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Graphic Communication

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Isometric Views are one of the forms of 3D views that you need to know about in the Standard Grade Graphic Communication course. This type of drawing shows the length, breadth, and height of the object being drawn. An isometric is drawn with a corner closest to the viewer. All vertical lines and all lines angled back at 30 o can be measured accurately. No other lines on Isometric views can be measured.

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If you are sitting an SQA Credit paper in Graphic Communication, you will be required to know how to draw isometric views with curves. This type of drawing is always included in the final paper each year. The table on the following slide shows when each type of drawing was used and how many marks were allocated to it. You will need to know how to draw full and part circles and also sloping edges and surfaces. The ability to be able to answer questions about isometrics will be a great help in letting you reach the pass mark in the Credit exam paper. If you are sitting the General paper you will need to know how to draw Isometric Views, although they will not normally include curves and circles, but will include sloping edges and surfaces.

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YEARSubjectNUMBER OF FULL CIRCLES NUMBER OF PART CIRCLES TOTAL MARKS FOR QUESTION % of DA mark available 1991 Electronic Game Salt Dish (sect) 0000 4040 15 12 21% 17% 1992 Disc Box (exploded) 001826% 1993 CD Player111826% 1994 Staple Gun021420% 1995 Torch101521% 1996 Putting Aid011826% 1997 CD Player111826% 1998 Label Machine101623% 1999 Slide Projector101826% 2000 Speakers111623% 2001 Bathroom scales111623% 2002 Coffee maker111623% 2003 Cup holder101521%

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YEARSUBJECTEXPLODED TOTAL MARKS FOR QUESTION % of DA mark available 1991 Fireplace Prism - Box (sketch) Yes No 12 8 17% 11% 1992 BracketNo1014% 1993 Plant Pot HolderYes1622% 1994 1995 1996 TorchYes1521% 1997 BoxYes1217% 1998 Plant Pot Stand (exploded) Yes1622% 1999 2000 Burglar AlarmNo811% 2001 2002 2003

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Start the isometric circle by drawing the front elevation and the plan of the cylinder to be drawn.

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Choose a suitable point ‘X’ on the elevation and plan and a suitable position to start the isometric view. x x x Draw an isometric crate to fit the isometric view into. Use 30 o and vertical lines for the angles of the lines. The overall size of the crate should be the exact size of the isometric view to be drawn.

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Draw centre lines on the isometric view. Use 30 o and vertical lines for this. x x x

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Divide the orthographic circle into 12 equal parts using 30 o and 60 o lines generated out from the centre. x x x 1 12 11 10 9 8 7 6 5 4 3 2 Number each of the points where the generators cut the circumference of the circle – usually done in the same format as a clock.

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Project points where generator lines cut circumference of circle down and up to horizontal centre line of circle. x x x 1 12 11 10 9 8 7 6 5 4 3 2 Measure horizontal sizes of projected points along centre line with compasses and transfer these sizes onto 30 o isometric centre line. Project vertical lines through these points so that circumference points can be found.

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Using compasses, measure the vertical distances from the centre line up and down to each of the points on the circumference in turn. Transfer each of these dimensions onto the isometric view. Number each of the points. x x x 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2

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Draw a smooth curve through each of the points to show the circumference of the isometric circle. x x x 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2

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To show the thickness of the cylinder in the isometric view it is necessary to project each of the points found back at 30 o. x x x 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2 Measure the thickness of the cylinder on the plan using compasses and transfer these sizes onto the isometric. (In this case all of the sizes are the same but this may not always be the case). It is not necessary to transfer all of the dimensions as all of the points will not be seen at the end – however if in doubt it is better to transfer all and then only use the required ones.

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It is necessary to find two final points – the tangent points - to indicate how far out past points 4 and 5 and points 10 and 11 that the curve passes. This can be done in two ways – by finding points A and B on the elevation and transferring these points to the isometric in the same way as points 1 to 12. x x x 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2 A B A B – or by drawing diagonal lines on the isometric to find where the corresponding points occur on the front curve in the isometric. These points can then be projected back and measured as before to find the final positions. Finally, draw a smooth curve through each of the points found.

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To finish the drawing darken the required part of the outline of the curve. x x x 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2 A B A B Complete the two edges to join the two curves together.

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This is the final Isometric View of the cylinder. x x x

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Department Of Technical Education

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