GENERAL TOLERANCES

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GENERAL TOLERANCES

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:
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
 
 
 
 
 
 
 
 
 
 
 
 
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
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CONCENTRICITY:
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.