Sectional views

1. Sectional views

2. Full Section • Imagine the object cut through by the cutting plane. Think of the two halves pulled apart and a view looking on to the cut half.

3. Full section in drawing • Full sections show the object cut in half • Cutting plane line can be left out because it is understood to be through centre • Can replace a standard view

4. Cutting plane line • The cutting plane line is a thick dark line at ends which uses one of the special patterns shown above. • The cutting plane line can be left out when it is obvious where it must lie from the appearance of the section itself.

5. Cross Hatch Symbols • Typical patterns for hatching used to denote different materials: Water, Liquids Cast Iron (General Use) Wood; Cross Grain With Grain

6. Crosshatching Section Views • Crosshatching, is a repeating graphic pattern which is applied throughout all areas of the part that would be in contact with the cutting plane. Thus, the hole is not crosshatched. • The recommended angle for the standard crosshatch pattern is 45, 30, or 60 degrees with horizontal. Similarly, crosshatch lines should be neither parallel nor perpendicular to the outline of the feature in section—if avoidable (see the examples below). Good Practice Poor Practice Poor Practice

7. Dimension Values & Hatching • Sectional views are often used to show interior features clearly for dimensioning. If dimension values or extension lines cross hatched areas, you should break the hatching behind the dimension. The best practice is to place dimensions outside the object outline

8. Half section(Typical for symmetrical components)

9. Local or Part section Bolt F10 Socket F12

10. Aligned sections

11. Revolved section and Interposed section • Revolved section shows the shape of the cross-section in the actual view of the object • Interposed section

12. Removed section • Sections are removed from actual view of the object • Can be placed anywhere in the drawing but well labelled Alternatively if you wish to rotate the section it shall be indicated: C-C Rotated 75 Clockwise

13. Conventions: • Fastening elements: Where the cutting plane through an assembly contains the centreline of fastening elements such as bolts, pins. Rivets, key, washers, nuts, screws, or other elements such as shafts, rods, ball and roller bearings, and similar shapes which in themselves do not require sectioning, the elements shall not be sectioned but shall be shown in full outline [AS 1100.101-1992]

14. Relatively thin elements: where the cutting plane through an object passes longitudinally through a relatively thin element of the object such as a web, rib, lug or spoke, the outline of the feature may be drawn without hatching in order to avoid a false impression of solidity [AS 1100.101-1992]

15. [AS 1100.101-1992] • Holes: In a sectional view of an element, holes may be shown, even if not in the cutting plane. Holes in circular elements should be shown at the true pitch from the centre rather than at the projected distance • Breaks: Break lines as illustrated may be used to shorten a view of elongated objects.

16. Summary: • Sections are used to show interior details clearly • A cutting-plane line shows where object was cut to obtain the section view. • Cross hatching in the section view shows the solid surface of the object which were cut through to produce the section. • Section views may replace standard view • Conventional practices, such as not showing hatching on ribs and webs, help make sections easier to interpret correctly. • Pins, bolts, washers, etc. ,that does not required sectioning shall not be sectioned in sectional views