d, outer-ring diameter below the flange D, width B, flange OD Df and flange thickness Bf. The housing bore is machined to D, never to Df. The full size chart is on the flanged miniature bearings page.When a flange is the right choice
A flange is one of four common ways to fix the outer ring axially. It saves machining a shoulder in the housing, which matters most in thin walls, sheet-metal brackets and plastic housings.
| Locating method | Housing machining | What locates the other side | Watch out for |
|---|---|---|---|
| Flanged outer ring | Straight through-bore to D | Retaining ring, cover or a second bearing | Df and Bf differ between brands; the flange is thin |
| Shoulder in the housing | Stepped bore | Retaining ring or cover | Extra machining; shoulder height and corner radius must suit the bearing |
| Snap ring on the outer ring | Through-bore plus a recess for the ring | Retaining ring or cover | Needs a bearing with a ring groove |
| Cover or retaining ring only | Through-bore plus groove or cover seat | Second cover or ring | More parts; axial play depends on the stack-up |
How to measure an unknown flanged bearing
- Clean the bearing. Grease and rust change readings by more than a miniature tolerance.
- Measure the bore
dwith the inside jaws of a calibrated caliper, in more than one direction. - Measure
Don the cylindrical part of the outer ring, below the flange. Do not measure across the flange. - Measure the flange OD
Dfand the flange thicknessBf. - Measure the total width
B, flange included. Note whether there are metal shields (ZZ) or rubber seals (2RS): in miniature sizes the shielded version is often wider. - Look the size up on the flanged bearing size chart by
d,DandB, then confirmDfandBf.
The D-versus-Df trap
When a worn or unmarked flanged bearing is measured across the flange, the reading is Df, not D. A search with that value returns the wrong series or nothing. The table shows how far apart the two values are for common sizes.
| Model | d | D | Df | B | Bf |
|---|---|---|---|---|---|
| F692 ZZ | 2 | 6 | 7.5 | 3 | 0.8 |
| F623 ZZ | 3 | 10 | 11.5 | 4 | 1 |
| F683 ZZ | 3 | 7 | 8.1 | 3 | 0.8 |
| F693 ZZ | 3 | 8 | 9.5 | 4 | 0.9 |
| F684 ZZ | 4 | 9 | 10.3 | 4 | 1 |
| F685 ZZ | 5 | 11 | 12.5 | 5 | 1 |
| F695 ZZ | 5 | 13 | 15 | 4 | 1 |
| F625 ZZ | 5 | 16 | 18 | 5 | 1 |
| F688 ZZ | 8 | 16 | 18 | 5 | 1.1 |
| F698 ZZ | 8 | 19 | 22 | 6 | 1.5 |
| F608 ZZ | 8 | 22 | 25 | 7 | 1.5 |
| MF63 ZZ | 3 | 6 | 7.2 | 2.5 | 0.6 |
| MF74 ZZ | 4 | 7 | 8.2 | 2.5 | 0.6 |
| MF85 ZZ | 5 | 8 | 9.2 | 2.5 | 0.6 |
| MF105 ZZ | 5 | 10 | 11.6 | 4 | 0.8 |
| MF128 ZZ | 8 | 12 | 13.6 | 3.5 | 0.8 |
| MF148 ZZ | 8 | 14 | 15.6 | 4 | 0.8 |
Dimensions in mm, from the NLHB flange dimension table (same values as each model page). Flange sizes can differ between manufacturers for the same designation.
When the catalog has no flanged version
Some plain miniature sizes have no flanged counterpart. Example: MR42 ZZ is 2 × 4 × 2 mm in our dataset, and our flange table has no flanged bearing with a 2 mm bore and a 4 mm outside diameter. The nearest catalog flanged sizes have a 5 mm outside diameter.
| Route | What changes | Check before you choose |
|---|---|---|
| Use the nearest catalog flanged size, for example F682 ZZ (2 × 5 × 2.3, Df 6.1) or MF52 ZZ (2 × 5 × 2.5, Df 6.2) | The housing bore grows from 4 to 5 mm | Whether the housing wall and the space around it allow the larger bore |
| Custom outer ring with an integral flange | New ring drawing; the flange is formed in the ring blank before heat treatment and grinding | Drawing, sample, inspection report, lead time and quantity. A flange cannot be machined onto a finished plain outer ring: there is no material left. |
| Plain bearing in a flanged sleeve | The sleeve wall enlarges the mounting envelope | A press fit can distort a thin outer ring. Check clearance and running torque after fitting. |
| Keep the plain bearing and locate it with the housing | A shoulder, cover or retaining ring does the job of the flange | Housing machining and part count |
Which route fits depends on the space you have, the quantity and what the flange must do. Send the drawing first; we confirm feasibility, tooling and lead time before quoting.
What to put on a flanged bearing inquiry
- d, D, B, Df and Bf, with the tolerances you need and which dimension is the mounting reference.
- Shields or seals (ZZ, 2RS or open) and whether both sides need them.
- Material: chrome steel or stainless steel (the S prefix, for example SF or SMF).
- Internal clearance or preload, running-torque or noise requirements, and the grease.
- Speed, radial load and any axial load that passes through the flange.
- A sketch or photo of the mounting, the first-order quantity and the expected annual demand.
Checks on flanged samples
- Bore, outer-ring diameter, total width, flange OD and flange thickness against the signed drawing.
- Flange face runout to the outer-ring axis, and the flange root: no cracks, burrs or undercut damage.
- Clearance and starting and running torque after the bearing is fitted in the real housing, not only in free state.
- Shield-to-ring clearance: no rubbing after the shields are fitted.
- A run at the real speed, load and temperature: temperature rise, noise, grease leakage and wear.
Frequently asked questions
Can a flanged bearing go into a housing without a shoulder?
Yes. That is what the flange is for. The other axial direction still needs a retaining ring, cover or a second bearing.
How much axial load can the flange take?
It depends on the size, the flange thickness and how the load is applied. Treat the flange as a locating feature, and check any steady axial load through it with the supplier for your design.
Are F and SF bearings interchangeable?
They share boundary dimensions in our tables, but the material differs and the load ratings differ. Check the model page of the exact version.
Is the flange OD the same across brands?
Not always. Df and Bf come from each manufacturer's catalog. Confirm them on the drawing before you machine the housing.
Sources and data boundary
- NLHB flange dimension table and catalog dataset, checked November 1, 2026: flanged miniature bearings size chart.
- NLHB model pages for each designation (dimension drawing and load ratings).
Catalog values support identification and design. They do not replace the supplier's drawing or a sample check.