Listed below you will find the standard industry values for a number of different dimensions that are measured for compliance when we produce your aluminum investment casting. Requested variations from standard practice usually result in a more expensive process and product. If at all possible, it is a very good idea to stay within standard practices for any casting you would have Nu-Cast produce for you.
Radii
As a general rule, a 0.03 maximum corner and a 0.06 minimum fillet are recommended. Smaller radii are possible depending on the complexity of the design.
Angles
Angular tolerances of +/-1/2 degree are normal.
Flatness and Straightness
When a high degree of flatness and straightness is required, castings must be mechanically straightened; however, proper design can control distortion and minimize straightening functions. Flatness and straightness tolerances are .003 to .005 TIR per linear inch and depend on alloy properties and configurations of part.
Hole Tolerances
The hole tolerances for round, square and D-holes are:
| Diameter: (inches) |
Tolerance: (inches) |
|---|---|
| up to .250″ I.D. | +/-.003 |
| .250″ to .500″ I.D. | +/-.004 |
| over .500″ I.D. | +/-.005 |
Surface Finish
NAS 823 visual comparison. Normal-125 Ra Premium-63 Ra
Draft
Generally draft allowance can be disregarded .
Roundness
The general linear tolerances can be held for diameter.
Concentricity
The general section thickness tolerances will prevail.