Introduction to Dimensioning © 2012 Project Lead The Way, Inc.Introduction to Engineering Design

Dimensions should reflect actual size of the object, not the scaled size. The dimension measured on the drawing is ¾ in., but the actual dimension of the part is 2 in. Therefore, show 2.00 on drawing.

Include overall dimension in the three principle directions – width, height, and depth. –Overall dimensions should be placed the greatest distance away from the object so that intermediate dimensions can nest closer to the object.

Include overall dimension in the three principle directions – width, height, and depth. –Overall dimensions should be placed the greatest distance away from the object so that intermediate dimensions can nest closer to the object.

Include all dimensions necessary to produce or inspect the part. Dimensions should be placed so that it is not necessary to calculate or scale a dimension. ? ? Incorrect

Include all dimensions necessary to produce or inspect the part.

Do not include unnecessary dimensions. Incorrect DUPLICATED Dimensions should NOT be duplicated or the same information given in two different ways.

Do not include unnecessary dimensions. Incorrect Do not include chain dimensions that add up to a given overall dimension. Provides the same information in two different ways.

Do not include unnecessary dimensions.

Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned. Incorrect

Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned.

A dimension should be attached to only one view; for example, extension lines should not connect two views. Incorrect

A dimension should be attached to only one view; for example, extension lines should not connect two views.

Whenever possible, locate dimensions between adjacent views. Incorrect

Whenever possible, locate dimensions between adjacent views.

Avoid dimensioning to hidden lines Incorrect

Avoid dimensioning to hidden lines. 0.75

Do not place dimensions on the object unless it is absolutely necessary. Incorrect

Do not place dimensions on the object unless it is absolutely necessary.

Do not cross a dimension line with another dimension line or with an extension line.

Avoid crossing dimension or extension lines with leader lines. Incorrect

Avoid crossing dimension or extension lines with leader lines. Ø 0.50 THRU

Leader lines point toward the center of the feature and should not occur horizontally or vertically.

Dimension numbers should be centered between arrowheads, except when using stacked dimensions, and then the numbers should be staggered. Incorrect

Dimension numbers should be centered between arrowheads, except when using stacked dimensions, and then the numbers should be staggered.

In general, a circle is dimensioned by its diameter and an arc by its radius.

Holes should be located and sized in the view that shows the feature as a circle. Incorrect

Holes should be located and sized in the view that shows the feature as a circle.

Holes are located by their centerlines, which may be extended and used as extension lines.

Notes 1.Dimensions should reflect actual measurement. –No scaling should apply 2.Include overall dimensions for length, width, and height –The longest dimension for each direction should be noted 3.Larger dimensions should be placed farther from the object. –Nest shorter dimensions inside longer ones 4.Include all dimensions necessary to produce or inspect the part –You should be able to pick up any drawing and produce it without having to look at the prototype.

Notes 5.Do not include unnecessary or duplicated dimensions. –Redundancies are not ‘good documenting,’ they add to confusion. 6.Dimension the view with the best contour. –Flat sides are rarely the best contour. 7.A dimension should be attached to only one view. –Look at your extension lines, they should only be drawn to one drawing. 8.Place dimensions between adjacent views. –Look at the two views that you are dimensioning. Pick the space between them to write the dimensions.

Notes 9.Avoid dimensioning to hidden lines. –Sometimes this can’t be avoided. 10.Do not place dimensions on/in the object. –All dimensions should be between or outside the drawings. 11.Do not cross a dimension line with another dimension or with an extension line. –same for leader lines – circles –Sometimes this can’t be avoided. 12.Leader lines are angled (30°, 45°, or 60°) and point toward the center of the feature. –Features are either holes are arcs, so there’s always a center.

Notes 13.Center dimension numbers between arrow heads. 14.Dimension circles by diameter, arcs by radius 15.Circles should be located by the center lines in the view that shows the feature as a circle.

References Bertoline, G. (2003). Technical graphics communication. (3 ed.). Boston, MA: McGraw-Hill. Giesecke, F. [et al.] (1991). Technical drawing. (9 ed.). New York, NY: Macmillan Pub. Co. Madsen, D., Folkestad, J., Schertz, K., Shumaker, T., Stark, C., & Turpin, J. (2002). Engineering drawing and design. (3 ed.). Albany, NY: Delmar Thomas Learning.