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Flatness Tolerances

The flatness of a casting can be measured by supporting the surface in question on three widely separated points to establish a datum and measuring the deviation from that plane by the use of feeler gauges.

The flatness tolerance is the total deviation permitted from the datum and consists of the distance between two parallel planes within which the entire surface so tolerated must lie.

Pressure Diecasting
Maximum Dimension
Up to 75mm	within 0.2
for each additional 25mm	add 0.075

Gravity Diecasting
Maximum Dimension
Up to 150mm	within 0.5
for each additional 25mm	add 0.075

Sand Casting
Maximum Dimension
Up to 150mm	within 0.75
for each additional 25mm	add 0.075

The values shown represent production practice at the most economical level.  Greater accuracy involving extra work or care in production should be specified only when and where necessary.