How to Make Your Own Sundial

Instructions for making an equatorial sundial

1. To make an Equatorial dial of 500mm diameter and set to your latitude you require a Polar ring and 2 half circumferences for Meridian and hour bands.
2. Buy 2 x 2m lengths of 25mm x 3mm aluminium, 1 x 4mm lengths of threaded rod and 1 x 6mm tube sleeve from a builders merchant.
3. To calculate the circumference of Polar ring – 500mm x 3.14 (pi) = 1,570mm.
4. Mark, cut and roll the Polar ring by finding a sturdy round object to wrap the metal round.
5. To establish length of Meridian and hour bands, the calculation is circumference plus twice the width of the Polar ring (25mm x 2 = 50 + 1570mm = 1620mm).
6. Cut 1620mm length in half to create the Meridian and hour bands, drill hole in centre of both and drill 2 5mm holes 12.5mm from each end 12.5mm.
7. To calculate hour increments, take 360˚ ÷ 24 hours = 15° per hour. Take circumference 1,570mm ÷ 360° = 4.36mm per degree x 15°= 65.4mm per hour.
8. Starting from the centre hole, create hour marks 6 each side at 65.4mm intervals and partially drill each.
9. The sundial's angle is set to your latitude and is the distance between hour band and Meridian's fixing point: circumference ÷ 360° x latitude. For my latitude, the calculation would be:
   1,570mm ÷ 360° = 4.36mm x 51° = 222mm.
10. Drill base fixing of Meridian 222mm from centre hole.
11. Roll Meridian and hour bands into semi-circles and bolt together at 90°.
12. Place Polar ring on flat surface mark at 4 equal parts. Place bands over Polar so Meridian straddles the join. Drill and fix through existing holes.
13. To fit gnomon Drill hole in centre of Polar and Meridian inter-sections at top and bottom.
14. Cut tube into 2 x 250mm lengths.
15. Insert threaded rod through Polar hole, and through 250mm length of tube, place a penny washer on threaded rod and slide second tube through Meridian and Polar hole, tighten top and bottom with fixing.
16. Fix dial to base with screw and turn to face due South and check time, Noon is GMT.
17. Spray paint dial and partially re drill hour marks to remove paint.