FLATNESS

The surfaces for flatness can be measured by supporting the surface in question on three widely separated points to establish the basic plane. A flatness tolerance is the total deviation permitted from that plane. It consists of the distance between two parallel planes within which the entire surface so toleranced must lie.

0 thru 6 inches 0.030
Ea. addl. in. thru 24 in. 0.003 in./in.
For castings over 24 in. consult foundry.

Many foundries can achieve tolerances better than above, but may require additional tooling and gauges. Checking for flatness will be performed only on those surfaces specified on the blueprint.

Exceptions may be required on certain configurations and alloys. Consult the foundry.