TURNING A FIVE-SIDED
POLYGON TEA-LIGHT
December
2015
Polar Co-ordinate Graph Paper
7
5
Polygons for Tea-Lights
Drawing and Layout
Cutting
Mounting methods on the lathe
Turning
Sanding
Finishing
Club Challenge
Open Shop June 25th @
Peter Tkacs Shop
HOW TO LAYOUT A
POLYGON
•
Start with a square blank
•
Find the center and draw a
circle
•
Measure the diameter
•
Calculate the chord length
•
Draw and cut the chords
THE KEY FORMULA
(THE MATH)
A=D*Sin(180/N)
A= The Chord length
D= The Diameter
N= The number of sides
a = 2Rsin(180 / n)
a
a= length of chord
R= radius of circle
n= number of sides
2R=6.50
180/5=36
sin(36)=0.588
a=6.50*0.588= 3.82
R
5 Sided Polygon
a = 2Rsin(180 / n)
a
a= length of chord
R= radius of circle
n= number of sides
2R=6.50
180/7=25.714
sin(25.714)=0.434
a=6.50*0.588= 2.82
R
7 Sided Polygon
THE MAGIC NUMBERS
FOR 5 AND 7 SIDES
•
5 Sided Polygon — Diameter X 0.588
•
7 Sided Polygon — Diameter X 0.434
LAYOUT FOR 4, 6, & 8 SIDES
•
4 Sides - Obvious - do nothing
•
6 Sides - The radius of the circle is the length of the arc.
•
8 Sides - Start with a square block. Set the compass
length from the center to a corner and mark arcs from
each corner along the square. Draw lines between arcs.
LETS GIVE IT A TRY