General Tolerances
These tolerances apply as a general rule of thumb. Closer tolerances can be obtained depending on part design or the use of special procedures or secondary operations.
Straightness
Tolerances for axial straightness: ±.005"/inch as cast.
Angles
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.
Blind Holes
Blind holes can be cast if length does not exceed the diameter. In nonferrous materials, blind holes under 2" may be cast if length does not exceed twice the diameter.
Hole Positioning
0.127 mm per 25 mm from any single reference point.
Tolerances
Concentricity
METRIC | |||
Range of nominal dimension (mm) | For Roundness / Concentricity (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 |
Surface Finish
Average Ra value generally ranges between 60 – 125 RMS
| Metal | Average RMS Value |
| Aluminium | 60-100 |
| Copper Alloys | 60-100 |
| Cobalt Chrome | 80-100 |
| 300 Series Stainless | 90-125 |
| Carbon Steel | 90-125 |
| 400 Series Stainless | 100-125 |
Round Hollow Tubing
Tubular section out of-roundness may be altered mechanically according to wall thickness and ductility. Tolerances are as follows:
| Diameter | Tolerances |
| Up to 1″ | 0.006″ TIR |
| 1″ to 11⁄2″ | 0.008″ TIR |
| 11⁄2″ to 2″ | 0.010″ TIR |
| 2″ to 3″ | 0.015″ TIR |
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 |
Casting Tolerances
METRIC | |
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 |