DEMO — fictional range. Local brief only, NOT SENT. No personal data is collected or transmitted.
FINISH
A finish is a functional decision that happens to be visible.
Surface finish is chosen for what the surface has to resist, then checked for how it looks. Chosen the other way round, it becomes an expensive way to hide a handling problem.
- As machined
- Tool marks left as cut · the cheapest option and honest about what it is
- Bead blasted
- A uniform matt surface · hides tool marks, changes the dimension slightly
- Clear anodised
- Corrosion resistance with the metal visible · bright anodising shows every mark
- Satin anodised
- The same protection with a softer appearance · the usual choice for handled parts
- Passivated
- For stainless · removes free iron from the surface after machining
- Zinc plated
- For steel · protection that is consumed over time rather than permanent
Illustrative finish reference
| Finish | Typical use | What it changes |
|---|---|---|
| As machined | Hidden internal parts | Nothing |
| Bead blasted | Visible covers and brackets | Dimension, by microns |
| Anodised | Aluminium that is handled | Dimension and colour |
| Passivated | Stainless after machining | Corrosion behaviour only |
Why the finish is specified with the tolerance.
Because most finishes change the dimension. An anodised bore is smaller than the bore that was cut, and a drawing that specifies H7 and a coating without saying which is measured when is a drawing that will be argued about.
The one worth avoiding.
Bright anodising on a part that will be handled. It shows every mark from the moment it leaves the anodising line, and the complaint arrives long after the finish was chosen.