A maintenance buyer gets a parts list: SKF 6205-2RSH/C3, NSK 6305DDU, Timken 30206 and a few pillow block units. The task is to find the same sizes from another source without causing a fit problem on the shop floor. Most of the answer is already in the part number, once you know which parts of it are standard and which belong to the maker.
The basic number is standard
For metric radial bearings, ISO 15 fixes the boundary dimensions for each basic number: bore, outside diameter and width. A 6205 is 25 mm bore, 52 mm outside diameter and 15 mm wide at every maker that follows the standard. Metric tapered roller bearings follow ISO 355 in the same way, so a 30206 is 30 × 62 × 17.25 mm whoever made it.
The last two digits are the bore code. From 04 upward, multiply by 5 to get the bore in millimetres: 05 is 25 mm, 08 is 40 mm. Below that, 00 to 03 mean 10, 12, 15 and 17 mm.
The suffix is where brands differ
After the basic number, each maker writes seals, shields and internal clearance its own way. For a 6205:
| Design | SKF | NSK | Timken | FULI |
| Open | 6205 | 6205 | 6205 | 6205 |
| Metal shields, both sides | 6205-2Z | 6205ZZ | 6205-ZZ | 6205ZZ |
| Rubber contact seals, both sides | 6205-2RSH | 6205DDU | 6205-2RS | 6205-2RS |
| Contact seals, C3 clearance | 6205-2RSH/C3 | 6205DDUC3 | 6205-2RS-C3 | 6205-2RS C3 |
All of these are 25 × 52 × 15 mm. The table only says the parts fit the same space. It says nothing about how one maker’s bearing compares with another’s.
Five places where cross-referencing goes wrong
- Contact and non-contact seals. NSK DDU and NTN LLU are rubber contact seals. NSK VV and NTN LLB are non-contact seals. Both are “sealed”, but they differ in friction and in how well they keep out dust and water. Match the seal type, not just the word.
- Clearance dropped on the way. A /C3 or C3 at the end of the number means more internal clearance than normal, common on electric motor bearings that run warm. If the suffix gets lost while a list is retyped, the replacement arrives with normal clearance.
- Tapered roller prefixes and suffixes. The basic number stays, but the makers add their own design codes: NSK HR30206J, NTN 4T-30206, Koyo 30206JR, and SKF orders it as 30206 J2/Q. These mark design and cage, not seals. Two sizes need care. SKF sells 32205 only as 32205 BJ2/Q, with a larger contact angle than the standard design. On 30304, the cone width is 15 mm at some makers and 16 mm at others, even though bore, outside diameter and total width match.
- Inch tapered bearings come in two parts. Timken’s inch series uses separate numbers for the cone and the cup, for example an LM11949 cone with an LM11910 cup. A list that gives only one number is asking for only one part. Confirm whether the buyer needs the cone, the cup or both.
- Mounted units: the insert matches, the housing may not. On a UCP205, the UC205 insert interchanges between makers. The housing is a separate check. The JIS version of UCP204 has a bolt spacing of 95 mm, while ISO 3228 housings of that size use 96 mm. The writing also varies: NTN and NSK add D1 (UCP205D1), and SKF writes a space (UCP 205). US inch units from Dodge or SealMaster use their own numbering, so match the centre height and bolt spacing as well as the shaft size.
What a cross reference does not cover
A matching number confirms the boundary dimensions. Load ratings, speed limits, cage material, grease type and fill, vibration grade and steel are each maker’s own data. Put those on the request for quotation as line items, and compare the supplier’s figures against what the application needs.
What to send with a cross-reference request
- The brand and the full part number, with every prefix and suffix, for example SKF 6205-2RSH/C3.
- The quantity for each line.
- What the bearing is used in, if you know.
- A photo of the markings on the old bearing when the number is worn or partly missing.
At FULI Bearings, we check each line of a cross-reference list against these points before we quote. To match one maker’s number to another’s, we start with the printed interchange handbooks and then check the result online. Our FULI bearing cross-reference tables set the SKF, FAG, Timken, NSK, NTN, Koyo and NACHI forms next to the FULI number for deep groove ball, tapered roller and spherical roller bearings and for UC pillow block units.
A correct suffix match is not the same as the right bearing for the job. In 2004 a customer in Singapore ordered cylindrical roller bearings with C4 clearance. After the bearings shipped, C4 proved wrong for the actual use: the clearance was too large for that equipment. Copying a suffix such as C4 from a list is not enough; check it against what the bearing does.
A few minutes spent on the suffix before the order is placed saves a shipment of bearings that fit the shaft but not the job.
SKF, NSK, NTN, Timken, Koyo, FAG, NACHI, Dodge and SealMaster are trademarks of their respective owners. Part numbers are shown for interchange reference only.
