Engineering communication: How are mechanical assemblies for lifting devices represented in engineering drawings, including assembly views, sectional views and standard symbols?
Read and produce engineering drawings of mechanical assemblies in third-angle orthogonal projection and isometric pictorial views, apply AS1100 sectional views and standard symbols for fasteners and welds, and prepare an assembly drawing with a parts list
A focused answer to the HSC Engineering Studies Lifting Devices dot point on assembly drawing. Detail versus assembly drawings, sectional views, fastener and weld symbols, isometric pictorial views, parts lists and balloon callouts, and worked HSC-style past exam questions.
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What this dot point is asking
NESA wants you to read and produce engineering drawings of mechanical assemblies, including detail drawings of single parts and assembly drawings showing multiple parts together. You must apply AS1100 conventions for sectional views, standard symbols (fasteners, welds, surface texture, geometric tolerance), and you must be able to construct a parts list keyed to balloon callouts.
The answer
Detail drawing versus assembly drawing
A detail drawing shows a single component, fully dimensioned, with material, finish and tolerance information. Each manufactured part has one detail drawing.
An assembly drawing shows multiple components together as built, with overall dimensions, weight, balloon callouts identifying each part, and a parts list (bill of materials). Internal dimensions of individual parts do not appear on the assembly drawing; they are on the detail drawings.
Sectional views
When internal features cannot be clearly shown with hidden lines, AS1100 allows section views.
- Full section
- The cutting plane passes completely through the part. Used for the majority of single-part section views.
- Half section
- The cut goes through only half the part, along a plane of symmetry. The other half remains an exterior view. Saves space on symmetrical parts.
- Offset section
- The cutting plane bends to pass through several features that are not on a single straight line. The bends are not shown on the section view.
Broken-out section (local). A small region is cut and hatched to reveal a single internal feature without sectioning the whole part.
Revolved section. A cross-section taken perpendicular to a long member (a shaft, an arm) is rotated into the plane of the view and drawn in place.
Standard symbols under AS1100
| Symbol | Use |
|---|---|
| Threaded fastener | External and internal threads with simplified representation |
| Weld symbol | Arrow, reference line, weld type (fillet, butt, square), size, length |
| Surface texture | V-symbol with surface roughness Ra in micrometres |
| Geometric tolerance | Boxed symbol indicating straightness, flatness, perpendicularity, runout, etc. |
| Centre of gravity | Crossed centre marker |
| Material indication | Hatching pattern in section views |
Isometric pictorial views
For three-dimensional clarity, an isometric view is drawn with three axes at 120 degrees apart in the plane of the drawing. AS1100 specifies the isometric grid and allows isometric drawings as supplementary pictorial views, never as the sole orthogonal projection. Lifting-device assemblies are often shown in isometric on the cover sheet to give the reader spatial context.
Parts list and balloon callouts
Each part on the assembly drawing is labelled with a balloon (a numbered circle on a thin leader line) pointing to the part. The parts list (bill of materials) is at the bottom right of the sheet, above the title block:
| Item | Qty | Description | Material | Drawing number |
|---|---|---|---|---|
| 1 | 1 | Hook body | AS3678 grade 350 | 100-01-01 |
| 2 | 1 | Trunnion pin | EN24 quenched and tempered | 100-01-02 |
| 3 | 2 | Side plate | AS3678 grade 350 | 100-01-03 |
| 4 | 4 | M20 hex bolt grade 8.8 | (purchased) | AS1110 |
Assembly drawings in lifting
A tower crane drawing package typically includes assemblies for the mast section, the slewing platform, the operator cab, the counter jib with ballast, the working jib with hoist trolley, and the hook block. Each assembly references detail drawings of every fabricated part. Field installation drawings show the mast climb sequence and torque values for the assembly bolts.
Past exam questions, worked
Real questions from past NESA papers on this dot point, with our answer explainer.
2021 HSC style5 marksA mechanical assembly drawing of a lifting hook and shackle uses a half-section view. Explain when a half-section is preferred over a full section, and describe how the section is identified on the drawing in accordance with AS1100. Identify two AS1100 standard symbols you would expect to see on an assembly drawing of a lifting device.Show worked answer →
Half-section. A half-section shows the object cut through one half along a plane of symmetry, with the other half drawn as a normal exterior view. It is preferred when the part is symmetrical about the section plane. Drawing only half saves space and makes the relationship between external geometry and internal features (bores, threaded sections, keyways) immediately visible without losing information.
A full section, by contrast, cuts the entire part along the plane and is used when the part is not symmetrical or when both halves of the section convey different internal features.
AS1100 identification of the section.
- The cutting plane is shown on the exterior view as a thick chain line with arrows indicating the viewing direction. Letters (A-A, B-B) identify multiple sections on the same drawing.
- On the section view itself, the cut faces are hatched with continuous thin lines at 45 degrees. Adjacent parts use different hatching directions or spacings to make them distinguishable. Different materials use different hatching patterns (cast iron is shown by widely spaced lines; concrete is shown by triangular aggregate stipple).
- The section view is labelled with the same letters used on the cutting plane (Section A-A).
AS1100 standard symbols. Two examples relevant to a lifting hook and shackle drawing:
- Threaded fastener symbol. A simplified representation of an external thread (a single thin line at the minor diameter for the threaded portion) plus an end view. Used for the shackle pin thread.
- Weld symbol. An arrow pointing to the joint, a horizontal reference line, and a triangle indicating fillet weld with leg size in millimetres. Used at the connection of the hook nose forging.
Markers reward (1) the half-section definition and use, (2) the identification of cutting plane, hatching and section label, and (3) two correctly named AS1100 standard symbols with their function.
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