AS 1100 Technical Drawing
Instrumental drawings are based on a set on standards that have been globally agreed upon by the International Standards Organisation (ISO). These standards are then tailored to the specific needs of a country depending on such things as the adopted measuring system (metric or imperial), environmental conditions, manufacturing processes and developments in technology. The Australian Standard 1100 (more commonly referred to as the AS 1100), acts as a convention for all engineers, architects, designers, surveyors, pattern makers and other design disciplines to follow. This ensures that the visual communications, products and environments that they design can be manufactured by anyone around the world. These standards include everything from the paper size that is used, the pens or pencils the lines are drawn with and even the type and total number of drawings that are required for any one part or assembly of parts.
The standards offered in the sub-menus of this section of the site are an interpreted and abridged version of the Australian Standards AS 1100.101-1992 Technical Drawing – General Principles. Although the AS 1100 covers all disciplines of technical drawing, especially engineering, some design disciplines such as architecture, apply additional conventions that tailor the technical illustrations and notations to industry requirements. These standards are available separately from SAI global's website or Techstreet.
Dimensioning is used to indicate the overall and individual feature measurements of the product to be manufactured. To avoid any confusion, all dimensioning should be clear and allow a manufacturer or builder to read the plans quickly and without ambiguity.
All necessary dimensions to manufacture the finished product must be shown. No more dimensions than those necessary are to be given.
- Dimensions should be selected and arranged to suit the function and assembly of parts.
- All dimensions should be clear and not open to interpretation. These dimensions are known as 'Functional Dimensions'.
- Drawing should define the form of a part without specifying how the part is to be manufactured. For example, the diameter of a hole is given without indicating if it is to be drilled, reamed, punched or any other production method.
- All dimensions should be arranged for optimum readability. Each dimension should be provided in the view best suited to the feature being dimensioned and refer to visible outlines unless unavoidable.
Projection and Dimension Lines
Projection lines are fictional lines that are 'projected' or drawn out from a line, point, or surface to enable the object's dimensions to be placed outside its outline. This ensures that the dimensions are communicated clearly and the outline of the part is still obvious from a distance. Projection lines are the extremities of a dimension, that is, where the measurement begins and finishes. As indicated in image below, projection lines are drawn using a B style line.
Dimension lines indicate the measurement of the feature being specified. Like projection lines, they should be placed outside of the part outline whenever practical. The image below shows the application of both Projection Lines and Dimension Lines in combination.
The spacing of the dimension lines should be in reference to the character height being used. Australian standards recommends that the first dimension line be drawn 3 times (3h) the character height away from the part outline and 2 times (2h) for all succeeding dimension lines.
Leaders are lines that are drawn with a terminator, such as an arrowhead or dot, to indicate where dimensions, notes, item numbers, or feature identifiers are intended to apply. When leaders are used to
Types of Dimensions
Measurements that are crucial for the operation or assembly of a part or an environment are known as 'Functional Dimensions'. These dimensions must always be inserted onto a component or detail drawing.
When overall dimensions are provided on a drawing it can cause one or more of the intermediate dimensions to become redundant. In this case, the redundant dimension should be removed from the drawing to make an allowance for variations in the manufacturing process. The redundant dimension being removed should not be a functional dimension, that is, it should not be relevant to the product or environment's overall function or assembly.
In cases where omitted dimensions are not required but their inclusion could be useful, these dimensions can be reinserted as auxiliary dimensions. Auxiliary dimensions are shown within parentheses or round brackets.
The following symbols are used to indicate the features of dimensions and to assist in describing the physical form of the part being dimensioned. Symbol proportions relate to the height (h) of the characters being using within the drawing.
Example of Dimensions
Linear Dimensions should be indicated in millimetres (mm). This can be indicated on the drawing by inserting a prominent note, 'DIMENSIONS IN MILLIMETRES' usually within the titleblock. In the case of two units of measurement being used in the same drawing then the note 'ALL DIMENSIONS IN MM UNLESS OTHERWISE STATED' should be inserted. The measurements other than millimetres should then be indicated with the appropriate symbol placed after the numerical value.
Angular dimensions are expressed in degrees. They can be expressed as decimals or in degrees, minutes and seconds.
Methods of Dimensioning
All dimensions within drawings should be completed using one of the following methods;
The unidirectional method requires dimensions to be drawn parallel to the bottom of the drawing sheet, that is, horizontal. To ensure that the written dimension is legible, gaps are left between the written dimension and any surrounding lines such as dimension lines and centre lines.
The aligned method requires dimensions to be placed parallel to the dimension line so that they can be read from either the bottom edge or from the right side of the drawing while avoiding placing any dimensions in the shaded area as indicated in Figure 400 – Aligned Dimensioning.
When several parallel dimensions are projected out from a drawing, dimensions should be staggered to ensure that they are easy to read.
Lines and Line Styles
Line styles and thicknesses are an important component of instrumental drawing. They can indicate the boundaries of a part, a part's hidden features, or the travel path of a machinist's drill, mill or lathe. It is important that the correct line style and thickness is used to ensure your instrumental drawing is not ambiguous to anyone involved in the manufacture or construction of a product or environment, the production of instructions or the use of the product or environment. The advantage of changes line thicknesses can be seen when a drawing requires lots of dimensions, the thicker outline stands out from thinner dimension lines.
Line Styles and Thicknesses
Line Style Example Purpose Continuous - Thick
To indicate visible outlines
Continuous - Thin
Fictitious internal lines
Continuous - Dashed Hidden Features Chain line - Thin Centrelines
Material for removal
Chain line - Thick at ends and at change of direction To indicate a cutting plane for sectioned views
The thickness of lines are based on the size of the drawing sheet using used. The table below shows the appropriate line thicknesses applicable to the various sheet sizes.
Sheet Size Line Type and Thickness (mm) A B C D E F G H J K A0 0.7 0.35 0.35 0.35 0.35 0.5
0.35 0.7 0.35 A1 0.5 0.25 0.25 0.25 0.25 0.35 0.25
0.5 0.25 A2, A3, A4 0.35 0.18 0.18 0.18 0.18 0.25 0.18
Line Presentation in Technical Drawings
The presentation of lines in instrumental drawings is important as it maintains clear communication of intention and avoids ambiguity. It is therefore important that the following guidelines are used when drawing the applicable line styles;
The scale of line thickness and length of dashes and spaces should be uniform across a drawing.
The thickness of line(s) used should not become thinner than 0.18mm if the drawing sheet was reduced to A4
When indicating centre points, centreline dashes should intersect at the origin of the feature
Centrelines should extend a small distance past the feature of the drawing
Centrelines should cease at any other line of the drawing
Chain lines that indicate a cutting plane should begin and end with long dashes as best fits the drawing
Chain lines that form an angle should cross or meet at the corners
Dashed lines should start and end with dashes in contact with the visible or lines from which they originate
If a dashed line meets a curved line tangentially, then it should be with a solid portion of the line
There are occasions when a drawing cannot provide adequate information to indicate the form of an object or environment. In these circumstances an additional view must be drawn in combination with, or instead of, the normal outside views. The new view is called a sectional view.
Sectional views represent a view that has been sliced along a cutting plane to reveal a product or environment's inner detail.
Whenever a sectional view is drawn, the remaining solid or material components are indicated by hatch lines. Drawn at 45°, hatch lines should be drawn as thin lines and evenly spaced over the entire part.
Spacing of Hatch Lines
Hatching lines should be evenly spaced and as best fits across the object or component of the part or environment being sectioned. If the hatching coincides with one or more sides of the part then an alternative angle can be used.
Types of Sectional Views
Thin sections are used to show the thickness of thin parts without having to draw the material thickness out of scale. To ensure that thickness of each part is communicated clear a minimum gap of 1mm between parts is shown.
Any part or environment that is symmetrical can be drawn half sectioned.
Local sections can used to avoid showing a separate sectional view. The local area being sectioned is indicated by a continuous thin irregular line.
Successive sections can be drawn as removed sections when, through lack of space, the sectional views cannot be shown in normal projection.
Revolved sections are used to the cross section of an arm, rib, spoke, or bar. Revolved sections are shown by drawing the cross sectional view of the part in position with the adjacent detail drawn around the revolved view.
Removed sections are similar to revolved sections but they are drawn outside of the original part. They can be drawn adjacent to the original part or completely away from it. If drawn completely away from the part, both the section and the cutting plane must be clearly indicated to avoid confusion.
Exceptions to Sectioning
As with most rules there are exceptions. When a section plane cuts parts such as bolts, ribs, nuts, rivets, shafts, spokes, or wheels then these parts are not sectioned but shown in an external view.
Types of Drawings
When a product or environment has been designed, it is then prototyped or produced by a manufacturer or constructed by a team of builders or engineers. To assist in the creation of the product a set of plans are required. These plans enable the people whose job it is to create the design to do so in a way that meets the designer or client requirements. In order to do this, a drawing method that can illustrate to someone the size and shape of product's form, how many parts the product has and from what material each part or component will be made or constructed from is required.
What drawings are needed?
When a designer chooses to have a product manufactured they must provide the manufacturer or builder with enough information to make each individual part and assemble the parts to construct the overall product or environment. In these circumstances a complete set of 'Working Drawings' are needed. A set of working drawings consist of 'Detail Drawings' and 'Assembly Drawings'. In some occasions a 3-dimensional pictorial drawing can also be included to provide additional information if required.
Detail drawings are used as a primary reference for manufacturing an individual part. They must show all of the detail required to manufacture an individual component including a suitable number of fully dimensioned orthogonal views. It is convention for detailed drawings to contain only one part per drawing sheet; however, multi-detailed drawings can be used when it is more convenient to show a small number of simple individual parts on the same drawing.
The following information is included on a detail drawing;
- Dimensions and instructional annotations
- Drafting standards used (AS 1100)
- Name and Title of the Drawing
- Drawing NumberUnit of measure (mm)
- Tolerances where appropriate
- Surface texture finishes
- Special Treatments (heat, metallic coatings, paint)
- References that reference a part to its particular sub-assembly
- Type of Material used (Steel, High Speed Steel, Aluminium, Copper, Brass, Polystyrene, ABS)
- Names of drafter, checker, approver, the dates on which the drafting and other procedures occurred
- Zone reference system to help locate areas on a drawing
- Size of the drawing sheetName of company or department
- Drawing sheet reference, eg. 1 of 2
Assembly and Sub-assembly Drawings
An Assembly drawing shows how all the individual parts fit together to make an assembly. They are drawn using an arrangement of orthogonal views and cut sections. To show how large complex parts are assembled, large assembly drawings are generally made up of smaller sub-assembly drawings. In the case of a mountain bike for example, the bike's frame would be considered a sub-assemble, the gear cogs and chain considered a separate sub-assembly and so on. All of these sub-assemblies would then assemble to form the finished mountain bike assembly.
There are two styles of assembly drawings used; General Assembly Drawings and Working Assembly Drawings
General Assembly Drawings
General assembly drawings are orthogonal drawings that are used to identify the individual components required to make up an assembly or sub-assembly. When drawing a general assembly the following points should be taken into account:
- Only the necessary views required to clearly describe how the parts fit together and how the sub-assembly functions should be shown. These views should include a sectional view to avoid the use of hidden lines.
- Annotations and dimensions that relate to the function of the sub-assembly are provided.
- Individual components are identified by the use of leaders from the part and numbers enclosed within circles or balloons.
- A Parts list sorted by the part number in the drawing identifies each part, its drawing number, and quantity. This list should also include any off the shelf parts used within the sub-assembly.
- Assembly and sub-assembly drawings do not need to list information about the manufacture of individual parts. However, information about how a sub-assembly is to be assembled or important dimensions that could affect its assembly can be included.
Working Assembly Drawings
Working assembly drawings are a combination of working drawings and assembly drawings. They are typically only used where the drawing of the individual components, dimensions and the assembly of parts can be drawn on the same drawing sheet without ambiguity. Such drawings are typically only used in industries like furniture design where join details are provided in enlarged separate detailed drawings.