Sometimes it is necessary to cut a part or assembly to reveal geometry or fits on the inside of a part or assembly. A Section or cross section is a view generated from a part or assembly on a cutting plane or multiple cutting planes that reveals the outlines on the inside or assembly fits. Sections normally comprise of two parts, firstly the Section Cut indicator with identification. This indicator will then generate a Section view.
Section Cut indicators
Section cut indicators identifies the plane where, how and on which planes the section cut is made. The line that indicates the plane where the cut is made is called the section line. Arrows indicate the direction of view. This identifies the orientation of the view that is created also.
A Full section view is where the entire part or assembly is cut on a single plane. The generated section view that is created may form part of the same view as the reference view, permitted the correct projection method (first or third angled projection) is used. Should the draftsman choose not to use this method, a separate view will be created and a identification heading needs to be assigned to it.
The half section view may be used where a part or assembly is symmetrical about the centerline of the part or assembly. This will save space on the drawing with over population of reference and section views. It is important to remember that when using half sections, certain rules apply to the visibility of the center line. If the hatching generated by the cut touches the center line, a solid line needs to be drawn through the whole part or assembly. If the hatching does not touch the center line, no solid line needs to be indicated on the center cutting plane.
A Partial section is used when only a certain portion of a part or assembly is cut in order to show important detail or geometry. The whole part or assembly is not sectioned as that may minimize the other information show. A break line is used to show the cutting plane, although the cut line may not necessarily be on a specific plane.
A revolved section is a section that is made at a certain point in a part and revolved 90° to show the cross section of the part. The part can be broken to show the revolved section or the revolved section can be superimposed on the part itself. This is helpful to show the cross section at different intervals of a part where the part has complex contours.
A removed section works on the same principle as the revolved section. The section however is not placed on the part but rather projected on the cutting plane outside the outlines of the part.
Thin Components in sections
When sectioning thin components, space around the components should be created as the lines and hatching may display as one solid black line. An alternative is to rather use a enlarged partial section to show the detail that is of interest.
Successive sections are shown in line to identify certain features on a part or assembly. If space is a constraint on the drawing, separate section views should rather be used
Exceptions to Sections
The following elements should not be sectioned when the cutting plane passes through them. Ribs, shafts, bolts, nuts, rivets, rods, keys, pins and similar components.