Why Billet, Not Cast
Production turbo housings are cast, which is efficient at volume. But for a one-off, a prototype, an odd size, or a discontinued unit, casting tooling is uneconomic — and a billet housing is denser, with no porosity, and can be made to a tighter, more repeatable finish. The catch is the geometry: a compressor housing is a spiral volute that grows in cross-section around the wheel, blended into inlet and outlet bores and a precise wheel-clearance contour. That's genuine 5-axis work.
The critical feature: the contour bore that sits around the compressor wheel. Its diameter and profile set the tip clearance — too tight and it rubs, too loose and it leaks efficiency. This is the dimension that decides whether the housing works.
How It Was Made
1 — Model the volute and clearances
The internal volute path, the wheel-clearance contour, and the inlet/outlet interfaces were defined as a 3D model. Where the housing had to match an existing turbo or wheel, those mating dimensions were measured and used as the reference — the same method as our reverse engineering service.
2 — 5-axis machine from solid
The housing was machined from a solid block of aluminium. 5-axis access lets a single setup reach the curved volute walls and blended transitions that a 3-axis machine simply can't, while holding the wheel-clearance contour to size. Machining from solid also means no draft angles or shrinkage to compensate — the model is the part.
3 — Polish to a mirror finish
The shell was finished and polished to the mirror surface seen here — partly cosmetic, partly because a smooth internal flow path matters on a compressor housing. Material is matched to the application; see aluminium machining.
The Workflow
Model volute & clearance
Internal volute and wheel-clearance contour defined; mating dimensions confirmed.
5-axis rough & finish
Curved walls and bores machined from solid billet in multi-axis setups.
Verify wheel clearance
Contour bore measured against the compressor wheel / spec before finishing.
Polish & inspect
Mirror-polished and final-inspected, ready to assemble.
Outcome
A complex internal-flow housing produced as a single billet part — no casting tooling, no porosity, and a finish a casting can't match. It's a clear example of where 5-axis machining earns its place: parts whose function lives in a curved internal surface. We apply the same approach across automotive performance parts and industrial equipment.
Need a billet housing or volute part? Send the turbo, the wheel, or your model and target clearances. We machine it from solid on 5-axis. Email [email protected] or message us on WhatsApp.