Class 10_2

• Practice dimensioning drawings

Questions about DP?

Lines

Line types (e.g., part, hidden, center)Line values (e.g., thick, intermediate,

construction)

It is important to use the proper line type and line value in your drawings. It communicates important information and makes drawings easier to understand.

Section views

• Section views “cut-away” part of the object so that internal details can be revealed.

Section views

• Section view are also used to show assembly details

Section view conventions

• Cut surface is filled with a “hatch”• Part lines behind cutting plane are shown• Hidden lines behind cutting plane are

generally not shown• Section view can take the place of one

orthogonal view or can be auxiliary views

Section view types

• Many section view types. A few examples…

Dimensioning

• Dimensioning of technical drawing is, of course, crucial

• There are well established conventions (rules) for proper dimensioning

• Handout

Reading of the rules…

Each feature of an object is dimensioned once, and only once.

Dimension should be selected to suit the function of the object.

Dimensions should be attached to the most descriptive view of the feature being dimensioned.

Dimensions should not specify the manufacturing method.

Avoid dimensioning to hidden lines.

Avoid placing dimension inside the object.

Dimensions should be aligned and grouped to promote uniform appearance.

Dimension lines should be unbroken except for the number between arrowheads.

There should be a visible gap between the object and the extension line.Extension lines should extend past the last dimension line.

Leader lines used to dimension circles or arcs should be radial.

Dimensions should be oriented to be read from the bottom of the drawing.

Positive cylinders should be dimensioned in the longitudinal view.

Diameters are dimensioned with the numerical value preceded by the diameter symbol (f).

Radii are dimensioned with the numerical value preceded by the radius symbol (R).

Dimension to the center of cylinders, holes, and arcs.

Dimensioning practice

• Draw a 3-view orthographic projection• Dimension fully• You can guess the dimensions• Take the hole diameter as 1 inch• Remember to leave room for dimensions

That’s it for today

Have a safe and relaxing break!