Flanged bearings explained: what the F in F623ZZ means
An F in front of a bearing number means a flange on the outer ring. Here is what the flange does, how to read flanged part numbers, and what to measure before you order.
A flanged bearing is an ordinary ball bearing with one change: a thin lip, or flange, around one side of the outer ring. That small lip changes how the bearing is fitted, and it is why a part number such as F623ZZ starts with an F.
What the flange does
A standard bearing sits in a housing bore with a shoulder or a circlip to stop it sliding through. A flanged bearing does not need either. You push it into a straight, through-bored hole until the flange meets the face of the housing, and the flange holds it in place.
That makes the housing simpler and cheaper to machine, and it is why flanged bearings are common in pulleys and idler rollers, 3D printers and CNC machines, small conveyors, office machines and robotics.
How to read a flanged part number
The F is added in front of the standard number. Everything else keeps its usual meaning:
- F623ZZ: a flanged 623 with metal shields on both sides. Bore 3 mm, outside diameter 10 mm, width 4 mm.
- FMR106ZZ: a flanged MR106 miniature bearing, 6 × 10 × 3 mm. See our MR bearing size guide for how MR numbers work.
- F6001ZZ: a flanged 6001, 12 × 28 × 8 mm.
- SSF608ZZ: a stainless steel flanged 608, 8 × 22 × 7 mm, for wet or washdown areas.
The seal codes are the same as on any bearing: ZZ for metal shields, 2RS for rubber seals, and no letters for an open bearing. Read ZZ or 2RS? if you are not sure which you need.
Flanged sizes we supply
| Part number | Bore (mm) | Outside diameter (mm) | Width (mm) |
|---|---|---|---|
| F623ZZ | 3 | 10 | 4 |
| F695ZZ | 5 | 13 | 4 |
| FMR106ZZ | 6 | 10 | 3 |
| F686 | 6 | 13 | 3.5 |
| SSF608ZZ | 8 | 22 | 7 |
| F6000ZZ | 10 | 26 | 8 |
| F6001ZZ | 12 | 28 | 8 |
| F6704ZZ | 20 | 27 | 4 |
| F6904ZZ | 20 | 37 | 9 |
| F6905ZZ | 25 | 42 | 9 |
| F6005ZZ | 25 | 47 | 12 |
Bore, outside diameter and width are the same as the standard bearing without a flange. All are available – ask for stock, in multiple brands.
What to measure before you order
For a flanged bearing you need five measurements, not three. Use a vernier or digital caliper:
- Bore: the hole in the inner ring.
- Outside diameter: across the body of the outer ring, not across the flange.
- Width: the overall width of the outer ring.
- Flange diameter: across the flange.
- Flange thickness: the thickness of the lip itself.
The flange diameter and thickness are not part of the bearing number, and they can differ slightly between sizes and makers. If the flange must fit a recess or sit against a close part, send us both measurements and we will match them. Our guide on how to measure a bearing covers the other three.
Fitting tips
- Press the bearing in by the outer ring, never by the inner ring or the shields, until the flange sits flat against the housing face.
- The flange locates the bearing in one direction only. If there is any axial load pushing the other way, the other side still needs a retaining ring, a spacer or a second flanged bearing facing the opposite way.
- A flanged bearing cannot normally be swapped for a plain one, because a through-bored housing has no shoulder to hold a plain bearing in place.
Looking for a flanged size that is not listed?
Send us the five measurements, or a photo of the old bearing next to a ruler, on WhatsApp. You can also browse all our part numbers or the bearing size chart.