How do you calculate

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Forum topic by Jack Lewis posted 08-26-2017 10:48 PM 857 views 0 times favorited 7 replies Add to Favorites Watch
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Jack Lewis

576 posts in 1850 days

08-26-2017 10:48 PM

How do you calculate the complex angle in staved segmented rings? I have searched all over, found one for excel spreadsheet but no instructions of what to plug in where. Anybody have a clue? Sample of intent below.

-- "PLUMBER'S BUTT! Get over it, everybody has one"

7 replies so far

View TheDane's profile


5822 posts in 4435 days

#1 posted 08-26-2017 11:39 PM

Check this out:

Malcolm Tibbetts talks about this in his book and has a handout you can download …

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View bigJohninvegas's profile


773 posts in 2234 days

#2 posted 08-27-2017 12:03 AM

Check out woodturner pro. I was really gearing up to do segmented work and read about this.
Have been too busy working this year though, and have barely done any wood working at all this year.
So not sure how helpful it really is. Looked good.

-- John

View Tom O'Donnell's profile

Tom O'Donnell

2 posts in 2148 days

#3 posted 08-27-2017 03:05 AM

this ma be of interest for a varity of diameters

-- Getting more from my router with the aid of Template Guides Templatetom

View Jack Lewis's profile

Jack Lewis

576 posts in 1850 days

#4 posted 08-27-2017 11:23 PM

Tom O.
Your graph was exactly the direction I was headed. It works great for regular segments. However, when adding the dimensional length of the stave into the mix complicates relying on it for the accurate angle between stave sides. I have plotted the length of the stave in graph form of my design. Now, I am trying to devise a sled that takes angle and length into consideration. I can make it cut one stave angle but cutting the opposite one stumps me. I am planning on making the staves as blanks and cutting the angle in a separate operation. So I can cut all staves in a ring with one setup. Has anyone developed a sled or jig that takes the second side angle cut into consideration? I am willing to go the Incra Miter jig to assure a correct angle if necessary. This has developed into a more complex operation than seems necessary.

-- "PLUMBER'S BUTT! Get over it, everybody has one"

View Carloz's profile


1147 posts in 1364 days

#5 posted 08-28-2017 12:41 AM

You do not need freaking angles.
Draw a circle on paper with the required diameter. Divide it by the number of segments you need. Measure the distance between two dots on the circle. That is the base of your triangle. Now draw two circles with center at the each end of the base. The radius of the circle is sqrt(rr + hh) where r is the radius of your thingy and h is its imaginable height.
Where the circles intersect is the acme of your triangle. Transfer the triangle onto the wood and cut it out on the table saw.
You need to cut bevels which you can find similarly.

View Nubsnstubs's profile


1723 posts in 2502 days

#6 posted 08-28-2017 01:28 AM

Jack, I made a slideboard once for cutting angles on each edge. I made my stops on each side of the blade. As long as the second stop is high enough on the second side, the first cut will be indexed off the stop. After the first cut, just flip the stave over and position it on the opposite side of the blade and make the cut to your desired angle.

This is for straight cuts only. If you want tapered angled cuts, do the same, but set up each stop at the angle needed…. ........... Jerry (in Tucson)

-- Jerry (in Tucson)

View Dan Krager's profile

Dan Krager

4638 posts in 3006 days

#7 posted 08-28-2017 02:24 AM

Jack, I have made and used taper jigs based on a center line instead of one side and a different slope on the jig for the other. Center lining helps eliminate cumulative errors. Making a jig using two pointed metal pins arranged like centers on a lathe is nearly trivial. Draw a center line on your segment, set it in the jig so the pins fall on the center line, align the first edge with the blade (or fence) and make the first cut. Flip the segment and without making any adjustments, make the second cut. Instead of pins you could use knife edge inserts.

This is a crude sketch. Originally intended to make tapered multi-sided blanks, I’ve used it to cut double tapers on flat pieces. What doesn’t show clearly here is the miter slot rider and how it adjusts for taper, but the slots at the far left should be a strong hint. And it doesn’t show the double ended pin at the far, one end for a 1/4” hole (for strength) and the other end tapered to a point, which is quicker and suitable for light work.


-- Dan Krager, Olney IL All my life I've wanted to be someone. I see now I should have been more specific.

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