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
- Ground
- Where a tolerance is tighter than turning holds reliably
- 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
- Bronze bush
- Fitted rather than applied · a material decision as much as a finish
Illustrative finish reference
| Finish | Typical use | What it changes |
|---|---|---|
| As machined | Hidden internal parts | Nothing |
| Ground | Bearing seats and fits | Dimension, by microns |
| Bead blasted | Visible covers and brackets | Dimension, by microns |
| Anodised | Aluminium that is handled | Dimension and colour |
Why the finish is specified with the datum.
Because a coating changes the dimension of the feature the datum is taken from. An anodised bore is smaller than the bore that was cut, and a drawing that does not say when it is measured 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.