Basic Geometry

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The curved edge is produced through a classic geometric construction exercise.



Step 1
Set spring-loaded dividers on 20mm's.
R20 stands for 'Radius 20 millimetres'
From the top right-hand corner scribe an arc.
The points at which the arc bisects the edge
of the metal plate are labelled A & B in the
diagram above and the arc is shown in blue.









Step 2. Scribe an arc from each of the points A & B. This is shown in red in the diagram above. The point at which the two arcs intersect is labelled point C.
















Step 3. Place the point of the dividers on point C and scribe an arc which passes through both points A and B. This is shown in green in the diagram above. The dividers should remain set at 20mm throughout.
Use tin snips to cut along the line to produce the curved edge and finish by smoothing with a fine file.

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