Casting Tolerances per. NADCA and ISO

Manufacturing Processes | Mechanical Tolerances

The North American Die Casting Association (NADCA) has standard specifications for setting high pressure die casting tolerances. There is also the international ISO standard series, which focuses on casting tolerances. This series replaces the former ISO 8062:1994. ISO 8062:1994 did not have specifications to high pressure die castings.

ISO 8062-1…3 defines casting tolerances as DCT (Dimensional Casting Tolerance) grades and GCT (Geometrical Casting Tolerance) grades. The former ISO 8062 defined tolerances only as CT (Casting Tolerance) grades.

ISO 8062-1…3 consists of the following titles.

  • ISO 8062-1:2007 Geometrical product specifications (GPS) Dimensional and geometrical tolerances for molded parts.
  • ISO/TS 8062-2 Geometrical product specifications (GPS) Dimensional and geometrical tolerances for molded parts.
  • ISO 8062-3:2007 Geometrical product specifications (GPS) Dimensional and geometrical tolerances for molded parts Part 3: General dimensional and geometrical tolerances and machining allowances for castings

Per the NADCA specifications, high pressure die casting tolerances are divided into two groups: normal and precision tolerances. International ISO standard does not use these terms, but specifies the tightest geometrical tolerance grade as one to be used only by "special agreement". The precision tolerances may be more costly to achieve, because the die caster has to pay more attention to the thermal stability during casting cycles and also the die has to be more rigid and well tested. Usually rigidity requires thicker plates and these add to the die costs.

NADCA specifications cover the following high pressure die casting tolerances:

  • dimensional tolerance
  • angular tolerance, which includes flatness, parallelism and perpendicularity tolerances
  • concentricity tolerance
  • parting line shift tolerance
  • flatness tolerance

ISO 8062 covers the following tolerances:

  • dimensional tolerances
  • combined roundness, parallelism, perpendicularity and symmetry tolerance
  • concentricity tolerance
  • straightness tolerance − flatness tolerance

Dimensional tolerances cover tolerances for dimensions in one die half and dimensions over parting line. ISO 80623 standard asks to notice the dimensions over parting line, but does not give precise rules how.

NADCA dimensional tolerances, dimensions in one die half

Standard

Aluminum

Magnesium

Zinc

Copper

Normal

± 0,25 mm per 25 mm + additional ± 0,025 mm per each full 25 mm

± 0,36 mm per 25 mm + additional ± 0,076 mm per each full 25 mm

Precision

± 0,05 mm per 25 mm + additional ± 0,025 mm per each full 25 mm

± 0,18 mm per 25 mm + additional ± 0,05 mm per each full 25 mm

ISO 80623:2007 dimensional tolerances

Largest overall dimension

Aluminum

Magnesium

Zinc

Copper

≤ 50 mm

DCTG 6:

DCTG 3 – 6

DCTG 6 – 8

> 50 mm ≤ 180 mm

DCTG 7

> 180 mm ≤ 500 mm

DCTG 8

> 500 mm

DCTG 9

NADCA dimensional tolerances, dimension over parting line; normal (and precision) tolerances

Projected area of the casting

Zinc

Aluminum

Magnesium

Copper

65cm2

+0,114 mm (+0,076) mm

+0,14 mm (0,089) mm

+0,14 mm (+0,089) mm

+0,20 mm (+0,20) mm

65 – 130 cm2

+0,13 mm (+0,089) mm

+0,165 mm (+0,102) mm

+0,165 mm (+0,102) mm

+0,23 mm (+0,23) mm

130 – 325 cm2

+0,15 mm (+0,102) mm

+0,19 mm (+0,153) mm

+0,19 mm (+0,153) mm

+0,25 mm (+0,25) mm

325 – 650 cm2

+0,23 mm (+0,153) mm

+0,30 mm (+0,203) mm

+0,30 mm (+0,203) mm

-

650 – 1300 cm2

+0,30 mm (+0,203) mm

+0,46 mm (+0,305) mm

+0,46 mm (+0,305) mm

-

1300 – 1950 cm2

+0,46 mm (+0,305) mm

+0,61 mm (+0,406) mm

+0,61 mm (+0,406) mm

-

NADCA dimensional tolerances, dimension towards a moving core; normal (and precision) tolerances

Projected area of the casting

Zinc

Aluminum

Magnesium

Copper

65 cm2

+ 0,15 mm (+ 0,127) mm

+ 0,20 mm (0,152) mm

+ 0,20 mm (+ 0,127) mm

+ 0,12 mm (+ 0,254) mm

65 - 130 cm2

+ 0,23 mm (+ 0,178) mm

+ 0,33 mm (+ 0,254) mm

+ 0,33 mm (+ 0,178) mm

-

130 - 325 cm2

+ 0,33 mm (+ 0,254) mm

+ 0,48 mm (+ 0,356) mm

+ 0,48 mm (+ 0,254) mm

-

325 - 650 cm2

+ 0,48 mm (+ 0,356) mm

+ 0,61 mm (+ 0,457) mm

+ 0,61 mm (+ 0,356) mm

-

650 - 1300 cm2

+ 0,66 mm (+ 0,483) mm

+ 0,81 mm (+ 0,61) mm

+ 0,81 mm (+ 0,483) mm

-

1300 - 1950 cm2

+ 0,81 mm (+ 0,61) mm

+ 0,1 mm (+ 0,762) mm

+ 0,1 mm (+ 0,61) mm

-

Geometrical tolerances

Geometrical tolerances include straightness, flatness, combined roundness, parallelism, perpendicularity and symmetry tolerance, concentricity, parting line shift and flatness tolerance.

ISO 8062-3 straightness tolerance

Raw casting basic dimension (mm)
Geometrical casting tolerance grade GCTG for straightness
 

From

To

2: Only by special agreement

3: Common castings without back draft features with moving die components

4: Complex castings and castings with moving die components

10

0,08

0,12

0,18

> 10

30

0,12

0,18

0,27

> 30

100

0,18

0,27

0,4

> 100

300

0,27

0,4

0,6

> 300

1000

0,4

0,6

0,9

Calculated for the largest dimension, for example diameter, measure from corner to corner in the case of rectangular objects, etc.

ISO 80623 and NADCA flatness tolerances

Raw casting basic dimension (mm)
Geometrical casting tolerance grade GCTG for flatness
NADCA casting tolerance for flatness

From

To

Only by special agreement

Common castings without back draft features with moving die components

Complex castings and castings with moving die components

10

0,12

0,18

0,27

At the first 75 mm 0,20 mm + 0,08 mm after each additional 25 mm

> 10

30

0,18

0,27

0,4

> 30

100

0,27

0,4

0,6

> 100

300

0,4

0,6

0,9

> 300

1000

0,6

0,9

1,4

Tolerance mm

NADCA parting line shift tolerance

Projected area

Tolerance

< 325 cm2

± 0,102 mm

325 650 cm2

± 0,152 mm

650 1290 cm2

± 0,203 mm

1290 1940 cm2

± 0,279 mm

1940 3225 cm2

± 0,406 mm

3225 5160 cm2

± 0,508 mm

5160 7740 cm2

± 0,635 mm

ISO 80623:2007 combined tolerance for roundness, parallelism, perpendicularity and symmetry

Raw casting basic dimension (mm)

Only by special agreement

Common castings without back draft features with moving die components

Complex castings and castings with moving die components

From To

10

0,18

0,27

0,4

> 10

30

0,27

0,4

0,6

> 30

100

0,4

0,6

0,9

> 100

300

0,6

0,9

1,4

> 300

1000

0,9

1,4

2

Tolerance mm

NADCA angular tolerance (combined flatness, parallelism and perpendicularity tolerance)

Standard

Both surfaces in the same die half

Surfaces across the parting line or the other surface parting surface

Both surfaces in the same die half, the other surface is a moving core surface

Surfaces across the parting line or the other surface parting surface, tolerance towards a moving core surface

Normal

0,13 mm per 75 mm + 0,025 mm per each additional 25 mm

0,20 mm per 75 mm + 0,038 mm per each additional 25 mm

0,20 mm per 75 mm + 0,038 mm per each additional 25 mm

0,28 mm per 75 mm + 0,076 mm per each additional 25 mm

Precision

0,08 mm per 75 mm + 0,025 mm per each additional 25 mm

0,13 mm per 75 mm + 0,025 mm per each additional 25 mm

0,13 mm per 75 mm + 0,025 mm per each additional 25 mm

0,20 mm per 75 mm + 0,05 mm per each additional 25 mm

ISO 80623:2007 concentricity tolerances

Raw casting basic dimension (mm)

2: Only by special agreement

3: Common castings without back draft features with moving die components

4: Complex castings and castings with moving die components

From
To

10

0,27

0,4

0,6

> 10

30

0,4

0,6

0,9

> 30

100

0,6

0,9

1,4

> 100

300

0,9

1,4

2

> 300

1000

1,4

2

3

Tolerance mm

NADCA concentricity tolerances

Projected area

Both surfaces in the same die half

Surfaces across the parting line, additional tolerance

< 325 cm2

0,20 mm per 75 mm + 0,05 mm to each additional 25 mm

0,20 mm

325 - 650 cm2

0,30 mm

650 - 1290 cm2

0,41 mm

1290 - 1940 cm2

0,56 mm

ISO 8062:2007 Dimensional casting tolerance grades (DCTG)

The table presents the grades and dimension intervals, which are workable for high pressure die castings.

Raw casting basic dimension (mm)
Dimensional casting tolerance grade DCTG

From

To

1

2

3

4

5

6

7

8

9

10

10

±0,09

±0,13

±0,18

±0,26

±0,36

±0,52

±0,74

±1

±1,5

±2

10

16

±0,1

±0,14

±0,2

±0,28

±0,38

±0,54

±0,78

±1,1

±1,6

±2,2

16

25

±0,11

±0,15

±0,22

±0,3

±0,42

±0,58

±0,82

±1,2

±1,7

±2,4

25

40

±0,12

±0,17

±0,24

±0,32

±0,46

±0,64

±0,9

±1,3

±1,8

±2,6

40

63

±0,13

±0,18

±0,26

±0,36

±0,5

±0,7

±1

±1,4

±2

±2,8

63

100

±0,14

±0,2

±0,28

±0,4

±0,56

±0,78

±1,1

±1,6

±2,2

±3,2

100

160

±0,15

±0,22

±0,3

±0,44

±0,62

±0,88

±1,2

±1,8

±2,5

±3,6

160

250

±0,24

±0,34

±0,5

±0,7

±1

±1,4

±2

±2,8

±4

250

400

±0,4

±0,56

±0,78

±1,1

±1,6

±2,2

±3,2

±4,4

400

630

±0,64

±0,9

±1,2

±1,8

±2,6

±3,6

±5

630

1 000

±1

±1,4

±2

±2,8

±4

±6

1 000

1 600

±1,6

±2,2

±3,2

±4,6

±7

Tolerance ± mm

ISO 8062:1994 Casting tolerance grades (CTG)

The tolerance grade is described with CT. It varies depending on the casting method and also on used material and alloy. Normal high pressure die casting tolerance grade is CT 57 for aluminum and magnesium, CT 68 for copper and CT 46 for zinc.

Raw casting basic dimension (mm)
Casting tolerance grade CTG

From

To

4

5

6

7

8

9

10

11

12

13

14

0
10
0,26
0,36
0,52
1,00
1,5
2,0
2,8
4,2
-
-
10
16
0,28
0,38
0,54
0,78
1,10
1,6
2,2
3,0
4,4

16

25

0,30

0,42

0,58

0,82

1,20

1,7

2,4

3,2

4,6

6,0

8,0

25

40

0,32

0,46

0,64

0,90

1,30

1,8

2,6

3,6

5,0

7,0

9,0

40

63

0,36

0,50

0,70

1,00

1,40

2,0

2,8

4,0

5,6

8,0

10,0

63

100

0,40

0,56

0,78

1,10

1,60

2,2

3,2

4,4

6,0

9,0

11,0

100

160

0,44

0,62

0,88

1,20

1,80

2,5

3,6

5,0

7,0

10,0

12,0

160

250

0,50

0,70

1,00

1,40

2,00

2,8

4,0

5,6

8,0

11,0

14,0

250

400

0,56

0,78

1,10

1,60

2,20

3,2

4,4

6,2

9,0

12,0

16,0

400

630

0,64

0,90

1,20

1,80

2,60

3,6

5,0

7,0

10,0

14,0

18,0

630
1000
1,00
-
1,40
2,00
2,80
4,0
6,0
8,0
11,0
16,0
20,0
1000
1600
1,6
-
-
2,2
3,0
4,6
7,0
9,0
13,0
18,0
23,0

Tolerance ± mm

References
  • J. Campbell, Castings, 2 nd edition, Elsevier, UK, 2005
  • ISO 8062: 1994 Castings - System of dimensional tolerances and machining allowances
  • EN ISO 80623:2007 Geometrical Product Specifications (GPS). Dimensional and geometrical tolerances for molded parts. Part 3: General dimensional and geometrical tolerances and machining allowances for castings
  • Product Design for Die Casting, NADCA, USA 1998
  • Product Specification Standards for Die Castings, NADCA, USA, 2006
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