Centrifugal vs Sand Casting of Bronze: Which Process Fits Your Part?

The one-line rule: symmetric parts — bushings, rings, sleeves — suit centrifugal casting; anything with complex outer geometry suits sand casting.

Why centrifugal casting makes better bearing bronze

A bushing is a tube. Pour the molten metal into a mold spinning around the tube's axis and centrifugal force does two useful things: it packs metal into the outer wall where the bearing surface will be, and it pushes gas and inclusions inward, where they are machined off. The result is a dense, fine-grained structure with noticeably better mechanical properties than the same alloy sand-cast.

That is why loaded bushings are almost always centrifugal cast. If your part is essentially cylindrical and strength matters, the process pays for itself.

Where sand casting takes over

Sand casting has exactly one edge over centrifugal: complete freedom of external geometry — flanges, ribs, bosses, asymmetry, large sizes. For those parts, sand casting is the only practical process, and it usually wins on tooling cost for short runs.

Its weakness is the porosity and inclusions inherent to gravity pouring; mechanical properties sit below centrifugal castings, so heavily loaded bearings cast in sand are a compromise.

Metal-mold casting, the middle path

Pour into a permanent steel or iron mold and you get finer grain and better repeatability than sand, at a lower per-piece cost than centrifugal for short-cylindrical shapes like gear or flange blanks. It occupies a useful middle ground for medium runs.

How to choose — and how we build

We run all three processes in one foundry, so the judgment call is made on the part, not on capability. As a rule: bearing sleeves → centrifugal. Complex or large parts → sand. Standard medium-run round blanks → metal mold. Send a drawing and we will quote the right process, then machine the casting complete in our own CNC shop.

See how this plays out in production: Custom Cast Bronze Parts — centrifugal, sand and metal-mold casting with in-house CNC machining.