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
+/- 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.
