Investment casting produces parts with better accuracy than sand casting but typically looser than MIM or CNC machining. Understanding what is achievable — and what drives dimensional variation — helps set realistic specifications.
Investment casting tolerance by feature size:
| Dimension |
Typical Tolerance |
Best Achievable |
Equivalent IT Grade |
| < 25 mm |
±0.13-0.25 mm |
±0.10 mm |
IT8-IT10 |
| 25-50 mm |
±0.25-0.50 mm |
±0.18 mm |
IT9-IT11 |
| 50-100 mm |
±0.50-1.00 mm |
±0.35 mm |
IT10-IT12 |
| 100-200 mm |
±1.00-2.00 mm |
±0.70 mm |
IT11-IT12 |
Comparison with other processes:
| Process |
Typical Tolerance |
Surface Finish Ra |
Best For |
| Investment Casting |
±0.5% of dimension |
3.2-6.3 µm |
Complex shapes, moderate volume, wide material range |
| MIM |
±0.3% of dimension |
1.6-3.2 µm |
Small parts, high volume, tight tolerances |
| CNC Machining |
±0.013 mm |
0.4-1.6 µm |
Any size, low volume, tightest tolerances |
| Sand Casting |
±1.0-2.5% |
6.3-25 µm |
Large parts, low cost, loose tolerances |
| Die Casting |
±0.5-1.5% |
1.0-4.0 µm |
High volume, aluminum/zinc |
Factors affecting investment casting accuracy:
| Factor |
Variation Contribution |
Mitigation |
| Wax pattern shrinkage |
0.5-2.0% |
Use stabilized wax, controlled storage conditions |
| Wax pattern distortion |
0.1-0.5% |
Proper pattern support during storage, minimize handling |
| Shell expansion |
0.1-0.3% |
Consistent shell building process, controlled drying |
| Metal solidification shrinkage |
0.5-2.0% |
Alloy-specific shrinkage compensation in wax die design |
| Shell/metal reaction |
0.05-0.2% |
Proper shell chemistry for the alloy being poured |
Quick Q: What tolerance can investment casting achieve?
Investment casting typically holds ±0.5% of the dimension linearly. For a 25 mm part, expect ±0.13 mm. For a 100 mm part, expect ±0.50 mm. The best achievable tolerance is approximately ±0.3% with optimized tooling and process control. Investment casting is more accurate than sand casting (±1.0-2.5%) but less accurate than MIM (±0.3%) or CNC machining (±0.013 mm).