Sheet Metal Design, Mechanical Tolerances and Overview

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Related Resources:

• Sheet Metal Gauge Size Chart
• Bend Allowance Equation and Calculator
• Force to Shear or Pierce Sheet Metal Equation

Tolerances: Sheet metal tolerances should not be tighter than necessary to make the part functional. Tight tolerances raise the cost of manufacturing significantly. Practical tolerances vary according to the design requirements. Tolerances of +/- .010 should be considered minimum. Linear tolerances should be held as loose as possible. Recommend +/- .020 for general, and tolerance functional areas as needed.

Flatness: Flatness specifications are applied with perfect form not required at maximum material condition. If there is a rule of thumb, a flatness tolerance of .005" per inch is the best that can be achieved without secondary individual checking and straightening. In general the primary datum should have some type of form specified. Defining the primary datum by datum targets in a retrained condition is preferred.

Minimum Bend Radii: The minimum bend radii data contained within the given charts are measured to the inside of the bend. The bend radii listed are standard minimum for manufacturing for aerospace and space applications. Commercial sheet metal radius are created with less concern for stresses created during forming and radii can approach zero (sharp internal corner) for many thin sheet metal gages. Grain Direction A "grain" is formed in metal in the direction in which the sheet is rolled at the mill. Be careful not to confuse this with surface finishes produced by grinding of other finishing operations. Grain direction is usually specified on stainless steel and other hard materials when it is necessary to maintain minimum bend radius or to control spring back on parts with large radius forms. The grain can be seen by viewing off the shelf sheet and noting the direction of visible lines running end to end.

General: Concurrent design processes almost always reduces iterations between design and manufacturing. Submit preliminary designs to manufacturing for recommendations and review. Manufacturing comments almost always results in less expensive, more manufacturability, better parts and ultimately designs. ALUMINUM (BARE & CLAD) Minimum Bend Radii

Note: Bend radius of zero is achievable for .012 - .050 material thickness. Commercial applications

Aluminum Sheet Metal Size Table Chart

MATERIAL	SHEET THICKNESS
--	.012	.016	.020	.025	.032	.040	.050	.063	.071	.080	.090	.100	.125	.160	.190
2024-0 & W	.06	.06	.06	.06	.06	.06	.09	.09	.12	.12	.16	.19	.22	.31	.36
2024-T3	.06	.06	.06	.09	.09	.12	.16	.22	.25	.31	.38	.44	.62	.75	1.00
2024-T36	.06	.09	.09	.09	.12	.16	.19	.25	.31	.38	.44	.50	.75	1.00	1.25
3003-0	.06	.06	.06	.06	.06	.06	.06	.06	.09	.09	.09	.12	.12	.16	.19
3003-H14	.06	.06	.06	.06	.06	.09	.09	.12	.12	.16	.19	.22	.31	.38	.44
5052-0	.06	.06	.06	.06	.06	.06	.06	.09	.09	.09	.12	.12	.16	.19	.22
6061-0 & W	.06	.06	.06	.06	.06	.06	.06	.09	.09	.09	.12	.12	.16	.19	.22
6061-T4 & T6	.06	.06	.06	.06	.06	.06	.09	.09	.12	.12	.16	.19	.22	.31	.38
7075-0 & W	.06	.06	.06	.06	.09	.09	.12	.16	.19	.22	.25	.31	.38	.50	.62
7075-T6	.06	.09	.12	.12	.16	.22	.25	.31	.41	.44	.50	.69	.87	1.00	1.25
7178-0 & W	.06	.06	.06	.06	.09	.09	.12	.19	.22	.25	.31	.38	.50	.75	-
7178-T6	.06	.09	.16	.19	.22	.31	.38	.50	.56	.62	.62	.75	1.00	1.25	-