Geometry

Shopfitters need to be able to do some basic geometry like bisecting angles and setting out some basic shapes such as hexagons ( 6 sided) and other polygons.In a workshop you will usually use a trammel and straight edge to set these out full size, ususlly on a piece of ply or thin MDF. Modern factories with point to point machinery can set the shapes out on a computer set the material in the bed of the machine and the machine will make a perfect job of any shape if its set out correctly. But not all businesses have thes facilities available so it is good practice to be able to bisect angles and set out set different shapes out using a range of traditional methods

On this page you will find some demonstrations of how do this in different ways. Lets start by bisecting a line. Bisecting a line means dividing it exactly in half.

Bisecting the line geometrically will produce a perpendicular line that is 90| degrees to the original. Watch the power point below to see how it is done, then download print out and try the activities in the document below. Bisecting lines exercise: Bisecting an angle means dividing it evenly in half (1/2) as you would for a mitre joint. A mitre angled bisected

An acute angle bisected

Check out the powerpoint demonstration to see how its done easily.

Download and try bisecting the angles in the Bisecting angle exercise document below.

Sometimes Shopfitters and Joiners have to set out elliptical shapes. Sometimes for display counters and sometimes for arched windows. An ellipse is an oval shape with no regular radius. There are several methods used to mark out an elipse. 1. the Pins and String method 2. Concentric circles method
 * Setting out an ellipse**

Take a look at the powerpoint below to see a demonstration on setting out an ellipse in the workshop using the pins and string method.

View the powerpoint below to see how to set out an ellipse using the concentric circle method. For more information on drawing and setting out ellipses try these links:

[|four centred ellipse and concentric circle method] Now watch this video on using a simple jig for routing an elipse: media type="youtube" key="tgT5deym1Qk" height="310" width="378" Thereare other youtube videos demonstrating the cutting of elipese and circles: try this youtbe search: []

Setting out polygons
Probably the easiest is setting out a hexagon in a given circle. in a hexagon all angles are equal and the length of each side is eaqual to the radius of a cirlce.

View the power point presentation then try doing it your self with a simple compass, ruler and pencil.

You mIght like to watch this video to see how to set one out with a compass on a piece of paper. media type="custom" key="23395514"

It often depends upon the dimensions you are given as to the best method for setting out polygons. In the power point presentations below you will find a number of solutions. The first one deals with setting out an octagon in a given square. Regular octagons have parallel sides and are equal distance apart so it is easy to cut them from a square. Its the setting out that can be tricky. Watch the presentation to see how easy it is. Remember accuracy is the key in all setting out.

Sometimes you will only be given the length of one of the sides of a regular polygon. Other shapes such as pentagons (5 sided), heptagons (7 sided) and others can be difficult and may require significant time to set out. View the power point below to see how to set out a polygon when you only know the lenght of one side.

you can watch this You tube presentation also to see how its done. media type="custom" key="23395524"