Dimensioning, Continued
Dimension
techniques
All dimension lines and arrowheads must lie in the planes of the object to
which they apply. Align dimensions and notes shown with leaders to the
bottom of the drawing. Notes without leaders should also align with the
bottom of the drawing.
Use single-stroke gothic letters for dimensions and
lettering on drawings.
For clear dimensions, follow these general rules:
Show sufficient dimensions to define size, shape, and position of each
feature.
Place dimensions on the view that most clearly represents the form of the
geometric component of the part.
Express each dimension so that it can be interpreted in only one way.
Place dimensions outside of the object outline except when it helps to
clarify.
Never use centerlines, object lines, or extension lines as dimension lines.
Select and arrange dimensions to minimize the accumulation of tolerances
between related features.
Do not double dimension. Do not locate a feature by more than one
tolerance dimension in any one direction.
Never cross dimension, extension, and leader lines unless absolutely
necessary.
Never break a dimension line except for inserting dimensions.
Never run an extension or leader line through a dimension line or break it
except where it passes through or is adjacent to arrowheads.
Avoid dimensioning to hidden lines.
Express angular dimensions in degrees (°), in minutes (´) and seconds (),
or in decimal parts of a degree.
Do not use zeros before the decimal point for values less than 1 inch.
Enclose dimensions in. parentheses or mark “REF” when it is (1) repeated
on the same drawing, (2) specified on subordinate documents, (3) an
accumulation of other dimensions, or (4) shown for information only.
Do not use the word “TYPICAL” or the abbreviation “TYP.” Instead,
indicate (in parentheses) the number of places to which the dimension
applies (2 PLS).
Continued on next page
3-29
