Tolerances For Formed Sheet Metal

A tolerance or set of tolerances is made to give the manufacturer of a metal product some measurement allowance in the production process.

Tolerances for formed sheet metal.

Tolerances are needed because metal forming processes have unpreventable sources of variation. General tolerance iso 2768 does not specify where to use these tolerances. Tolerances of 010 should be considered minimum. Critical dimensions sheet metal forming outside dimension should be used unless the inside dimension is critical.

The tolerances in the table and attachments reflect current manufacturing practices and commercial standards and are not representative of the manufacturer s standard gauge which has no inherent tolerances. Tight tolerances raise the cost of manufacturing significantly. As per design requirements and manufacturing capability tolerance class is defined. A tolerance is a range of acceptable measurements outside of the nominal dimension.

Uncontrolled dimensions contain two different categories of tolerances. Practical tolerances vary according to the design requirements. Sheet metal guage tolerances during the rolling process the rollers bow slightly which results in the sheets being thinner on the edges. Tolerances and allowances are exact and there s no need to add any feature or change the design to accommodate the shop floor or real world material behavior.

1 all manufacturing tolerances used up to that point such as laser cutting tolerances welding tolerances and more 2 all bend tolerances for the entire part added together we call this an uncontrolled dimensions because there are additional tolerances to consider. And for machined components iso 2768 fh can be used. A literature review of sheet metal forming errors as well as geometrical dimen sions and tolerances gd t shows that the theoretical means for the allocation of process tolerances with respect to. This also means that tolerances in the title block of a drawing may be unnecessarily restrictive for certain dimensions and angles while very appropriate for others.

The resulting bend angle variation and sometimes the required adjustment to the flat layout contributes to the reason that machined parts typical tolerance of 0 002 in can routinely have tighter tolerances than precision sheet metal parts typical tolerance of 0 010 in. Tolerances sheet metal tolerances should not be tighter than necessary to make the part functional.