Here's a simple no-math way to verify your wedge's accuracy using Woodturner PRO.
To follow the above example, if you want a 12" long wedge with the S.E.L. 3" or more. Do the following:
- Start Woodturner PRO and change Row 1 from a Disk to a Flat
- Set the Outside Diameter to 60" and the Inside Diameter to 36" (if turned, this would give a wall width of 12", but the actual trapezoid will be slightly larger because it won't be turned.
- Click the Ring View and scroll to the bottom of the page where the legend containing the calculations appear. You'll have to do a lot of scrolling and make sure the percentage at the top of the page is 100% so you'll be able to read the legend.
Three of these measurements are all you need:
- Segment Edge Length - 3.14"
- Segment Inside Edge - 1.89" (this is the edge opposite the Segment Edge Length. I actually added this measurement purely for this purpose but I may be the only one that has ever used it)
- Board Width - 12.02" (this is the actual measurement of how long the wedge should be.
You can vary the outside and inside diameters to give you a wedge with more or less width. Just make sure that the inside diameter is 24" less than the outside diameter.
I use this process to verify that my cutting angle is correct for making segmented sculptures. If I'm cutting a 3" 'segmented log' into slices that will make a 90-degree angle with 12 slices, I make a ring in Woodturner PRO that has 48 segments, has the outside diameter I want, let's say a doughnut that has a 12" outside diameter and an inside diameter of 6" (to yield a slice that is 3" in diameter). Now I cutoff the end of the log and then rotate it by 180 degrees and make make my second cut that will leave an outside slice width of .79" (the Ring View: Segment Edge Length). Now if I measure the narrow edge of that slice, if it is .39" (the Ring View: Segment Inside Edge), I know that my cutting angle for that slice is a perfect 3.75 degrees. If I make 12 of these perfect slices and glue them together, the angle of the 12 slices will be a perfect 90 degrees.
The following sketch shows a sculpture that needs 12 of these 90 degree corners and some straight runs:
