How to choose a model — load, speed, size, seal in four steps

Choosing a bearing is not "name a model and done". This page gives a four-step method that uses only the fields our parameter table actually carries, walks it through with a 6205, and is explicit about what it cannot decide — see the last section.

Four steps to narrow it down

Step one: load, via Cr and Cor

Work out the radial load you need, then read two columns:

• for mainly rotating duty, look at Cr (basic dynamic load rating);
• with shock loads or long idle standing loads, look at Cor (basic static load rating).

Catalogue range: Cr 775 N – 81,900 N, Cor 320 N – 52,150 N (see load ratings).

Step two: speed, pick the column that matches lubrication and seal

Three value groups — do not mix them up:

• grease + open / Z / ZZ / RZ / 2RZ → the first column;
• grease + RS / 2RS → the second column (three to four tenths lower);
• oil → the third column.

How the split works, and which models have a blank second column, is in speed and lubrication.

Step three: size, fix the bore then pick the series

The bore is set by the shaft. At the same bore, a larger series number means a larger outer diameter and more capacity:

If the space allows, take the larger series; if not, go smaller and recheck the load in step one.

Step four: seal and lubrication

Dust or moisture → consider rubber seals (RS / 2RS), at the cost of speed ceiling. Clean environment, heat to shed → open or metal shields (Z / ZZ), which run faster.

What each suffix means is covered in bearing suffix codes.

Worked example: 25 mm shaft, 5 kN radial, 3,000 rpm

Input

Four given conditions: a 25 mm shaft, a purely radial load of 5 kN, a speed of 3,000 rpm, and a dusty environment.

Result

1. Size: bore 25 → 6005 / 6205 / 6305 all exist.
2. Load: Cr is 10.1 / 14.0 / 22.45 kN respectively — all above 5 kN, so no model is eliminated here.
3. Speed: the grease 2RS limits are 9,500 / 9,000 / 8,000 rpm, all far above 3,000 rpm — not a constraint either.
4. Seal: dusty → choose 2RS.
5. Conclusion: neither load nor speed binds, so the decision falls back to installation space — tight space use 6005-2RS, normal margin use 6205-2RS, more capacity headroom use 6305-2RS.

⚠️ This conclusion is a table-reading exercise, not a suitability guarantee from us. The reason is in the next section.

What this method cannot decide

No application factor, so Cr is not "enough"

Cr is a rating. Engineering practice applies an application factor, and that factor is not in our parameter table. Therefore:

• we do not say "Cr above your load means it is fine";
• we publish no life in hours (that needs equivalent dynamic load and a duty cycle);
• we give no temperature correction factors and no grease life figures.

Your engineer has to settle these against the real duty. We stand behind the accuracy of the numbers in the table; we do not substitute for your suitability judgement.

No industry admission claims

Different industries have their own admission and certification requirements. We hold no industry admission certificate, so we do not:

• write "suitable for standard X";
• write "certified to Y";
• treat our industry pages as compliance statements. Those pages describe which catalogue models fit which typical duty, nothing more.

Existing entry points

Eight industry pages

See typical duty per industry and the series that fits: industry solutions.

Guided selector

Narrow by condition step by step: bearing selector.

How the three relate: the industry pages answer "what is commonly used on this equipment", the selector filters by parameters, and this page explains why the filtering works that way. None repeats another. Once a model is chosen and price and delivery come up, see commercial terms.

Two of the three models compared in the example can be opened directly: 6205 and 6305 (6005 follows the same structure and is reachable by switching series on either page).