CGT 110 – Technical Graphics Communication

CGT 110 – Technical Graphics Communication

Week 6:

Section Views


Week 6: Section Views

Here’s what we talked about last time…..



We can also use the glass box technique to add an additional Picture Plane (PP) to project inclined surfaces to.

By doing so, we can show the slanted surface’s true shape and size.

NOTE:

The new glass plane is parallel to the surface it describes just like the other glass projection planes.



Here’s how to lay out an auxiliary view:

Step 1:

Make a new PP line labeled “1” that is parallel to Line AD in the FRONT view.

This PP may be placed any distance from the object you wish.



Step 2:

Add the other PP lines as shown so they will connect to PP 1.

It is always a good idea to label the PPs as shown.



Step 3:

Project the end points of Line AD at a 90 degree angle from the front view.



Step 4:

Transfer the distance from PP to point C in the TOP view…

…to its new position from PP 1 in the auxiliary view.



Step 5:

Connect the new point C with the projected line to find point B.

Do the same thing for points A and D.



Step 6:

Snap your lines in the auxiliary view to create its final form.

NOTE: You do not need to label all points on your drawing.



Let’s now take a look at how we can show hidden information using section views…..



Section views are used to expose hidden features. When we “open up” an object and view interior features, we see them not as hidden lines, but as object lines.



The “Cutting Plane” is a flat surface that identifies:

1. Which section of the object is to be shown, and

2. The path of the imaginary cut through the object



Figure A illustrates the proper technique that should be used to show a section view

A. A correctly drawn section view which uses both object and section lines.

B. An improperly drawn section view where the hidden lines have not been replaced with object lines.

C. A normal multiview projection of the part.



The Cutting Plane Line:

1. Is used to show where the object is being cut

2. Shows the Line of Sight (LOS) so a proper section view can be drawn.

3. Replaces the need to draw an entire cut-ting plane

Why is the example shown on the right incorrect??



Cutting Plane lines are the heaviest of all lines used in drafting. They are drawn much like center lines, but have 2 short dashes in them. The arrows on their end show the line of sight.



Every material has a “hatch line “ pattern.

Cast Iron can be used as the generic hatch line for any material. If you use this symbol, a “general note” should be added to the plate to identify the proper material used in the part.



Please review images 14.20 through 14.23 to review how hatch lines are drawn in diverse applications. Here are some general rules:

1. Hatch lines should never be drawn parallel to the edge of an object. Always use a slightly different angle so it makes the object easier to read.

2. If you have large interior areas to hatch, using short hatch lines around the perimeter is an acceptable practice.

3. If there needs to be notes or dimensions placed inside a hatched area, leave “white space” in the center of the hatch area to add these items.



The full section is the most common type of section view used.

It is known as a “FULL” section because the cutting plane passes through the full length of the object.



“Half” sections show the interior of an object where the cutting plane has penetrated only half way through the object.

NOTE:

The cutting plane line may only have one arrow on it.



“Broken” sections have no cutting plane line and are used to show a small, localized area of the object.



“Revolved” section views are used to show diverse shapes that may appear in a part.

Here we see that the section lies on the area it describes and may be placed on top of object lines, or be shown as part of a broken out section to assist whoever is reading the plate.



“Removed” sections allow the sectional view to be placed in another area of the plate so as not to crowd other views. All removed views are labeled on their cutting plane and the view.



“Offset” sections use a cutting plane that jogs to pick up valuable features of the part.



Sectioned assemblies are used to show relationships between parts.

NOTE: The hatching lines alternate direction on parts that are adjacent to one another.



Drawing styles may sometimes be combined with one another. Here we see an auxiliary and section view combined.



Examples of sectioning conventions...














Week 7:

Dimensioning

Documents

CGT 110 – Technical Graphics Communication