Orthographic  Drawings

Orthographic projection is the technique most commonly used in the furniture and building industry in England and the UK for working drawings.   There are two main methods of laying out the views on the drawing so that most of the  information is available to construct or manufacture the subject.    The craftsman or operator may well have to refer to various scales, Schedules and a Specification sheet to complete the job to the architect or designers and ultimately, the customer’s, wishes.    These main techniques or views are:

·      Third Angle projection (TAP) which is widely used by North America and in the United Kingdom by Engineers, and

·      First Angle projection (FAP) which is the European (less Dutch) method and the method recommended by the furniture, building and other woodworking industries.

They are a pictorial method of illustrating a project so that all details are shown to build, construct or manufacture the subject.   They are drawn in various scales depending on the detail and content required.   This paper will only discuss FAP.    

Orthographic Drawings (FAP), have a minimum of three views of the subject so that details  all sides of the object may be scrutinised.   If there are details differing on front and back or top and bottom, these views may be added in the respective places.    Because the system or technique is geometrical there are rules or conventions that need be followed in order to interpret the drawings correctly.  

Most students who have followed Technical Drawing or Engineering may well have been familiar with orthographic drawings but they usually were taught the Third Angle TAP rather than FAP that is required for woodworking drawings.   This sometimes leads to confusion but they may or may not be pleased to know that woodworking drawings are often drafted with a mixture of the two methods.    This is not a disadvantage because the designer or illustrator often adds enhancement to their drawings to highlight or stress a particular feature.     Because of this, drawings differ from architect to architect and designer to designer with each person using favourite and slightly different techniques that the experienced builder eventually picks up.   During this course we try to standardise on the basic techniques and introduce various popular techniques that they well find in drawings and how to interpret them.

The following explanation of Orthographic Drawings (FAP) will be based on the  ‘F’ frame shown below.   To  illustrate to you the reader, what it is, it is drafted in isometric projection.                       

You can see that it is an upright with a horizontal member at right angles at the top and a second shorter member lower down.  You will be able to see that both joints are ‘bridled’ but they differ, in the way that they are fitted.

You cannot see the far vertical section, the rear elevation or indeed the view from below.   If this detail was required you may well need additional drawings to show this.   An orthographic drawing overcomes these problems and although requires more views, keeps to simple lines.

The object shown may be viewed from six different views but the main view that is readily recognisable is the front elevation and is the view one would recognise a door or window frame from or indeed the front of a building.     

Notice  the dimension lines that are stretched  between an extension of the construction line.    These lines are usually solid with neat arrow heads or hashes to show extremities.  The figure showing dimension and the unit of measurement, i.e. ‘mm’ is shown above or alongside not between broken lines.

You will notice that dotted lines have been added.    This is extra detail is to show detail of the jointing and other hidden features.

To complete the information and dimensions of the subject, views of the horizontal and vertical sections are shown alongside and below the front elevation.                                          

An outline of an orthographic projection of the ‘F’ Frame is now shown to the right.

The dimension lines need not be repeated for each view where the views line up top and bottom.

Note the way internal measurements  are shown neatly and how the extension lines clearly show the extent of the dimension.    

The width and thickness of the material may be shown in the specification.   Usually a cross section of the material is shown from a ‘Section line’, this will be explained later.

This example shows only one horizontal elevation and one vertical elevation.   If there are other unseen details on the other planes then it would be prudent to show them using additional views.

Designers try to keep all the detail compact on one sheet to avoid too much detail that may confuse rather than inform.  The author tries to get drawings on one sheet of either A4 or,  A3 if necessary.   Remember, a lot of information is also available from the specification and the width and thickness of material is available from Cutting Lists.                

 The symbol for Orthographic FAP is:  

How to interpret the views

The different views seek to show the operator all the information available to construct the object.   Perhaps if you have already use to Third Angle, First Angle may confuse for a while.   In TAP the elevations are on the same side they are viewed from.   However, in FAP the elevation is placed on the opposite side.  This is because the view is ‘projected’ through from the viewed plane.   You can imagine the plan being picked up and placed through 90 degrees.   This is the view you are looking at and now it may seem to make sense.  Refer to the following illustrations:   

Section Line