 |
PROCESS : TECHNICAL SPECIFICATION : 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. |
CASTING TOLERANCE |
Metrics |
Upto 25 mm |
± 0.127 mm |
Upto 50 mm |
± 0.254 mm |
Upto 75 mm |
± 0.381 mm |
Upto 100 mm |
± 0.508 mm |
Upto 125 mm |
± 0.635 mm |
Upto 150 mm |
± 0.762 mm |
|
FLATNESS |
Flatness refers to single plane surface and is usually a function of volumetric
shrinkage |
Metrics |
Range of nominal dimension (mm)
|
For starightness / flatness (mm)
|
Over |
Upto
|
0 |
10 |
20 |
25 |
25 |
50 |
50 |
75 |
75 |
100 |
100 |
150 |
150 |
200 |
200 |
300 |
|
As Cast TIR |
Machined TIR
|
0.12 |
0.08 |
0.15 |
0.10 |
0.20 |
0.15 |
0.30 |
0.20 |
0.40 |
0.25 |
0.55 |
0.35 |
0.70 |
0.50 |
0.95 |
0.70 |
|
|
CONCENTRICITY |
Metrics |
Range of nominal dimension (mm)
|
for Roundness / Concentricity (mm)
|
Over |
Upto
|
0 |
10 |
20 |
25 |
25 |
50 |
50 |
75 |
75 |
100 |
100 |
150 |
150 |
200 |
200 |
300 |
|
As Cast TIR |
Machined TIR
|
0.12 |
0.08 |
0.15 |
0.10 |
0.20 |
0.15 |
0.30 |
0.20 |
0.40 |
0.25 |
0.50 |
0.35 |
0.85 |
0.55 |
1.00 |
0.70 |
|
|
ROUNDNESS - SOLID BARS |
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. |
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. |
HOLE POSITIONING |
0.127 mm per 25 mm from any single reference point. |
BLIND HOLES |
Blind holes can be cast if length does not exceed the diameter |
SURFACE FINISH |
Average Ra value generally ranges between 3.20 to 5.50 microns |