School of Technology

TECH 13580 - Engineering Graphics I

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Sectioned views are recognized by having close thin black parallel lines called crosshatching or section lining, often at 45 degrees, within the view. The purpose of a sectioned view is to improve the reader's ability to visualize completely the object being drawn. The crosshatching indicates, in a conventional sense, the solid mass of the object in contrast to openings such as holes which are also called voids. Hidden lines in drawings not sectioned also serve the same purpose, but tend to become confusing when the drawing is complex, thus the value of sectioned views. Different crosshatch symbols also identify the type of material used to fabricate the part.

Crosshatching (Section Lining) - thin black lines usually (not always) at 45 degrees used to identify the object's mass, should not be parallel nor perpendicular to the object's outline, spaced apart by usually1/8" unless the object is very large to warrant greater spacing (pitch), drawn with center row of holes on Ames Lettering Guide or HATCH command in CAD. 

Cutting Plane Line - thick bold black line used to identify where cross-section is located, not drawn in same view sectioned, has arrowheads on its ends to indicate direction of view, two types of cutting plane lines exist. 

Hidden Lines within section views - usually not drawn, only drawn if absolutely necessary to identify a feature not otherwise visualized 

Visible Detail Behind Cutting Plane - draw visible features, not hidden features unless absolutely required for visualization as explained above 

Ribs in section - not drawn if parallel to plane because tends to imply greater mass than actual, drawn if rib runs perpendicular to plane, same true for spokes  isometric sketch of cement block with ribs sketch of section view of block

Conventional Practice - sectioning not a physical cut, a graphic cut - could be different such as ribs not sectioned and spokes not sectioned, also items usually not sectioned: ribs, spokes, bolts, pins, keys

Alternate Section Lining Technique - can be used to differentiate ribs from voids 

Alignment & Conventional Rotation - rotation of features of round object via compass to pretend as though located on center line to enhance clarity 

Intersections - when cut for section passes through a void, offset not shown unless large 

Full Section - cutting plane goes full way through view as though object cut in half  

Half Section - cutting plane goes half way in to view resulting as though 1/4 removed, ideal foe symmetric round objects, cutting plane has precedence over center line, only one arrowhead to indicate direction of view, interior and exterior lines terminate at center line, optional to draw hidden lines in unsectioned half, avoid hidden lines in sectioned half, ideal view to visualize both interior and exterior features in same view, helpful when dimensioning 

Offset Section - resembles full section except not a straight cut, cutting plane follows irregular route to cut through various selected features, cutting plane shows route but sectioned view does not reveal "bends" from change of direction 

Broken-Out Section - ideal to show a small area in section while leaving rest of view unsectioned, wavy line (short break symbol) drawn to separate broken-out section from unsectioned portion, usually no cutting plane required 

Revolved Section - portion of object spun 90 degrees "in place" to reveal shape, as though simultaneous front of object and side view in section

Removed Section - same concept as revolved sections except section not spun "in place" due to congestion, placed off view for clarity, requires identified cutting plane reading from left to right such as CUTTING PLANE A-A SECTION A-A, CUTTING PLANE B-B SECTION B-B, 

Auxiliary Section - an auxiliary view in section 

Partial Views in Section - to conserve space while still able to section 

Conventional Breaks - symbols for various shapes such as bar stock or tubing or various materials such as wood used to graphically discard large portions of stock to conserve space resulting in better scale of drawing