# Geometrical Tolerancing Geometrical Tolerancing
Types of tolerancing
Symbol
Definition
Form tolerance
Straightness tolerance Tolerance for deviation of straight object from the geometric straightness
Flatness tolerance Tolerance for deviation of flat object from the geometric flatness
Roundness tolerance Tolerance for deviation of round object from the geometric roundness
Cylindricity tolerance Tolerance for deviation of cylindrical object from the geometric cylindricity
Profile tolerance for line Tolerance of deviation of a line profile from the geometrical profile defined by the theoretically accurate dimensions
Profile tolerance for plane Tolerance of deviation of a plane profile from the geometrical profile defined by the theoretically accurate dimensions.
Orientation tolerance
Parallelism tolerance Tolerance for deviation of straight line object or plane object that are assumed to be parallel to the geometrical straight line or geometrical plane that are parallel to datum straight line or datum plane.
Squareness tolerance Tolerance for deviation of straight line object or plane object that are assumed to be right angle to the geometrical straight line or geometrical plane that are right angle to datum straight line or datum plane.
Angularity tolerance Tolerance for deviation of straight line object or plane object that are assumed to have an accurate angle to the geometrical straight line or geometrical plane that have the accurate angle to datum straight line or datum plane.
Position tolerance
Positional tolerance Tolerance for the deviation of a point, straight line object or plane object from the accurate position defined in relation to datum or other geometric feature.
Coaxiality tolerance or concentricity tolerance Coaxiality tolerance is tolerance of the deviation for the axis line that is assumed to be on the same straight line with datum axis line, from the datum axis line. On the other hand, concentricity tolerance is tolerance for the position deviation from the center of datum circle to the center of other circular geometric feature.
Symmetry tolerance Tolerance for the deviation of actual body that is assumed to be symmetrical to each other against the datum axis straight line or datum central plane, from the symmetrical position.
Run-out tolerance When a rotating body whose axis is datum axis straight line rotates around the datum axis straight line, the tolerance represents the permissible displacement of its surface from the specified position or at an arbitrary position along the specified direction.
Total run-out tolerance When a rotating body whose axis is datum axis straight line rotates around the datum axis straight line, the tolerance represents the permissible displacement of its surface along the specified direction.

Property symbol Definition of tolerance zone
Example and explanation of instruction method
Straightness tolerance  When adding the symbol φ
before the tolerance value, the
geometric tolerance zone is
restricted by the cylinder
whose diameter is t. The actual (reproduced) shaft
line of cylinder to which
tolerance is applied must be
within a cylindrical tolerance
zone of 0.08 in diameter.
Flatness tolerance  The tolerance zone is
restricted by parallel two
planes apart by distance t. The actual (reproduced)
surface must be within the
parallel two planes apart by
distance 0.08.
Roundness tolerance  In the symmetric cross section,
the tolerance zone is restricted
by two circles with the
common axis. In an arbitrary cross section of
a cylinder or a circular cone,
the actual (or reproduced) line
be between the two circles on
the common plane with the
common axis that are 0.03
Cylindricity tolerance  The tolerance zone is
restricted by two cylinders
with the common axis apart by
distance t. The actual (reproduced)
cylindrical surface must be
within the two cylinders with
the common axis apart by
Profile tolerance of a line: Profile tolerance of a line that is not related to datum (ISO 1660)  Tolerance zone is restricted by
two envelope curves of each
circle with diameter t, and the
centers of these circles are
positioned on a line that has
the theoretically accurate
geometrical configuration. In each cross sections that are
parallel to project plane along
the specified direction, the
actual (or reproduced) profile
line must be between the two
envelope lines of circles which
have the diameter 0.04 and
whose centers are positioned
on an idealistic geometrical line.
Profile tolerance of plane: Profile tolerance of a plane that is not related to datum (ISO 1660)  Tolerance zone is restricted by
two envelope curves of each
sphere with diameter t, and
the centers of these spheres
are positioned on a line that
has the theoretically accurate
geometrical configuration. The actual (or reproduced)
surface must be between the
enveloping surfaces of each
spheres whose diameter is 0.02
and whose centers are
positioned on a theoretically
accurate geometrical surface.

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