Page 1 of 5. ENGINEERING SKETCHES INFORMATION SHEETS MEL02INF2430 v1.1 HEALTH & SAFETY REQUIREMENTS

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1 Page 1 of 5 Competenz - N Z Engineering Food & Manufacturing Industry Training Organisation Inc. ENGINEERING SKETCHES INFORMATION SHEETS MEL02INF2430 v1.1 HEALTH & SAFETY REQUIREMENTS RECORDING REQUIREMENTS: Record the results of your work on Task Worksheet MEL02TWS09 v1.1 REFERENCES: This document relates in part to the requirements of Unit Standard 2430 v5 DRAWING AND INTERPRETING ENGINEERING SKETCHES The purpose of good sketching in an engineering environment is to effectively and accurately communicate the job requirements using common engineering conventions, and quick, cost effective methods. Sketches are usually done on note pads at the workbench, on blotter pages and the back of envelopes in the office, and even on pie packets and chip bags during lunch breaks. The engineers pocket notebook is an excellent place for making sketches to assist with component construction, job layouts and machining methods. The completed sketch should provide sufficient clarity and detail to allow immediate machining, fabrication and assembly of the component or product. Sketching Equipment and Aids Engineering sketches are made using basic equipment including pencils, colored ball-point pens, rules and erasers. Boilermakers chalk is often used when sketching on steel plate or on the concrete workshop floor. Where time permits, simple drawing equipment including compasses and setsquares are used to aid the development and accuracy of the sketch. Common Line Types and Dimensioning Engineering sketches use a few basic line types to define and explain the features of an article. These are: Construction Lines: Very light line used to establish proportions and locations Outlines: Heavy line used to define the overall shape, size and features of an article or component Hidden Detail Lines: Used to define details hidden from view in the sketch Centerlines: Used to define the location of holes and may be extend to be used for dimensioning Dimensioning lines: Medium-weight line used to define the size of an article or component and locate its features Dimensioning arrows heads are proportioned 3x long and 1x wide. Ø 3 x Ø56 Ø 3 Ø34 Dimensioning leader lines extend from the article outline but do not make contact. Ø23 Major dimensioning starts from common datum surfaces, edges and points. R11 R6 Ø12 Dimensions follow the angle of the dimensioning line and are positioned centrally along the line length. The dimensions should be readable from the bottom right-hand side of the page. HANDY HINT; Only the dimensions needed to define the features of the finished article should be shown on completed sketch. Circles and circular objects are dimensioned by stating the diameter. There are a number of common ways of dimensioning radii and circles, depending on the size, location and orientation of the object. R7

2 DEVELOPING OBLIQUE PICTORIAL PROJECTIONS Oblique pictorial projections use three basic lines to construct an oblique view of an article; Horizontal, Vertical and Sloping Oblique construction shows the true size and shape of one side or the end of the article which is nearest the viewer, while the other sides are shown at an angle, usually º. HANDY HINT; use set-squares or quad-paper to construct the sloping lines. 90º Oblique º Step-1; The side of face of the article which will show the most detail should be sketched as the front surface using horizontal and vertical lines. Step 2; Add the sloping edges from the corners at a suitable angle, usually º. Step-3; Connect the far-end or back edges to complete the basic article outline. Step 4; Add in detail such as holes, spigots or grooves. Shading may be used to provide clarity of appearance. 3 Step 5; Dimension the sizes and features required for production. Importation information such as quantities required, material type, tooling, jigs and fixturing requirements can be added as notes. HANDY HINT; Use square construction boxes with intersecting centerlines as a guide for sketching circles and other objects. Ø 3 HANDY HINT; The proportions of an article sketched in oblique projection often appear to be distorted. To correct this apparent distortion, the length of the º sloping lines can be shortened by half. This is know as the Cabinet Method. When sketching circles in oblique projections, it is easiest to place true circle shapes on the front face of the article. However, when sketching circles on the distorted oblique faces; 1) The circle must fit into a square construction where the sides of the square are the same size as the diameter of the circle, and 2) The four arcs of the distorted circle must touch the square construction box where the centerlines intersect the edges of the square.

3 DEVELOPING ISOMETRIC PICTORIAL PROJECTIONS Isometric pictorial projections use two basic lines to construct an oblique view of an article; Vertical Lines and 30º Sloping Lines º Isometric construction has the advantage of presenting undistorted proportions and shows the article turned so that a corner or edge is nearest the viewer. HANDY HINT; use set-squares or quad-paper to construct the sloping lines. 30º º º 30º Isometric Step-1; Sketch the vertical edges of the front face, followed by the 30º lines for the horizontal edges. Step 2; Add the sloping edges from the corners at 30º. Step-3; Connect the back edges to complete the basic article outline. Step 4; Add in detail such as holes, spigots or grooves. Shading may be used to provide clarity of appearance. Step 5; Dimension the sizes and features required for production. Importation information such as quantities required, material type, tooling, jigs and fixturing requirements can be added as notes. Ø 3 x 3 HANDY HINT; Use square construction boxes with intersecting centerlines as a guide for sketching circles and other objects. When sketching circles in isometric projections; 1) The circle must fit into a square construction where the sides of the square are the same size as the diameter of the circle, and 2) The four arcs of the ellipse must touch the square construction box where the centerlines intersect the edges of the square.

4 DEVELOPING PERSPECTIVE PICTORIAL PROJECTIONS Perspective projections are used as a method for constructing realistic representations of an object article, component or final assembly. Single-Point Perspective (in a similar manner to oblique projection) shows the true size and shape of one side, end or face of the article which is nearest the viewer, with the lines extending away to meet at a single vanishing point at eye level on the horizon. The article is placed at a convenient distance from the vansihing point, and above, below, or on the horizontal eye-line, depending on the desired outcome and the need for clarity and detail. Single-Point Perspective Eye Level Horizon Line Step-1; The side or face of the article which will show the most detail should be sketched as the front surface using horizontal and vertical lines. Construction line are extended back to the vanishing point. Step-2; Add features to the front face and define the depth of the article by completing the outline. HANDY HINT; The further an article sits from the vanishing point, the more realisitc the article will appear. Ø 3 Step-3; Add detailed features to the other faces. Define the article outline by extending construction lines back to the vanishing point. 3 Using perspective projection allows the design-engineer to provide a realistic portrayal of how a finished product will look to the machine operator and the customer. Step-4; Shading, hidden-detail lines, notes and dimensioning can be added for clarity. Two-Point Perspective (in a similar manner to isometric construction) shows the article turned so that a corner or edge is nearest the viewer, with the lines extending away to meet at two vanishing points at eye level on the horizon. The article is placed at a convenient distance from each of the vanishing points, and above, below, or on the horizontal eye-line, depending on the desired outcome and the need for clarity and detail. Two Point Perspective HANDY HINT; Vanishing points should be widely spaced to produce a realistic representation and may need to be extended beyond the edge of the page.

5 DEVELOPING THIRD-ANGLE ORTHOGRAPHIC Orthographic projection is used where an article, component or assembly is too complex or detailed for all the information to be communicated accurately in a single pictorial view. The Main Elevation is usually the side or face which shows the most detail. The Plan, which is shown on the drawing directly above the Main Elevation, is the top (or birds-eye) view of the article, component or assembly. The End Elevations are the views from the left-hand-side and the right hand side of the Main Elevation and are shown from that position. The dimensions on an orthographic projection are constructed as follows; Main Elevation: Lengths and Heights Plan Plan: Lengths and Widths L.H Side End Elevations: Heights and Widths End Elevation HANDY HINT; Orthographic projection is an ideal method for making sketches of complex and detailed items such as equipment and machine components. 3rd-Angle Orthographic When a component is held at eye-level, the vertical faces are the Elevations. When looking down from above, the view is called the Plan. Datum Line Plan Horizontal Projection Lines Main Elevation º Primary Projection Line R.H Side End Elevation Vertical Projection Lines Main Elevation RH End Base Line Step-1; Extend base and datum lines from the main elevation. Use vertical, horizontal and a º diagonal line to project the heights and widths between the elevations (shown in red). Step-2; Add detail such as holes and spigots. Use hidden detail lines and centerlines for clarity and to establish locations. Avoid unnecessary sketching and page clutter by projecting and dimensioning only the elevations required to provide the detail necessary for completing the job. Step-3; Dimension the sizes and features required for production. Importation information such as quantities required, material type, tooling, jigs and fixturing requirements can be added as notes. Ø 3 3