Self-aligning ball bearing · 12 series
1203 bearing
17 × 40 × 12 mm
The 1203 is a self-aligning ball bearing with a 17 mm bore, 40 mm outside diameter and 12 mm width. Light series, same envelope as 62xx.
- Bore d
- 17 mm 0.6693 in
- Outside diameter D
- 40 mm 1.5748 in
- Width B
- 12 mm 0.4724 in
- Dimension series
- 02
- Load directions
- Mainly radial; light axial
Designation explained
What 1203 means
Standard bearing numbers encode the type, the dimension series and the bore. Anything after the base number — seals, clearance, cage — is a suffix.
| Part | Meaning |
|---|---|
1 | Self-aligning ball bearing |
2 | Diameter series 2, dimension series 02 |
03 | 03 → 17 mm bore (fixed code for small bores) |
Variants
Common 1203 variants
Suffixes change the bearing without changing its boundary dimensions. The exact letters differ between manufacturers — always order by the full designation from the maker you choose.
| Suffix | Example | Meaning |
|---|---|---|
K | 1203K | Tapered bore (taper 1:12) for mounting on an adapter or withdrawal sleeve |
2RS | 1203-2RS | Contact seals on both sides (available for selected sizes; may be wider) |
TV / TN9 / M | 1203-TVH | Cage material: polyamide (TV, TN9) or machined brass (M) — letters vary by maker |
CN (no suffix) | 1203 | Normal internal clearance |
C3 | 1203-C3 | Internal clearance greater than normal — common for electric motors and heated shafts |
C4 | 1203-C4 | Internal clearance greater than C3 |
Same envelope
Same 17 × 40 × 12 mm, different type
These bearings have exactly the same bore, outside diameter and width but are a different type. They fit the same housing and shaft, but carry loads differently — same size is not the same function.
Same bore
Other 17 mm bore bearings
Every standard bearing in this reference with a 17 mm bore, from light to heavy sections.
| Designation | Type | D | B / H |
|---|---|---|---|
| 6003 | Deep groove ball bearing | 35 mm | 10 mm |
| 6303 | Deep groove ball bearing | 47 mm | 14 mm |
| 6403 | Deep groove ball bearing | 62 mm | 17 mm |
| 61803 | Deep groove ball bearing | 26 mm | 5 mm |
| 61903 | Deep groove ball bearing | 30 mm | 7 mm |
| 16003 | Deep groove ball bearing | 35 mm | 8 mm |
| 1303 | Self-aligning ball bearing | 47 mm | 14 mm |
| 2203 | Self-aligning ball bearing | 40 mm | 16 mm |
| 2303 | Self-aligning ball bearing | 47 mm | 19 mm |
| 7303 | Angular contact ball bearing | 47 mm | 14 mm |
| 30203 | Tapered roller bearing | 40 mm | 13.25 mm |
| 30303 | Tapered roller bearing | 47 mm | 15.25 mm |
| 51103 | Thrust ball bearing | 30 mm | 9 mm |
| 51203 | Thrust ball bearing | 35 mm | 12 mm |
| UCP203 | Pillow block bearing unit | — | — |
Where to buy
Find 1203 at sellers
Search results on independent sellers. We are not affiliated with them, do not earn from these links and do not see their prices or stock. Results mix brands and variants — check the full designation before you order.
About these dimensions. Boundary dimensions follow ISO 15 (radial bearings — boundary dimensions, general plan), dimension series 02, and are the same for every manufacturer of a standard 1203. Chamfers, load ratings, speed limits and weight depend on the manufacturer and design and are not shown — use the maker's datasheet for engineering decisions. Last checked 9 October 2026. Spotted an error? Tell us.
Learn more
What size is a 1203 bearing?
A 1203 is a self-aligning ball bearing with a 17 mm bore, 40 mm outside diameter and 12 mm width (17 × 40 × 12 mm). These boundary dimensions follow the ISO dimension plan, so they are the same across manufacturers.
Can I replace 1203 with another bearing of the same size?
Other bearing types can share the same 17 × 40 × 12 mm envelope, but a different type has different load directions, speed limits and mounting needs. Same dimensions alone do not make two bearings interchangeable.
Where are the load ratings and speed limits?
They depend on the manufacturer and internal design, so we do not list a single value. Check the datasheet for the exact full designation you intend to use.
Need 1203 data for a whole catalog?
We can help with that.
Normalized specifications, variants and supplier listings for every bearing you sell, with the source behind each value.