Technical Data - Standard Tolerances

Linear Tolerances, As Cast +

SIMPLE LINEAR TOLERANCES WHERE PARTING LINE NOT INVOLVED

The tolerance on a dimension "A" will be the value shown in the tables below. This tolerance will increase where the parting line of the die, or die moving parts affect the dimension.

Note that the values represent normal production practice at the most economical level. Greater accuracy should only be specified where required to avoid additional costs.

Tolerances for Critical dimensions in mm (One or two Decimal Places)

Length of Dimension "A" Zinc Aluminium Magnesium
Basic tolerance. Up to 25mm +/- 0.08 +/- 0.10 +/- 0.10
Additional tolerance for each additional 25mm.
Over 25 mm to 300 mm
+/- 0.03 +/- 0.04 +/- 0.04
Additional tolerance for each additional 25mm.
Over 300 mm
+/- 0.03 +/- 0.03 +/- 0.03

Tolerances forNon-Critical dimensions in mm
(Un-toleranced or rounded to nearest whole number.)

Length of Dimension "A" Zinc Aluminium Magnesium
Basic tolerance. Up to 25mm +/- 0.25 +/- 0.25 +/- 0.25
Additional tolerance for each additional 25mm.
Over 25 mm to 300 mm
+/- 0.04 +/- 0.05 +/- 0.05
Additional tolerance for each additional 25mm.
Over 300 mm
+/- 0.03 +/- 0.03 +/- 0.03

Parting line tolerances +

Parting line tolerances

Parting line tolerances, in addition to Linear dimensional tolerances, must provide for the movement of the die. The "Projected Area" is the area of the diecasting in square centimetres at the parting plane.

Additional Tolerance in Millimetres

Projected Area of Diecasting in cm2 Zinc Aluminium Magnesium
Up to 325 cm2 +/- 0.10 +/- 0.13 +/- 0.13
325 to 650 cm2 +/- 0.15 +/- 0.20 +/- 0.20
650 to 1,300 cm2 +/- 0.20 +/- 0.30 +/- 0.30
1,300 to 2,000 cm2 +/- 0.30 +/- 0.40 +/- 0.40

Moving Die Part Tolerances +

Parting line tolerances

Moving die part tolerances, in addition to Linear dimensional tolerances must be provided when a moving die part affects the dimension. The "Projected Area" is the area, in square centimetres of the portion of the diecasting affected by the moving die part.

Additional Tolerance in Millimetres

Projected Area of Diecasting in cm2 Zinc Aluminium Magnesium
Up to 65 cm2 +/- 0.10 +/- 0.13 +/- 0.13
65 to 130 cm2 +/- 0.15 +/- 0.20 +/- 0.20
130 to 325 cm2 +/- 0.20 +/- 0.30 +/- 0.30
325 cm2 and Upwards +/- 0.30 +/- 0.40 +/- 0.40

Tolerance for Flatness +

Parting line tolerances

The flatness should be measured with a feeler gauge from three widely separated points on a continuous plane surface of the diecasting. In the table below, "Dimension" means the maximum dimension (Diameter of a circular surface or diagonal of a rectangular surface.)

Flatness Tolerances. As Cast. (mm)

Dimension of diecasting. All Alloys
Basic Tolerance.
Up to 75 mm
0.20
Additional Tolerance.
For every 25 mm.
0.08

Porosity Standards +

Engineering Diecasting Specifications

These are acceptable porosity standards for machined surfaces. Acceptance to these standards is on a visual judgement basis without magnification.

Porosity Level 1

Pin Point Porosity, not larger than 0.25mm ( 0.01") in any direction is acceptable providing it is widely distributed. (Not grouped or connected.)

Random pits, not larger than 0.375mm ( 0.15") in any direction are allowable providing they are widely distributed. (Not grouped or connected.) They must be completely surrounded by dense parent metal and be a minimum of 6mm (0.25") apart.

Frequency of pits must be minimal.

Porosity Level 2

Pin Point Porosity, not larger than 0.375mm ( 0.015") in any direction is acceptable providing it is widely distributed. (Not grouped or connected.)

Random pits, not larger than 0.75mm ( 0.30") in any direction are allowable providing they are not grouped or connected.

Frequency of pits must not be excessive.

Porosity Level 3

Pits not larger than 1.25mm ( 0.05") in any direction are acceptable.

Exposed chain porosity must not exceed 3mm (1/8 ") in length.

Unless otherwise specified, exposed porosity on machined diecast parts will conform to this level.