Flatness Tolerance For Sheet Metal

The flatness control c defines how much a surface on a real part may vary from the ideal flat plane.

Flatness tolerance for sheet metal.

As per design requirements and manufacturing capability tolerance class is defined. Since rolled alloys also levels this product we work to the mill tolerances. For material 10 or less in length variation should not exceed amount shown in table. For sheet metal parts iso 27 68 mk is used.

Tolerances of 010 should be considered minimum. Flatness tolerances listed are of roller leveled sheets or plates with no or minimum margins. And for machined components iso 27 68 fh can be used. Squareness tolerances flat sheet and plate.

Plates can be out of flat for a number of reasons. Mm 48 1 219 in. Parts may be measured in either unrestrained or restrained conditions. Sheet metal tolerances should not be tighter than necessary to make the part functional.

Linear tolerances should be held as loose as possible. This not only control the rock but also the allowable mechanical stress which deform the shape of the sheet metal like in case of parts that will be welded thermal stress bolted bending due to too much torque or screwed. Flatness tolerance is always less than the dimensional tolerance associated with it. Up thru 3 over 3 allowable difference in length of diagonals inches.

Tight tolerances raise the cost of manufacturing significantly. Flatness tolerance is the permissible distance between two parallel planes within which all irregularities of a given surface must lie. Sheet metal is often controlled with flatness tolerance. The flatness tolerance references two parallel planes parallel to the surface that it is called out on that define a zone where the entire reference surface must lie.

For material longer than 10 the variation in flatness for any 10 feet of length should not exceed the amount shown. Note any feature requirement comes with price tag on it. Specified width ft. The flatness tolerance zone is the volume between two parallel planes.

In general sheets 60 wide and under are to be no more than out of flat when laid on a flat surface. In the above example m and k has defined the tolerance class. The distance between the parallel planes is the stated flatness control tolerance value. Maximum difference between aa and bb up thru 12 over 12 3 32 x width ft 2 9 64 x width ft 2 5 64 x width ft 2 7 64 x width ft 2.

General tolerance iso 2768 does not specify where to use these tolerances. Practical tolerances vary according to the design requirements. Two sets of parallel planes where the entire referenced surface must lie.