Unspecified Sheet metal tolerance followed in manufacturing industries

Unspecified Sheet metal tolerance followed in manufacturing industries

Unspecified tolerances for features

	Feature				Tolerance (mm)
	Edge	To	Hole	a	0.127
	Hole	to	Hole	b	0.127
	Hole	to	Self-Clinching Fastener (SFC)	c	0.254
	Edge	To	Edge	d	0.254
	Hole	to	Stud	e	0.254
	Bend	to	Hole	f	0.254
	SFC	to	Stud	g	0.381
	Bend	to	Stud	h	0.508
	Edge	to	Self-Clinching Fastener (SFC)	I	0.381
	Bend	to	Self-Clinching Fastener (SFC)	j	0.508
	Bend	to	Edge	k	0.254
	Edge	to	Stud	l	0.381
	Stud	to	Stud	m	0.381
	SFC	to	Self-Clinching Fastener (SFC)	n	0.381
	Bend	To	Bend	o	0.508

 

 

 

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Parallel and Compound Planes

The tolerance between features on two different planes is the sum of the tolerances between the first feature to the bend, the bend tolerances, and the tolerance between the bend and the second feature. An example is shown below.

+/- 0.015Hole (A) to Bend

+/- 0.020Bend To Bend

+/- 0.015Hole (B) to Bend
+/- 0.040 Tolerance between A and B

Surface Length

Surface Length (mm)	Flatness	Straightness of Cut
0 to 25	0.127 mm	0.41 mm / meter
25 to 102	5 μm / mm of length
above 102	0.51 mm + 4 μm / mm of length

 

 

Squareness

Squareness	SHEARED EDGE	FORMED EDGE
SHEARED EDGE	1.25 mm	1.67 mm
FORMED EDGE	1.67 mm	1.25 mm

 

 

Unspecified Edges and Burrs

chamfer or radius	0.5 mm or 10% material thickness
projections by piercing / blanking	0.15 mm  max

 

Bending

Right Angles

Angles that are not specified on the engineering drawing and appear to be 90 degrees are considered to be 90 degrees. The angular tolerance will be +/- 1degrees. The position of material (D) at the end of a bend will vary according to the length of the bend (L).

Acute Angles

The tolerance for acute angles is +/-1 degrees.

Obtuse Angles

The tolerance for obtuse angles is +/-1Ε

 

 

Bends and Material Grain

Whenever the bend configuration permits, a bend shall be made across the grain of the material, or at 45 degrees to the grain direction. minimum flange (bend length) the minimum recommended flange dimension should be at least 3.5 times the sum of the material thickness and the bend radius.

 

Distance of a Punched Hole from a Bend

 

The minimum inside dimension from a bend to the edge of a punched hole should be 1.5 times the sum of the material thickness and the bend radius. Punched holes located closer to a bend will have a tendency to distort and may lend to cracking of the material.

 

Material Thickness and Hole Size

 

Generally minimum hole size is limited to the thickness of the material.

 

Distance of a Punched Hole from Edge of Blank

 

To avoid distortion in sheet metal, holes must not be too close to an edge. For sheet metal 1/32 inch or less in thickness, all holes should be at least 1/16 inch from the nearest edge. The minimum distance from an edge for thicker material should be twice the thickness, but not less than 1/8 inch. The minimum distance between two punched holes should be at least twice the thickness of the material. If the holes are to have inserts, studs etc. pressed in the manufacturer’s recommendations for minimum distances should be observed.