SKF NU 321 ECML/C3B20 cylindrical roller bearing
- Brand
- SKF
- Category
- Bearings
- Subcategory
- Cylindrical roller bearings
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Decoding SKF NU 321 ECML/C3B20
- NU 3Series
- Cylindrical roller bearings, NU 3 series. Series differ in outside diameter and width even when the bore is the same.
- 21Bore
- Bore 105 mm (21 × 5).
- ECML/C3B20Suffix
- SKF suffix: identifies the variant, such as seals or shields, cage, internal clearance or other features.
NU 321 is the standard ISO basic designation, which sets the bearing type, series and bore.
Description
SKF NU 321 ECML/C3B20 measures 105 mm across the bore and 225 mm across the outside diameter; its width is 49 mm (105 x 225 x 49 mm).
SKF NU 321 ECML/C3B20 belongs to cylindrical roller bearing, part of our Bearings range. Tell us how many you need by WhatsApp or email and we'll get back to you promptly with a quote for NU 321 ECML/C3B20 and any equivalents.
For operations that demand reliable support under heavy radial loads, SKF NU series cylindrical roller bearings deliver the rigidity and precision required in critical machinery. Their robust design and machined brass cage make them a practical choice for gearboxes, pumps, and power transmission equipment. MR Industrial Accessories LLC supplies this line to maintenance and purchasing teams across the United States, Canada, Mexico, and South America.
The NU designation means the outer ring has two integral ribs while the inner ring has none, allowing axial displacement in either direction. The numeric portion (e.g., 218, 219, 221, 222, 321, 322) identifies the size and dimension series. Suffixes provide additional details: EC indicates high-capacity rollers, ML a machined brass cage guided by the rollers, C3 increased internal radial clearance, and B20 a specific design modification. Reading these codes correctly helps you specify the exact bearing for your application.
Common installations include steel, cement, mining, paper, and general machinery manufacturing. These bearings are also found in speed reducers, centrifugal pumps, industrial fans, and transmission equipment where high radial load capacity and rigidity are essential. Their performance under demanding conditions makes them suitable for shafts that require precise alignment and long service intervals.
When selecting a bearing, consider the radial load, rotational speed, and operating environment. The C3 clearance is often specified when thermal gradients between inner and outer rings are expected. The ML machined brass cage is well suited to higher speeds. During mounting, pay close attention to shaft and housing alignment, and use the proper lubrication—grease or oil—based on the application. Cleanliness and correct fits help prevent premature failure.
If you need a replacement, verify the bore, outside diameter, and width, along with any suffixes that affect performance. Interchangeability with other brands is not always direct, so checking internal clearance and cage design is important. Send the full part number to MR Industrial Accessories LLC via WhatsApp or email, and our team will help you identify the right bearing or suggest an equivalent.
Dimensions
105 x 225 x 49 mm (d x D x B): boundary dimensions for basic designation NU 321, according to ISO 15.
- Bore
- 105mm
- Outside diameter (D)
- 225mm
- Width (B)
- 49mm
Same size, other brands
Other brands' pages with basic designation NU 321: 105 x 225 x 49 mm (d x D x B) per ISO 15.
What they share are the ISO 15 boundary dimensions, not the specs: seals or shields, internal clearance, cage and load rating may vary with brand and suffix. Every quote is by full part number.
Frequently asked questions
- SKF NU 321 ECML/C3B20 bearing: what are its dimensions?
- SKF NU 321 ECML/C3B20 measures 105 mm across the bore and 225 mm across the outside diameter; its width is 49 mm (105 x 225 x 49 mm). Those are the boundary dimensions standardized in ISO 15 for basic designation NU 321.
- What does the C3 suffix mean in an SKF NU bearing?
- C3 indicates a greater internal radial clearance than standard. It is used when operating conditions create temperature differences between the inner and outer rings, or when extra clearance is needed to compensate for thermal expansion.
- How does the NU series differ from other cylindrical roller bearing series?
- The NU series has two ribs on the outer ring and none on the inner ring, permitting axial displacement in both directions. Other series, such as NJ or NUP, have different rib configurations to limit axial movement in one or both directions.
- Can an SKF NU bearing be replaced by a bearing from another brand?
- Check that the bore, outside diameter, and width match, and that the design and suffixes are equivalent. Not all bearings are directly interchangeable; internal clearance and cage type can affect performance. Contact MR Industrial Accessories LLC for assistance in verifying compatibility.