Section 57 of 103
56. Tolerance, Clearance and Allowance
Stable section ID: S05-CON-015-SECTION-57 · 14 content blocks
A Tolerance is the permitted variation from a specified nominal value, geometry, position, orientation, property, or performance target.
A Clearance is the available space between adjacent entities or within an access region. Clearance may support assembly, movement, ventilation, thermal expansion, inspection, maintenance, tool access, or safe separation.
An Allowance is an intentional dimensional or performance difference introduced between related entities to achieve a required fit, preload, movement, transition, or manufacturing condition.
Tolerances may be geometric, dimensional, manufacturing, assembly-related, inspection-related, operational, environmental, digital, or lifecycle-based.
Tolerance requirements shall consider:
cumulative tolerance stack-up;
material and manufacturing variability;
temperature, moisture, creep, wear, and deformation;
installation and measurement capability;
human and robotic assembly;
inspection uncertainty;
replacement compatibility.
A tolerance shall not be selected solely according to manufacturing convenience. It shall support the required function throughout the relevant lifecycle.
Clearance shall not be interpreted as misalignment, and allowance shall not be treated as uncontrolled variation. Unspecified tolerance shall not imply unlimited precision or unrestricted deviation.