Tolerances

Tolerances

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.

Straightness

Tolerances for axial straightness: ±.005"/inch as cast.

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.

Blind Holes

Blind holes can be cast if length does not exceed the diameter. In nonferrous materials, blind holes under 2" may be cast if length does not exceed twice the diameter.

Hole Positioning

0.127 mm per 25 mm from any single reference point.

Surface Finish

Average Ra value generally ranges between 60 - 125 RMS

Metal                Average RMS Value
 Aluminium 60-100
Copper Alloys 60-100
Cobalt Chrome 80-100
300 Series Stainless 90-125
Carbon Steel 90-125
400 Series Stainless 100-125

 

Round Hollow Tubing

Tubular section out of-roundness may be altered mechanically according to wall thickness and ductility. Tolerances are as follows:

Diameter Tolerances
Up to 1"  0.006" TIR
 1" to 11⁄2"  0.008" TIR
 11⁄2" to 2"  0.010" TIR
 2" to 3"  0.015" TIR

 

Casting Tolerances

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

 

METRIC

  Range of nominal dimension (mm)

  For Roundness / Concentricity (mm)

Over

Upto

As cast TIR

Machined TIR

   0

  10

  0.12

  0.08

  20

  25

  0.15

  0.10

  25

  50

  0.25

  0.15

  50

  75

  0.40

  0.25

  75

 100

  0.50

  0.35

 100

 150

  0.70

  0.45

 150

 200

  0.85

  0.55

 200

 300

  1.00

  0.70