General Tolerances
Casting Tolerances
| Metric | |
|---|---|
| Meta Up to 25 mm | ± 0.127 mm |
| Up to 50 mm | ± 0.254 mm |
| Up to 75 mm | ± 0.381 mm |
| Up to 100 mm | ± 0.508 mm |
| Up to 125 mm | ± 0.635 mm |
| Up to 150 mm | ± 0.762 mm |
Flatness
Flatness refers to single plane surface and is usually a function of volumetric shrinkage
| Metric | |||
|---|---|---|---|
| Range of nominal dimension (mm) | For Straightness / Flatness (mm) | ||
| Over | Upto | As cast TIR | Machined TIR |
| 0 | 10 | 0.12 | 0.08 |
| 20 | 25 | 0.15 | 0.10 |
| 25 | 50 | 0.20 | 0.15 |
| 50 | 75 | 0.30 | 0.20 |
| 75 | 100 | 0.40 | 0.25 |
| 100 | 150 | 0.55 | 0.35 |
| 150 | 200 | 0.70 | 0.50 |
| 200 | 300 | 0.95 | 0.70 |
Concentricity
| Metric | |||
|---|---|---|---|
| Range of nominal dimension (mm) | For Straightness / Flatness (mm) | ||
| Over | Upto | As cast TIR | Machined TIR |
| 0 | 10 | 0.12 | 0.08 |
| 20 | 25 | 0.15 | 0.10 |
| 25 | 50 | 0.25 | 0.15 |
| 50 | 75 | 0.40 | 0.25 |
| 75 | 100 | 0.50 | 0.35 |
| 100 | 150 | 0.70 | 0.45 |
| 150 | 200 | 0.85 | 0.55 |
| 200 | 300 | 1.00 | 0.70 |
Roundness is a function of normal shrinkage variations in the metal. Shrinkage variation increases with diameter and the tolerance required increases proportionately. A general rule of 0.127 mm per 25 mm may be applied.
As-cast tolerances of angles depend on their location in casting. They range from ± 1/2° for well supported positions to ± 2° where inherent distortion could be expected. Inclusion of gussets and ribs often minimizes distortion and many sections can be mechanically straightened.
0.127 mm per 25 mm from any single reference point.
Blind holes can be cast if length does not exceed the diameter
Average Ra value generally ranges between 3.20 to 5.50 microns.