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