## First angle projection examples with plotted curves

In orthographic projection, all widths in the end view are equal in size to depths in the plan view, and of course the opposite is true that some dimensions required to complete end views may be obtained from given plan views. Figure 4.21 shows part of a solid circular bar which has been cut at an angle of 30° with the horizontal axis. Point A is at any position along the sloping face. If a horizontal line is drawn through A across to the end view then the width of the chord is dimension X. This dimension is the distance across

(c) Fig. 4.18
(b)
Fig. 4.21

the cut face in the plan view and this has been marked on the vertical line from A to the plan. If this procedure is repeated for other points along the sloping face in the front view then the resulting ellipse in the plan view will be obtained. All of the examples in this group may be solved by this simple method.

A word of warning: do not draw dozens of lines from points along the sloping face across to the end view and also down to the plan view before marking any dimensions on your solution. Firstly, you may be drawing more lines than you need, and in an examination this is a waste of time. Secondly, confusion may arise if you accidently plot a depth on the wrong line. The golden rule is to draw one line, plot the required depth and then ask yourself 'Where do I now need other points to obtain an accurate curve?' Obviously, one needs to know in the plan view the position at the top and bottom of the slope, and the width at the horizontal centre line and at several points in between.

In the examples shown in Fig. 4.22 three views are given but one of them is incomplete and a plotted curve is required. Redraw each component using the scale provided. Commence each solution by establishing

millimetres

the extreme limits of the curve and then add intermediate points.

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### Responses

• DANIEL
How to plot curves orthographic projections?
8 years ago
• Thomas Dery
Which pencils used nd where in ed for first angle projection in dimension line?
4 years ago
• VIGO
How to draw first angle projection using pencil?
3 years ago
• roberto
When drawing orthographic projection are curves inclufed?
3 years ago
• Kacy
How to draw curves in orthographic?
3 years ago
• Rufus Took-Took
How to mark technical drawing first angle projection?
3 years ago
• sandy
How to draw fist angle projection learning?
3 years ago
• welde
How to draw view of isometric drawing in first angle projection?
3 years ago
• Katie Hubbert
How to learn diagram angle progection?
2 years ago
• tom
How to construct a first angle projections?
2 years ago
• biniam
How to project first angle projection on engineering drawing?
2 years ago
• j
How to draw diagrams in orthographic projection using first angle projection?
1 year ago
• yusef
When dimensioning in mm do i use first angle projection?
11 months ago
• philipp
How to show curve on third andgle orthographic?
5 months ago