With the bamboo cut and the nodes drilled, the next step in our bamboo wind chime plans is to cut the holes in the top circle for the tube strings. In this step, we're assuming an 11-1/2" diameter hardwood circle and five tubes. If you decided to use a different diameter circle at the top or more (or less) tubes, you'll need to adjust the math in this step accordingly.
With a straight-edge, mark a straight line from the center hole on the large hardwood circle to the edge. Next, grab your compass and widen it to a 5" radius. With the width exactly 5", place the point in the center hole and scribe a 5" radius circle all the way around the piece.
Now, with your tape measure, begin where the straight line meets the circle, and measure 5-7/8" to one side, finding the point where this distance meets the circle. Make a mark at that point, intersecting the circle. Continue around the circle, making marks every 5-7/8" (on the circle). When you've completed the fifth mark, verify that the distance from mark 5 back to mark 1 is 5-7/8". If so, you successfully scribed the five equidistant points on the circle (72-degrees from center for each line).
Next, measure the diameter of each piece of bamboo tube at the top. You'll be ordering the bamboo sequentially around the chime from longest piece to shortest.
Divide the diameter of the longest piece in half. Mark this distance on either side of the first mark on the circle. Where these two marks meet the circle will be the points to drill through holes for the strings of the longest tube.
Repeat this step with the other four tubes.
After the holes are drilled, this would be the ideal time to apply finish to the three pieces of hardwood. You may paint the pieces, or use stain and polyurethane, whichever you choose.