Oil-impregnated sintered bushings are supplied in two fundamental geometries: the plain cylindrical sleeve and the flanged (collared) bush. Both are pressed and sintered from a porous metal matrix and vacuum-impregnated with lubricating oil, so they share the same self-lubricating, maintenance-free running behaviour. The difference is purely mechanical — how the bush locates in its housing and which direction of load it can react. Getting the choice right at the design stage avoids axial float, thrust-face wear and unnecessary machining later.
The cylindrical bush: radial load, minimum envelope
A cylindrical bush is a straight sleeve defined by three dimensions: bore (Ø Int.), outside diameter (Ø Ext.) and length (Long.). It reacts radial load only and relies entirely on its interference fit in the housing to stay put. With no collar, it occupies the smallest possible envelope and is the default choice wherever a shaft simply needs a low-friction journal.
The Bushingo cylindrical range is deliberately broad. The BP25 sintered-bronze family alone spans bores from Ø Int. 2 – Ø Ext. 5 – Long. 2 at the small end (the 02–15 group, 97 sizes) up to Ø Int. 125 – Ø Ext. 150 – Long. 120 in the 35–125 group. The FP20 sintered-iron equivalent covers 91 sizes, from Ø Int. 3 – Ø Ext. 6 – Long. 4 to Ø Int. 100 – Ø Ext. 120 – Long. 120. Note how the wall stays modest — (Ø Ext. − Ø Int.)/2 is frequently 1.5, 2 or 3 mm — which keeps the porous section thin so oil reaches the bore quickly by capillary action.
The flanged bush: radial plus axial location
A flanged bush adds an integral collar at one end. Its size chart carries two extra parameters: the collar diameter (Ø Coll.) and the flange thickness (Ép.). That collar does two jobs. First, it locates the bush axially — the flange seats against the housing face and stops the bush creeping through under vibration. Second, it provides a thrust surface, letting the bush carry light axial load alongside the radial journal load.
A representative flanged size from the BP25 bronze range is Ø Int. 22 – Ø Ext. 28 – Long. 25 – Ø Coll. 34 – Ép. 3: a 22 mm bore sleeve with a 34 mm collar 3 mm thick. The C03–C20 group offers 68 fine-pitch sizes from Ø Int. 3 upward; the C22–C60 group adds 59 larger sizes up to Ø Int. 60 – Ø Ext. 70 – Long. 60 – Ø Coll. 80 – Ép. 5; and a dedicated FP20 sintered-iron flanged family provides a further 52 sizes for the same duty in a harder, lower-cost matrix.
Choosing between them
The decision is driven by how the shaft is located and loaded. If axial position is fixed elsewhere in the assembly and the bush sees radial load only, the cylindrical sleeve is lighter, cheaper and more compact. If the bush must also stop the shaft moving axially, take a thrust reaction, or resist being pushed through its housing — common on vertical shafts and pivot pins — the flange earns its place.
| Feature | Cylindrical bush | Flanged bush |
|---|---|---|
| Load direction | Radial only | Radial plus light axial / thrust |
| Axial location | By interference fit alone | Positive, via seated flange |
| Envelope | Minimum | Needs clearance for the collar |
| Extra chart dimensions | — | Ø Coll., Ép. |
| Typical use | Journals, linkage pivots, guide rails | Vertical shafts, combined journal and thrust, anti-push-through |
Material choice runs across both geometries
BP25 sintered bronze and FP20 sintered iron are offered in both flanged and cylindrical form, so geometry and material are independent decisions. Bronze is the general-purpose choice, with good conformability, corrosion resistance and quiet running. Iron is harder and more economical, well suited to heavier, slower, intermittent duty where cost matters. Whichever you pick, the porous matrix carries roughly 20–25% interconnected porosity filled with oil, and sintered bronze bushings of this type typically run to around 100 °C continuously before oil viscosity and oxidation become limiting. Treat such figures as characteristic of the material class, not as a certified rating for a specific size.