locking and spherical outside diameter |
| P | Pillow block (plummer block) housing |
| 3 | 300 series (medium duty) |
| 21 | Bore code 21 → 105 mm bore. ISO bore code (00–03 = 10/12/15/17 mm; 04 and above = code × 5 mm). |
UCP321 interchange
UCP321 is a housed unit: a UC321 insert bearing in a P321 housing. The insert bearing dimensions follow ISO and interchange between manufacturers. Housing dimensions such as bolt hole spacing can differ between the JIS and ISO versions of the same designation, so please confirm the mounting dimensions with us before ordering.
Brand numbers for UCP, UCF and UCFL units: Pillow Block Bearing Cross Reference.
Brand names are trademarks of their respective owners. FULI is not affiliated with, authorized by or endorsed by these companies. Part numbers are shown for interchange reference only. FULI dimensions, load ratings and speeds come from the FULI catalog.
UCP321 compared with nearby sizes and housings
UCP321 is a pillow block unit that holds the UC321 insert on a 105 mm shaft: centre height H 140 mm, base length L 490 mm and overall height H0 280 mm with M30 bolts.
The same 321 size is also made as UCFL321 (oval flange unit, d 105 · L 440 · J 360 mm). All of them take the same UC321 insert, so a worn insert can be changed without changing the housing type.
UCP326 is the next larger size in the same series on this site: shaft d 130 mm (25 mm more), inner ring width B 135 mm (23 mm more), centre height H 180 mm (40 mm more), length L 600 mm (110 mm more), bolt spacing J 480 mm (100 mm more) and overall height H0 355 mm (75 mm more), and it takes M33 bolts instead of M30.
| Model | Type | Main dimensions | Weight (kg) |
|---|---|---|---|
| UCP321 | pillow block unit (this page) | d 105 · H 140 · J 380 mm | — |
| UCP326 | pillow block unit | d 130 · H 180 · J 480 mm | — |
| UC321 | insert bearing | 105 × 225 × 112 mm (d × D × B) | — |
| UCFL321 | oval flange unit | d 105 · L 440 · J 360 mm | — |
Dimensions in mm from the model pages; weight from FULI's catalog, — = not listed on this site.
UCP321 load ratings
FULI's catalog has no load rating line for UCP321 itself, so none is given here. The ratings of the UC321 insert are on its own page. Ask us and we send the figures with the quotation.
UCP321 dimensions in inches
The nearest common inch shaft size to the 105 mm bore of UCP321 is 4-1/8 in (104.78 mm), 0.22 mm smaller than the bore, so UCP321 would be loose on it. An inch shaft needs an inch bore insert. Inch bore versions are made for some sizes; ask us with the shaft size.
| Dimension | Millimetres | Inches |
|---|---|---|
| Shaft diameter d | 105 mm | 4.1339 in |
| Centre height H | 140 mm | 5.5118 in |
| Base length L | 490 mm | 19.2913 in |
| Bolt hole spacing J | 380 mm | 14.9606 in |
| Overall height H0 | 280 mm | 11.0236 in |
| Insert width B | 112 mm | 4.4094 in |
Converted at 1 in = 25.4 mm and rounded to four decimals. The bearing itself is made to the millimetre sizes.
Mounting UCP321 (general guidance)
General guidance, not a FULI specification: insert bearings slide onto the shaft rather than being pressed on, and are held by their locking device. A shaft ground or drawn to h7 is common; a closer shaft such as js7 or j7 suits higher speed.
The UC321 insert in UCP321 is locked by set screws in the extended inner ring. Housed-unit problems usually start at the set screws: if the inner ring is not held, it turns on the shaft and wears it. Tighten each screw to the torque in the mounting instructions, and check them again after the first hours of running.
Bolt UCP321 down with M30 bolts at 380 mm spacing on a flat, rigid face. Line up the two housings on a shaft before tightening the bolts fully, then lock the inserts, so the shaft is not bent between them.
Grease for UCP321
The insert in UCP321 is sealed on both sides and greased at the factory. If the housing has a grease fitting, add grease slowly through it while the shaft turns until a little fresh grease shows at the seals; general practice is to relubricate more often in wet or dusty places.
Greases for a stated temperature range can be specified on the order; for North America a range of −40 to 120 °C is often asked for.
How FULI supplies UCP321
FULI supplies UCP321 as a complete unit, or the UC321 insert on its own for replacement. Before packing, the factory checks the mounting torque, the fit of the insert in the housing, the radial clearance and that the base-to-centre height is consistent across the batch.
Rings are marked with a brand you are authorised to use, with the FULI brand, or left neutral, as your order states. The box is printed with the model, precision class and brand.
Inquiries that leave out the prefix or suffix letters are the usual cause of a wrong quote, so write the full designation, for example UCP321.
Tools and guides for UCP321
Typical applications
- Conveyors
- Fans and blowers
- Agricultural machinery
- Grain and food processing lines
FAQ
What shaft size does UCP321 fit?
A 105 mm shaft (4.1339 in).
What is the difference between UCP321 and UCP326?
UCP326 is the next size up, for a 130 mm shaft, with inner ring width B 135 mm (23 mm more), centre height H 180 mm (40 mm more), length L 600 mm (110 mm more), bolt spacing J 480 mm (100 mm more) and overall height H0 355 mm (75 mm more). It takes M33 bolts. Choose UCP326 when the shaft is larger or the load is higher; the housings are not interchangeable.
Which insert fits UCP321?
The UC321 insert (105 × 225 × 112 mm). It is sold on its own for replacement.
UCP321 or UCFL321: which should I use?
Both hold the same UC321 insert on a 105 mm shaft. UCP321 is a pillow block unit (d 105 · H 140 · J 380 mm); UCFL321 is a oval flange unit (d 105 · L 440 · J 360 mm). Choose by how the bearing is fixed to the machine: a pillow block bolts to a surface parallel to the shaft, a flange to a face across it.
Does UCP321 come as a complete unit or insert only?
UCP321 is normally supplied as a complete unit (insert bearing already fitted in the housing). The insert can also be quoted separately if you are replacing only the bearing.
Where are the load ratings for UCP321?
Load ratings for UCP321 are being checked against FULI's catalog and are not shown on this page yet. Model pages with a "Load ratings & speed" table carry values from FULI's catalog.