C&G PowerPoint Setting out curves

Level 3 Diploma in Site carpentry

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PowerPoint presentation

Setting curved mouldings

Unit 307: Carry out second fixing double doors and mouldings



Overview

• Describe methods used to set out curved mouldings• Describe how to bisect angles



Two main categories for curved mouldings

• Roman mouldings which are based around circles• Grecian mouldings which are based around elliptical curves.

The setting out of Grecian curves is more complex and time-consuming.



Intersection of mouldings

• Where two mouldings join is called the mitre.• It is a straightforward bisection of the angle for moulds of the same

size and which are straight.



Bisecting an angle for straight mouldings

Bisection line

Bisection angle

Source: Steve Redfern



Bisecting a line when a straight and curved moulding meet

• When a straight and curved moulding meet the bisection line will be curved.

• This requires a mitre that has a curved cut.• The wider the material the more pronounced this curve will be.• The more obtuse the angle the straighter the curved of the cut will be.



Bisecting curved and straight mouldings to produce the true curved shape

• Draw the plan of the moulding.• Divide up the profile at appropriate points (1 to 8 for this example).• Draw parallel lines out towards the seat of the mitre.• From the centre of the curve draw arcs passing through these points

at the seat of the mitre.• This produces the true shape of the curve at the mitre.• Make a template for both the concave and convex profiles.• Make saddles to fit the mouldings and with the template mark and cut

the mouldings with the chisel.



Curved mitre setting out



Setting out curved mouldings

• To enable the accurate setting out of shaped mouldings a full size drawing needs to be carried out.

• This will require three pieces of information.– The shape required

• Segmental

• Semi-circular

• Gothic– Span (width of the moulding)

– Rise (height of the curved part of the moulding)



Segmental arch

• For a segmental arch of span AB and rise CD use the following method

1. Draw span AB

2. Bisect line AB and find point C and draw bisecting line

3. Measure rise D up bisecting line

4. Draw line BD and bisect it

5. Where lines bisecting AB and BD intersect mark point O

6. With O as centre OD as radius draw the arc ADB for the arch



Mathematical method

• The formula for calculating the radius of a segmental arch is:

D X D ÷ C + C ÷ 2 = RADIUS

C

D

Radius Source: Steve Redfern



Semicircular arch

• For span AB the rise will be half the span.

1. Draw span AB

2. Bisect line AB and find point O

3. With radius AO draw radius



Gothic or equilateral arch

• For an equilateral arch the radius equals the span

1. Draw span AB

2. With A and B and radius AB draw arcs AC and BC



Elliptical arch

• The elliptical arch can be drawn in several ways. Four methods are:– Concentric circle– Intersecting lines– Pins and string– Trammel



Elliptical arch: concentric circles method

• To create an ellipse using the concentric circle method, you will need to know the length of the “X” axis and the length of the “Y” axis

1. Set out the length of the “X” axis – “X” is the longest axis

2. Bisect the “X” axis – open compass out to more than half the length and describe an arc from each end of the “X” axis.

continued…

XX





3. Set out the length of the “Y” axis – “Y” is the shortest axis. Mark off the length of the “Y”, measuring half the length each side of the “X” axis

continued… XX

Y

YSource: Steve Redfern




4. Set a compass to the “Y” radius and describe a circle.

5. Set a compass to the “X” radius and describe a circle.

continued… XX

Y

Y





6. Using set squares, break the circle up into sections. The more sections, the easier it is the draw the ellipse

continued… XX

Y

Y





7. Using set squares, measure out and down from the circle intersecting points

continued…

XX

Y

Y





8. Mark a line joining the intersecting points to form the ellipse.

X

Y

Y




Elliptical arch: intersecting lines method

1. Draw span AB (major axis) and rise CD (minor axis).

2. Form rectangle ABCDE.

3. Divide lines AE and AC into equal parts. The more parts the easier it is to draw the ellipse.

continued…

E

A C B

FD

E

A C B

FD






4. Extend line DC to point G so line GC is equal to the rise.

5. From point G draw lines through points on line AB until they reach points on lines AE and BF.

continued…

E

A C B

FD

GSource: Steve Redfern




6. Now complete by drawing lines for the ellipse.

E

C

FD

BA




Elliptical arch: pins and string method

1. Draw major and minor axis AB and CD.

2. With centre C and radius AE mark points G1 and F2.

3. Place pins at points F1, F2 and C.

4. Place taut string around pins.

5. Remove pin at point C.

6. Place pencil tight up against string and draw ellipse.



Elliptical arch: trammel method

1. Construct trammel having points equal to half the major axis (run) and half the minor axis (rise) from pencil or cutter.

continued…

Source: www.thisiscarpentry.com

Source:




2. Construct base board to take trammel

continued…





Base board using trammel with router attached





Base board set up with pencil




Any questions?

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C&G PowerPoint Setting out curves