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Question on diameter in woodturner pro and segment pro

Sheldon Fielder

PRO Member
So I was wondering if anyone has figured out the maximum diameter you can design a bowl for mounting on a 12” swing lathe. I’m assuming the diameter given on woodturner pro is the finished diameter? I haven’t measured it out yet myself just curious if anyone has so you know what is the biggest diameter you can go when designing. I also assume it will vary with the number of segments per ring but just curious what others go for diameter for a 12” lathe. I also could be wrong in this matter if so let me know. I just don’t want to go threw with all the cuts just to find out it won’t mount on my lathe. Thanks
 
Hi Sheldon.
- If you have a 12" swing lathe , then the very maximum diameter would be just shy of 24" diameter. To be safe a 23" diameter bowl would be about the largest you could mount.

- The diameter calculated (shown) in WTP or SP is the ring diameter when rounded. So yes, it is the finished ring.
- I have never tested the design more than what my lathe will swing. Just for grins I put in a 20' (240") and it did the calculations correctly.
I have never gone over 120 segments per ring. Just tried 400 segments per ring and it calculated properly.
- The number of segments in a ring has nothing to the diameter of the ring. Number of segments in a ring only changes the segment edge length, not the diameter of the ring.
- The circumference of a circle is the Diameter x Pi (3.1416)
- Circumference divided by number of segments equals segment length.
- Segment Angle = 360 / number of segments / 2 (because the angle is cut on each end). A simpler way to say it is Segment Angle = 180 / number of segments.
ring 1.jpg
 
Sorry should have said 6” swing so max of 12” diameter. So now I know that the max diameter they give on them is the finished but with that being said if I was to put a 12” diameter bowl into SP then I wouldn’t be able to turn on the lathe as the corners would hit first. I’m having a hard time explaining but I could just go for a trial run and see. Thanks for the answer tho saved me from doing a bunch of work.
 
Sorry should have said 6” swing so max of 12” diameter. So now I know that the max diameter they give on them is the finished but with that being said if I was to put a 12” diameter bowl into SP then I wouldn’t be able to turn on the lathe as the corners would hit first. I’m having a hard time explaining but I could just go for a trial run and see. Thanks for the answer tho saved me from doing a bunch of work.
One of things I like about the older program (WoodTurnerPro) is how easy it is to
- increase the outside and inside diameter.
I generally add a 1/8 to 1/4" outside diameter to the design and turn down to the final diameter.

You might get away with a 12" diameter bowl on your lathe.
If you have a disk sander it is pretty easy to round down the corners first. Then mount the vessel on the lathe.
 
You can always knock the corners off with a bandsaw as well I to have a 12 inch lathe 6 inch swing
 
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