This Weeks Topic:

Auxiliary Views & Sections

Auxiliary Views

Introduction:

Objects are designed to have sloping of inclined surfaces that do not appear true size in principal views. A plane of this type is not parallel to a principal projection plane, (horizontal, frontal, or profile) and is therefore a non-principal plane. Its true shape must be projected onto a plane that is parallel to it. This view is called an auxiliary view.

Folding Line Method:

The inclined surface of the part in Figure 8.1 does not appear true size in the top view because it is not parallel to the top plane. However the inclined surface will appear true size in an auxiliary view projected perpendicularly from its edge view in the front view.

The relationship between an auxiliary view and the view it was projected from is the same as that between any two adjacent orthographic views.

The three principal orthographic planes are frontal, horizontal, and profile. An auxiliary view is projected from a principal orthographic view and a primary auxiliary plane is perpendicular to one of the principal planes and oblique to other two.

It is important that reference lines be labeled as shown in Figure 8.10 with the numeral 1 place on the auxiliary side and the letter H, F, of P on the principal plane side.

A surface must appear as an edge in a principal view before it can be found true size in an auxiliary view.

An auxiliary view must be projected perpendicularly from the edge view of the surface to be found true size.

Construction lines and projectors should be drawn as light lines, just dark enough to be seen.

Always transfer dimensions from principal views perpendicularly from the fold lines to auxiliary views. Use your compass to transfer these dimensions to the auxiliary view.

Partial views:

Auxiliary views are used as supplementary views to clarify features that are difficult to depict with principal views alone. Consequently, portions of principal views and auxiliary views may be omitted, provided that the partial views adequately describe the part.(See Figures 8.25 & 8.26)

Sections

Introduction:

Correctly drawn orthographic views that show all hidden lines nay not clearly describe an objects internal details. This shortcoming can be overcome by imagining that part of the object has been cut away and shown in a cross-sectional view, called a section.

Cutting Plane:

Figure 9.1 shows pictorially a section created by passing an imaginary plane through the object to reveal its internal features. Think of the cutting plane as a knife cutting through the object.

In the areas where the cutting plane passes through solid material section or hatching lines are drawn to represent the portions of material which have been cut away.

Hatching Lines:

Figure 9.4 show hatching symbols used to distinguish between different materials in sections. The cast iron symbol is commonly used to represent any material.

When hatching a sectioned part the lines should be evenly spaced, and not too close together, nor too far apart (See Figure 9.5). Also the lines should neither be perpendicular, nor parallel to the outline being hatched.(See Figure 9.7)

When sectioning very thin parts by completely blacking them in, since hatching them would essentially do the same thing. When sectioning assemblies hatching lines are drawn at varying angles to distinguish parts from one another.(See Figure 9.6 & 9.8)

Hatching Conventions:

Hardware such as nuts, bolts, washers, etc. do not require hatching even though the cutting plane passes through them. Since these parts have no internal features sections would have no value.(See Figure 9.12)

Figures 9.13-9.15 show how ribs and webs are dealt with in section views. The rule of thumb here is that if a rib is an external feature (Figure 9.13a) the rib is not hatched. If the rib or web in an internal feature (confined by other features of the part) it is hatched.

When representing an internal rib or web it is sometimes hatched the same way as the rest of the part (Figure 9.13b) and other times with an alternate hatching pattern. (Figure 9.14c)

Partial Views:

Sometimes it is only necessary to show a section of a small part to clarify an internal feature of a part. This is when a broken section is used. A broken section is where the area which is obscuring the feature which needs to be defined is "broken away" to show the feature beneath.(See Figure 9.21 & 9.22)

• An auxiliary view is nothing more than an orthographic view of an inclined plane projected from one of the six principal views
• A section is a cut away view used to show interior features of a part