# Stave turning how do you figure it out????



## ArlinEastman (May 22, 2011)

I would love to figure out how to do stave turning and teach the vets when I get good at it.

I know the angle = how many staves I want / 360 all stuff, but….....

If I want say a bowl with a lid how wide at the top do I need to make the stave if say I want a 8" bowl???

I know if I want 12 staves it will be a 15* cut but what is the taper width if I want it at say 30* or 45* or any thing else??

I also know it depends on how high I make the staves but it all comes out the same no matter if it is 3" tall to 20" tall the formula is still the same. I just need to understand how to figure it out so if I want a 4" bowl or 20" bowl I can do it every time.

Thanks


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## drsurfrat (Aug 17, 2020)

I think I know what you mean.

a/alpha = angle of your staves
R = *outside* radius of your bowl
c = chord length
h = height of the chord section (calculated, NOT your bowl thickness)










You want the full length of the excess angle that will br turned down later. It would be the chord length with additional length:










The drawings have larger than typical angle, but the math should work no matter what. And remember, most calculators deal in radians instead of degrees.

Even if this is exactly correct, I would still make a paper templates with my grade school compass and ruler.


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## hairy (Sep 23, 2008)

You might want to binge watch some youtube, there's a lot there.

I've often wondered if those birds mouth router bits would get me a good stave blank to put on the lathe. You can see them on youtube, this guy has a lot.

https://www.youtube.com/user/davidhenry32

https://www.amazon.com/MLCS-8357-2-Inch-Multi-Sided-3-Piece/dp/B000H8UOM4


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## Jim Jakosh (Nov 24, 2009)

Hi Arlin. as far as the taper goes with staves, what I do is calculate the circumference at the top and at the bottom. Divide the number of staves into each circumference to get each width. Then make tapered staves to those dimensions at the top and the bottom.

I glue scrap pieces on the ends to turn them round and put a spigot on the top piece so I can hold it by that to turn the bottom and make a relief to glue in the permanent bottom. Then, holding by the bottom, I finish turning the inside.

Cheers, Jim


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## ArlinEastman (May 22, 2011)

Mike

Thanks but I just do not remember my Trig and Calc from the days of being a machinist and with my brain damage I forgot to much.

Hairy

I have been eying those bits for several years thinking the same thing as you and it might add appeal. I also forgot about bring it up on YouTube.

Jim

I will try that out as well in the next week or so.

Thanks guys


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## Loren (May 30, 2008)

> I know if I want 12 staves it will be a 15* cut but what is the taper width if I want it at say 30* or 45* or any thing else??


Making a cone? With mild tapers and more staves you can fudge it but with steep tapers trigonometry will get you the answer you need. I used to know how to do it. With barrels or conga drums you can more or less ignore the trig but with something like a short and wide birthday hat the angles change and move more towards right angles with the taper coming from the tapering jig with the blade set at a shallower bevel angle.

An idea that might help is to take an umbrella and imagine how opening it would flatten out the beveled edges if the umbrella shape were wood. If it were flattened out entirely the bevels would be 90 degrees. You can even put craft rings on the umbrella to see what happens at different points in opening.

I used to make conga drums and would use steel rings pounded down on them to close the joints. There are other ways to do it, but rings worked the best for me on a taper. The rings would bit into the wood a bit and that sort of kept them from slipping off as I recall. Some forms I made required other tactics for glue up.


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## LeeRoyMan (Feb 23, 2019)

I would draw it in SU

Your 15 degree bevel changes with the angle/splay of the sides.
Sketchup eliminates the math.

Here is a bowl: 6" high, 8" at the top. 4" at the bottom. the bevel on the sides of each stave is 14.3 deg.
After drawing it, I can just measure the stave at the top and bottom.


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## drsurfrat (Aug 17, 2020)

Would a chart help?

This gives the widest width of a stave necessary to make a segment column/bowl/cylinder of different diameters. Also includes saw cut angle. Yes, the 4-sided version is impractical but it checks my math.










- illegible to my eyes, here is a link to a jpg file

https://www.dropbox.com/s/14pn1sd0g1djv9s/segmented%20bowl%20dims.jpg?dl=0

from above, the dimension in the chart are for the two outermost points at the end of the trapezoid that will be the stave.


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