Auxiliary Views

     Auxiliary views are used to show the true lengths parts of objects that do not have faces parallel to the normal three viewing planes. Auxiliary view are folded up from a normal view into the viewing plane. In the image shown above, the view at the center shows a front view of the object. The object curves upward at each end. The top view shows the the object as seen from the top, but the features at the ends are contorted due to the fact that they are viewed at an angle. the circles have become ellipses, and lines do not show the true length or angle of the surfaces of the part. The three views on the sides help show the true lengths and shapes of the angled features. Features that would be contorted in a normal view are dimensioned in an auxiliary view instead. The view to the far right is a secondary auxiliary view, because it is folded up from another auxiliary view. The auxiliary views in this drawing are partial auxiliary views, because they do not show the entire object. Sometimes, a short break line is used to show where the object would continue if it were shown.
     Without Auxiliary views, tedious trigonometric calculations would be necessary to find the actual lengths of features at angles, and dimensions might have to be drawn to hidden lines more often, and features would not be dimensioned in their primary view.

Sectional Views: Is the glass half empty, half full, or half sectioned?

     In the sectioning unit, I learned about full and half sections,  and revolved and removed sections.
These methods of sectioning bring clarity to drawing by giving a view of the inside of an object without the use of Hidden lines. Hidden lines can become confusing in complex drawing. Sectional views are an intuitive way of avoiding this confusion.
     Half and full sections essentially cut way the front quarter or the front half of an object so that the features of the back half of the object can be seen directly. A cutting plane line indicates where an object has been cut, and which part of the object has been removed from the sectional view. The section line appears in a different view than the sectional view. In the sectional view, section lines are drawn at a 45 degree angle to the surfaces of the drawing wherever the part is cut by the section. These lines are about 1/16" apart. The differentiate surfaces that are flush with the cutting plane from surfaces that are recessed. In full sections, an entire view will be cut by the cutting plane. In half sections, only half of the view is cut by the section view. In the drawing above, The view on the right is in half section.

     Revolved and removed sections are sectional views of specific regions of an object. A revolved section appears inside a normally drawn object. Part of the object is broken away, and the sectional view shows what the object would look like if it were cut away and rotated ninety degrees. Section lines are used on the foremost surfaces. Usually, features of the object behind the revolved section are ignored in the section. In a removed section, a section of a part of an object is shown in a view on its own.  Notes are used to show where the cutting plane is and which view shows the section made by that cutting plane.
     These types of sectional views, as well as other types are used often to make parts easier to understand, and to show the true shape of the inside of a part without hidden lines.