By letting someone else do it ;-)
The easiest way is to use software written for the job.
See Kevin Neelley's "Turned Wood" web site for one example:
He draws the thing full size and then measures off the drawing. He is good with math but thinks the drawing has lots of advantages.
Bill
Draw a 7-3/4" circle on a piece of paper. Decide how many segments you want to use. Lets say you want 8 segments. Divide the circle into 8 equal parts and measure off of your drawing. If you want to use more segments just divide the circle into more equal parts. Or try the woodturner pro software. With the software you don't even have to know how to add. :-)
Bob, Naugatuck Ct.
Check out
Hello Moyo,
As several people have stated, the easiest way is to use one of the segmenting software packages. I've used a couple of them with good results. However, I did more segmenting working from a drawing. Here is how I did it:
I used a piece of 1/4" grid paper with the light blue lines and sketched the bowl shape that I was interested in doing. You only need to draw half of the bowl. I always used 3/4" boards to make my segmented rings, so it was easy to start at the bottom (foot of the bowl), mark up three squares and draw a line through the bowl shape. Continue doing this until you run out of bowl. You have just laid out the segmented rings.
Now, take a pencil compass and put the point on the centerline and set the pencil to touch the outside of the bowl. Draw a circle with this setting. Decide how thich you want the bowl wall and reduce the setting of compass to touch the inside wall point and draw another circle. You have now constructed the inside and outside dimentions of your bowl at that point. Decide how wide the board will be from which you'll cut the segments. I used to use 1-1/2" boards for my segments. Eyeball a mark between the two lines. Then make marks 3/4" either side of the center line of the wall thickness. With your compass, draw circles through each of those 3/4" marks. Now, draw horizontal and vertical lines through the center of the of the circles. You've now divided it into four segments. To get to 8 segments, divide each of these 1/4th segments into half. To get to 16 segments, divide the 1/8 segments in half. Then draw a line perpendicular to a radius line that bisects one of the segments. Now draw perpendicular lines to this line that touches the inner and outer circles. You have now drawn one of your segments. Take you measurements from that to cut the segments for that circle.
Repeat this for each ring of the bowl and you've done what the software can do in a couple of minutes. If you're careful on your layout, everything will work our very well.
I hope this is clear.
Fred Holder
Moyo, That was the same question I had over a year ago. The advice I got was to buy a book on segment setup and turning. I got mine off E-BAY for less then form a book store. I have gone back to that book several times and read it over. They have drawings and charts already figured out, copy them and take it to the shop where you need it.
This is the formula to figure segments. Diameter x 3.1416 = circumference. Divide by the # of segments = length. For example. 7" x 3.1416 = 21.9912 divide by 12 = 1.832 is the length of your segment. This is for tip to tip. You can go to my segmented site for more instructions.
Hi George, With all due respect using Pi in segmenting introduces error. The reason is as you know Pi is a measure of the circumference of a circle.When we build a segmented ring we are stepping around with straight lines. The segments have to be slightly longer to acomplish the same diameter. While a ring with a lot of segments won't have a substantial error a ring with fewer segments will have more of an error. Draw a ring with a smaller amount of segments then do the math and you will find the pi method results in a shorter segment length thus a smaller finished diameter. In some designs enough error to cause major problems.
Bob, Naugatuck Ct.
Yes, that method will produce a 7 inch ring at the segment tips and not at the centres which is what I assume is wanted.
To expand this thread a little, does anyone know of a computer software program to make these calculations, to run on a Risc PC instead of windows. Dave Lawson Redditch UK
There was a fellow on the KC woodturners site who had a computer program for sale. Can't remember his name but he did the fancy segmented bowls shown on the site.
InspirePoint website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.