calling all segmented turners!

Hey, folks,

I'm battling software. I want to make a bowl with rings of 12 pieces each. That means 15 degree cuts. I figure the rings will be cut from 3/4" thick boards, 1 1/2" wide. Each ring will be an inch larger than the last. Here's my plan for the rings:

ring 1 4" disk
ring 2 5" 1 11/32 outside length of piece
ring 3 6" 1 19/32
ring 4 7" 1 7/8
ring 5 8" 2 5/32
ring 6 9" 2 13/32
ring 7 10" 2 11/16
ring 8 11" 2 12/16

First one will be in pine, so I can make my mistakes! But will the walls be too thin? What foolish mistake am I making? Woodturner pro is kind of helpful, but my mind goes completely blank when I'm confronted with any math!

Thanks,

Bill

Sorry I can't help you on this one, Bill. I definitely got the language gene at the expense of the math gene. Since you're doing it in pine, I'd say just glue it up and see what happens. If it doesn't look like there will be enough thickness, trim off the affected rings and adjust your dimensions.

I don't know why I do this to myself. It wasn't that long ago that I couldn't make a picture frame without a big gap in the miters. Now I've gotten past that, so what do I try? 12 sided rings! Geez... it's like I'm trying to make myself fail!

There's the barest hairline gap when I clamp them up. Not much, just enough for me to notice. It's gotten better since I noticed a flaw in my technique. I was pushing the miter sled through the cut, and then pulling it back. At some point, I noticed the workpiece was making a tiny sound as I pulled it back. This clearly introduced inaccuracy on the next cut. The hairline has gotten much smaller, although it's still there.

I think I'm going to have to go to the craft store and buy a big bag of large rubber bands for glueups... the band clamp works, but I only have one. My real worry is all those end grain glue faces. I guess the thing will hold together since one ring to another is long grain to long grain, but I keep reminding myself that my low speed is 600. The only thing I can visualize is dozens of pieces explosively flying all over the shop!

I've seen a bunch of sites where the turner has built a press for gluing the rings to each other. Looks like I'll have to improvise something for that too...

Thanks,

Bill

Bill, the formula I use is kind of primitive but as long as you're not trying to build a piano it comes close enough. Pi(3.14) X Diameter gives you the circumference of the rings. So on something like a 6" ring the circumference is 18.84 inches. Then if you want a 12 segment ring, divide that by 12 which is 1.57 inches and that will be the length of the long side of each segment. I use a chart similar to this to convert the inches to decimals and vice versa.
Hope that helps.

I like the press where they use a piece of threaded rod and a couple of plywood disks. Looks easy an should provide uniform clamping pressure all around the circumference.

Hi Bill, I've made a few segmented turnings lately. Looks like your on the right track. From the size of your rings, looks like it will be a straight sided bowl. You may want to think about varying the diameters to add more visual interest. My usual MO is to make, glue-up, and turn the rings smooth 3 or 4 at a time, and adjust the next ring sizes from there, based on what I think will look good. This is my most recent piece. It started out as a pretty straight forward bowl, but as you can see, it evolved It's about 12"x12" walnut. Sorry about the poor photo, dont have the light tent set up. Barry

Also, for a press to glue the rings; I apply glue,stack the rings on a flat surface and put a 50lb dumbbell (got it at a garage sale) on top for compression. works great!