The SKF 6304-2Z/C3 is a single row deep groove ball bearing with a 20 mm bore, 52 mm outside diameter and 15 mm width, fitted with a non-contact metal shield on both sides (2Z) and C3 radial internal clearance. It belongs to the SKF Explorer performance class and, per SKF, carries a basic dynamic load rating of 16.8 kN and a basic static load rating of 7.8 kN.
The designation can be read directly: 6 = single row deep groove ball bearing, 3 = ISO dimension series 03 (medium), a heavier cross-section with larger balls for higher loads on the same shaft size; 04 = bore code for 20 mm (04 x 5); 2Z = shields on both sides; C3 = radial internal clearance greater than normal.
Shields leave a narrow gap to the inner ring, so friction stays low and SKF lists a limiting speed of 15,000 r/min for this version, compared with 9,500 r/min for the sealed 6304-2RSH/C3. That makes the 2Z design the usual choice for electric motors, fans and other clean, fast-running positions.
Technical data
| SKF designation | 6304-2Z/C3 |
|---|---|
| Bearing type | Single row deep groove ball bearing |
| Dimension series | 63 – ISO dimension series 03 (medium) |
| Bore diameter (d) | 20 mm |
| Outside diameter (D) | 52 mm |
| Width (B) | 15 mm |
| Basic dynamic load rating (C) | 16.8 kN |
| Basic static load rating (C0) | 7.8 kN |
| Reference speed | 30,000 r/min |
| Limiting speed | 15,000 r/min |
| SKF performance class | SKF Explorer |
| Sealing | Shield on both sides (non-contact) |
| Radial internal clearance | C3 (greater than normal) |
| Cage | Sheet metal (pressed steel) |
| Bore type | Cylindrical |
| Lubricant | Grease, no relubrication feature |
| Material | Bearing steel |
| Net weight | 0.146 kg |
| Condition | New, original SKF |
Typical applications
- Heavier electric motors and generators
- Machine-tool and woodworking spindles running at moderate speed
- Fans, blowers and ventilation units
- Compressors and vacuum pumps
- Like-for-like replacement of a worn SKF 6304-2Z/C3
Compatibility and replacement
Every 6304 bearing made to ISO 15 has the same 20 x 52 x 15 mm boundary dimensions, so this bearing fits wherever a 6304 with shields and C3 clearance from another maker was used. Suffixes differ between brands: shields are often marked ZZ or 2Z, contact seals 2RS, 2RS1, DDU or LLU, and the clearance C3 may appear as “C3” or “/C3”. Always match the sealing arrangement and the clearance class shown on the old bearing; if your machine needs the other closure, the 6304-2RSH/C3 is the same size.
Frequently asked questions
What is the difference between 6304-2Z/C3 and 6304-2RSH/C3?
Only the closures. The 6304-2Z has non-contact steel shields; the 2RSH version has contact rubber seals. Per SKF, the limiting speed is 15,000 r/min for 2Z and 9,500 r/min for 2RSH; the load ratings are the same. Choose shields for speed and low friction, seals for dirt and moisture.
What do the load ratings mean in practice?
The basic dynamic load rating C (16.8 kN) is used to calculate rating life: under ISO 281, a ball bearing loaded at one tenth of C has a basic rating life of 1,000 million revolutions. The static rating C0 (7.8 kN) is the reference for heavy loads at very low speed or standstill.
Which shaft and housing does it fit?
A 20 mm shaft seat and a 52 mm housing bore, with 15 mm of axial space. The exact fit tolerances depend on the load and on which ring rotates, so follow the machine drawing or the old bearing seat.
Related parts
- SKF 6304-2RSH/C3 (sealed version)
- SKF 6303-2Z/C3 (17 mm bore)
- SKF 6305-2Z/C3 (25 mm bore)
- All SKF 6300 Series Bearings
Part of the SKF 6300 series stocked by RendatSP for electric motors, gearboxes, pumps, fans, conveyors and general industrial machinery, with fast shipping to Iraq, Saudi Arabia, UAE, Egypt, Yemen, Libya and across the Middle East and Africa.
Every part RendatSP supplies is new and original, carries a 1-year warranty and ships worldwide by air in 5 to 7 days once ready (shipping, payment and warranty). Send us the part number and quantity on WhatsApp or through the inquiry form and we will quote the same working day. Agents in Saudi Arabia, Iraq, the UAE, Egypt, Oman, Libya, Morocco, Mauritania, Yemen, Algeria and Jordan.
