UC321 Bearing Dimensions
UC321 insert bearing: 105 mm bore, 225 mm spherical OD, 112 mm width, set-screw lock. Fits P321/F321/FL321/T321 housings. Quote.
UC321 specifications
| Bore d | 105 mm |
|---|---|
| Outside diameter D | 225 mm |
| Inner ring width B | 112 mm |
| Outer ring width C | 56 mm |
| Seal / shield options | Sealed insert bearing (UC type), spherical outside diameter, set-screw locking |
| Material | GCr15 chrome bearing steel (rings and rolling elements) |
| 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 UC321 designation
| Segment | Meaning |
|---|---|
| UC | Insert bearing with set-screw locking and spherical outside diameter |
| 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). |
UC321 interchange
UC321 is an ISO designation. The boundary dimensions are identical across manufacturers; only suffixes (seals, clearance, cage) differ.
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.
UC321 compared with nearby sizes and housings
UC321 is a set-screw insert for a 105 mm shaft: outside diameter 225 mm, inner ring width 112 mm and outer ring width 56 mm.
The UC321 insert is the one fitted in UCP321 (pillow block unit) and UCFL321 (oval flange unit).
UC326 is the next larger size in the same series on this site: shaft d 130 mm (25 mm more), outside diameter D 280 mm (55 mm more) and inner ring width B 135 mm (23 mm more).
UC315 is the next smaller size in the same series on this site: shaft d 75 mm (30 mm less), outside diameter D 160 mm (65 mm less) and inner ring width B 82 mm (30 mm less).
| Model | Type | Main dimensions | Weight (kg) |
|---|---|---|---|
| UC321 | insert bearing (this page) | 105 × 225 × 112 mm (d × D × B) | — |
| UC315 | insert bearing | 75 × 160 × 82 mm (d × D × B) | 4.68 |
| UC326 | insert bearing | 130 × 280 × 135 mm (d × D × B) | — |
| UCP321 | pillow block unit | d 105 · H 140 · J 380 mm | — |
| 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.
UC321 load ratings
FULI's catalog has no load rating line for UC321 itself, so none is given here. Ask us and we send the figures with the quotation.
UC321 dimensions in inches
The nearest common inch shaft size to the 105 mm bore of UC321 is 4-1/8 in (104.78 mm), 0.22 mm smaller than the bore, so UC321 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 |
|---|---|---|
| Bore d | 105 mm | 4.1339 in |
| Outside diameter D | 225 mm | 8.8583 in |
| Inner ring width B | 112 mm | 4.4094 in |
| Outer ring width C | 56 mm | 2.2047 in |
Converted at 1 in = 25.4 mm and rounded to four decimals. The bearing itself is made to the millimetre sizes.
Mounting UC321 (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.
UC321 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.
The spherical outside diameter of UC321 lets the insert swivel in the housing seat while it is being mounted, which takes up small errors in shaft line. It does not make the bearing a self-aligning bearing in service.
Grease for UC321
The insert is sealed on both sides and greased at the factory. Fitted in a housing with a grease fitting, it can be relubricated through the housing; on its own it runs on the factory fill.
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 UC321
FULI supplies UC321 on its own as a replacement insert, or fitted in a housing as a complete unit. The rings and balls are GCr15 chrome steel and the radial clearance is C0 as standard, with C3 on request.
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 UC321.
Tools and guides for UC321
Typical applications
- Replacement inserts for UCP / UCF / UCFL housings
- Conveyors
- Agricultural machinery
FAQ
What shaft size does UC321 fit?
A 105 mm shaft (4.1339 in).
What is the difference between UC321 and UC326?
UC326 is the next size up, for a 130 mm shaft, with outside diameter D 280 mm (55 mm more) and inner ring width B 135 mm (23 mm more). Choose UC326 when the shaft is larger or the load is higher; the housings are not interchangeable.
Which housings fit the UC321 insert?
UCP321 (pillow block unit) and UCFL321 (oval flange unit) all use UC321. Order UC321 on its own to replace a worn insert in any of them.
Can UC321 be ordered as an insert only, or as a complete unit?
Both. UC321 can be supplied on its own as a replacement insert for an existing housing, or fitted in a housing such as the UCP321 pillow block or UCF321 square flange and supplied as a complete unit. Tell us which you need when you send the inquiry.
Where are the load ratings for UC321?
Load ratings for UC321 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.