Open any book on segmented turning and you’re likely to see at least one chapter filled with numbers, angles, and formulas. But you don’t have to be a mathematician to calculate the angles, lengths, widths and depths of the building blocks that make up a segmented glue-up. Some simple multiplication or division is all that’s needed. In this clip, I’m pleased to present segmented woodturner, Don Leman, who demonstrates the easy way to figure out how to calculate the dimensions of each individual segment, no matter how complicated your project may be. It all comes down to some very simple rules. It’s easier than you think. (4.5 Minute Video)
A number of you have asked for the formula that Don uses in my video on him. We’ll, there’s good news. He has put together a handout which includes the formula for calculating the segment dimensions. It’s a pdf document that you can download from his site at:
Good stuff! Thanks!
Wow, this is interesting! I love it!
This is great. I have spent hours watching how-tos but Don’s is the most clear and understandable I have seen. I am now looking for more of his demos.
Don, I started segmented turning a couple of months ago. Your video lessons are a Godsend, and an inspiration. Thanks.
Were on the Internet can you get a chart for calculating segmented bowls?
Keith’s Note: I’d refer you to the first comment above. A link is there. Good luck.
This calculation doesn’t give any allowance for turning the blank round.
Keith’s Note: Don has had tremendous success with this approach, so I’m not quite sure in which way it is deficient. Maybe you can elaborate on how you like to calculate the cuts as it might help others..
Is that a Shop Smith table saw that Don Leman is using? It sure looks like it. I have often wondered what level of precision you could achieve with a universal machine such as that, and if Mr.Leman is able to cut accurate segments with it, I think that clears up any question I may have had.
I do wish i could find one at a reasonable price with some attachments. Really an awesome machine, and very neat to look at as well.
Keith’s Note: It is indeed. Don is a clever guy and he’s combined the Shopsmith with a Incra MITER5000 Miter 5000 Table Saw Miter Gauge. The combination allows him to do some of the most precise woodworking one can imagine.
@ Keith474.. Check your local Craigslist and /or want ads.. I see older Shop Smiths going for about $300.00 to $500.00 all the time.
He gave the diameter as 5.5 inches. The final diameter has to be smaller, since you are going to lose some wood in turning it round.
I have an Excel file that does these calculations. It tells me how thick the piece has to be. I would plug in 5.6 inches so that I would be able to turn it down to 5.5 inches. This would give a length of 1.501 inches. For a finished thickness of about .3 inches the blank should be about .4576 inches thick.
Keith’s Note: Thanks Terry for following up with more details on your approach.
Tanks for the info.
Cut a 12 piece segmented ring on my miter saw. Did the math 360 degrees divided by 12 equals 30, divide that by 2 that gives me 15 degree cut on each side. When I put the pieces together I have a gap 1/4 to 3/8 inch. What happened.
Keith’s Note: I’m not sure. Sorry.
How does the calculation work for a tall tapered vessel using vertical staves ?
Keith’s Note: That’s a good question.
Hi Dave, the calculation is correct. Maybe your 15°-setup is not correct. This must be very correct. A faulty set-up will be multiplied by 12 !!!
Dave, could it be the saw blades kerf that’s messing you up? Try measuring the space at the end and cutting it into 12’s then adding that much extra to your pieces or basically, add the width of your saw blade to each cut. It could be the problem. Are you cutting the 15 degree on each piece or are you cutting it on one long piece then cutting that to length?