Description
Authorized Channel Sourcing — Every SKF NNU4984BK/SPW33 leaves the factory with batch-level traceability tied to official distribution documentation, so procurement teams can confirm origin before the crate reaches the port.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | SKF NNU4984BK/SPW33 |
| Bearing Type | Double Row Cylindrical Roller Bearing |
| Bore Diameter (d) | 420 mm |
| Outside Diameter (D) | 560 mm |
| Width (B) | 140 mm |
| Number of Rows | Double Row |
| Precision Class | SP |
| Seal or Shield Type | Open |
| Bore Type | Tapered (K) |
| Outer Ring Feature | W33 — annular groove with three lubrication holes |
| Dynamic Load Rating (C) | 1 510 kN |
| Weight | approx. 91 kg |
| Origin | China |
Note: The suffix BK appears on the product label but its exact meaning is not confirmed in publicly available SKF catalog excerpts; verify the full suffix string with the manufacturer’s documentation before final specification lock-in.
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel & Metallurgy | Rolling mill work roll necks, continuous caster guide rolls |
| Mining & Crushing | Crusher eccentric shafts, vibrating screen drive shafts |
| Heavy Industrial Gearboxes | Large planetary gear carrier supports |
| Material Handling | Stackers and reclaimers slew pivot bearings |
What a Precision Miss Costs on a Rolling Mill Neck
SP precision is not a luxury on 420 mm bore cylindrical roller bearings — it is the margin between controlled runout and a scrapped roll.
When maintenance teams replace rolling mill bearings by matching only the base designation, they often overlook the SP class requirement. The result is excessive radial runout under heavy radial load, which transfers directly into strip thickness variation on the mill stand. A significant share of premature bearing failures in continuous-operation steel plants traces back to this kind of cross-reference error where precision class, clearance, and lubrication suffixes were never verified against the OEM print [NEED_CITE: rolling bearing failure mode classification per ISO 15243]. The SKF NNU4984BK/SPW33 double row cylindrical roller bearing addresses this gap by combining SP running accuracy with the W33 relubrication feature that high-duty-cycle mill environments demand.
Matching the Bearing to Continuous Mill and Crusher Loads
Rolling mill necks and crusher eccentric shafts share one unforgiving trait: sustained heavy radial load with minimal axial displacement. The double row cylindrical arrangement in the NNU4984BK/SPW33 handles that load profile by distributing stress across two full-complement roller rows, while the tapered bore allows fine radial clearance adjustment during mounting — essential when interference fits on large shafts can collapse internal clearance. Our cross-reference database aligns the precision class, bore geometry, and W33 lubrication path against OEM equipment numbers so that substitutions from other authorized brands carry the same functional suffix stack rather than a bare base number match.
Thermal Growth, Lubrication Intervals, and the W33 Advantage
In a vibrating screen running at ambient desert temperatures above 45 °C, internal clearance shrinks as the shaft and housing expand at different rates. Open-type bearings like the NNU4984BK/SPW33 allow maintenance crews to flush and relubricate on a schedule matched to the operating temperature, rather than being locked into a sealed-for-life design that cannot survive continuous contamination ingress. The W33 annular groove and three circumferential lubrication holes feed grease directly into the roller path, shortening relubrication intervals and reducing the chance of dry running between service stops [NEED_CITE: effect of relubrication interval on cylindrical roller bearing service life].
Decoding the Critical Suffixes
The SP precision class tightens running accuracy well beyond standard P0 and P6 grades, limiting radial runout to levels acceptable for roll-neck and spindle applications where dimensional consistency of the finished product matters. The K tapered bore enables the bearing to be driven up a 1:12 taper shaft seat during mounting, which sets residual internal clearance precisely — a procedure far more repeatable than shimming on a straight bore. The W33 outer ring groove and lubrication holes eliminate the need to drill custom passages in the housing, ensuring lubricant reaches the loaded zone regardless of bearing orientation. Together, these suffixes define a bearing engineered for applications where thermal growth, heavy radial load, and continuous contamination are the baseline, not the exception.
The Downtime Equation Nobody Models
Correct specification paired with traceable supply avoids a cascade of hidden costs. A bearing installed without the required SP running accuracy may survive initial commissioning but generate vibration signatures that trip online monitoring alarms within months, forcing an unplanned shutdown on a mill line that costs far more per hour than the bearing itself. Counterfeit or re-labeled large-bore cylindrical roller bearings carry soft inner rings that spall under load, sometimes destroying the shaft seat and requiring weeks of machining recovery [NEED_CITE: financial impact of unplanned downtime in continuous process industries]. ISO 281 life calculations assume correct clearance, alignment, and lubrication — inputs that collapse when the installed bearing is not what the specification called for.
How Verification Works Before the Crate Ships
Every NNU4984BK/SPW33 we supply moves through authorized distributor channels with batch-level lot traceability documented at each handoff. We match cross-reference requests against a database that checks precision class, bore type, cage material, and lubrication suffixes as a single package — not a base number lookup that ignores the suffix tail. For import-sensitive destinations, country-of-origin paperwork and HS code documentation ship with the bearing so customs clearance does not stall at the port. Dimensional inspection reports covering bore taper angle, OD roundness, and width variation are available per order, and QR-based authenticity verification through the official SKF app is supported for every unit we deliver.
Documentation & Authenticity
- Supplier Certificate of Conformity referencing the NNU4984BK/SPW33 batch and lot number with authorized channel traceability
- Third-party dimensional inspection report covering 420 mm tapered bore angle, 560 mm OD, and SP-class runout verification before shipment
- Country-of-origin certificate and HS code documentation formatted for Middle East, African, and Latin American customs regimes
- QR code verification pathway compatible with the official SKF app for on-site authenticity confirmation upon receipt
- Material certificate documenting bearing steel grade and heat treatment condition for quality system compliance
Storage, Handling & Mounting
- Keep the SKF NNU4984BK/SPW33 in its original moisture-barrier packaging until the shaft and housing are fully prepped; 91 kg bearings stored in humid yards develop raceway corrosion within weeks
- Mount the tapered bore bearing on a 1:12 taper seat using the hydraulic nut method, measuring axial drive-up distance to achieve the specified residual clearance rather than relying on feel
- Use induction heating for the inner ring only — never flame heat — and monitor temperature with a contact pyrometer to stay below the tempering threshold of the bearing steel
- After mounting, purge fresh grease through the W33 outer ring lubrication holes until clean grease exits both sides, confirming the roller path is fully charged before first rotation
- Store spare units horizontally on a flat pallet; vertical stacking of large-bore cylindrical roller bearings risks brinelling the lower row under static contact stress
Request a Specification-Matched Quotation
Share your mill stand or crusher OEM equipment number and we will return a cross-reference check confirming that precision class, bore type, and W33 lubrication features align with your existing specification. If the application involves non-standard operating temperatures or contaminated environments, include those parameters so we can verify clearance selection before issuing the formal quotation with lead time and pre-shipment inspection scope.
Frequently Asked Questions
Q: How can I confirm the SKF NNU4984BK/SPW33 is genuine before installation?
A: Scan the QR code on the bearing label using the official SKF app to retrieve batch and production data, then cross-check the batch number against the Certificate of Conformity we provide. We also supply authorized channel traceability documentation showing every step from the manufacturer’s distribution network to your site.
Q: What does the W33 suffix mean for relubrication on this bearing?
A: W33 indicates an annular groove on the outer ring with three lubrication holes that channel grease or oil directly into the roller path. On continuous-duty equipment like vibrating screens and rolling mills, this feature allows effective relubrication without dismounting the bearing or drilling custom housing passages.
Q: Why does SP precision class matter compared to standard P0 or P6?
A: SP class provides tighter running accuracy than P0 and P6, which is critical on roll-neck and spindle applications where radial runout directly affects product thickness or surface finish. Installing a standard-precision bearing in an SP-specified position often results in premature vibration alarms and unplanned stops.
Q: What documentation ships with a bulk order of these large-bore bearings?
A: Each shipment includes a Certificate of Conformity with batch traceability, a dimensional inspection report covering bore taper, OD, and width, country-of-origin documentation for customs clearance, and HS code support for import filing. Material certificates are available on request.
Q: Can I substitute a cross-brand equivalent for the NNU4984BK/SPW33?
A: Cross-brand substitution is possible but must match the full suffix stack — SP precision, K tapered bore, and W33 lubrication — not just the base designation. Share your OEM equipment number and we will run a complete cross-reference comparison across authorized brands to confirm interchangeability.
Confirm Your NNU4984BK/SPW33 Specification Package
Send us your OEM equipment number or application parameters — load, speed, temperature, and mounting arrangement — and we will return a verified cross-reference with full documentation scope and lead time.
