Radius Dish Lathe turned
 

Few will see any point in this as a lathe that can swing 25" is required. Breaking down the MDF and gluing two 24" discs of 3/4" took longer than the lathe work. It only took about an hour to turn both a 15', and 28' radius dish.

Starting with a recess that could be gripped with large 9" dovetailed jaws (a faceplate arrangement could have been used instead) cutting pre calculated depth slots at different locations of the arc, then cutting away the MDF on a smooth curve using a HSS gouge. Final smoothing was sanding with a slow speed angle grinder/buffer while the dish was spinning. A light directed along the curve casts shadows on minor deviations which are further inspected simply by feel. A short straight edge is helpful and in the case of a 15' radius, the gap is about .025.

Yea, its messy, I ran a room air filter, dust collector, and wear a 3m Versaflo SCBA . Really happy with the results and have some PSA sanding discs coming.
Looking forward to sanding sides and kerfing at slow RPM with dish mounted in lathe.
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https://i.postimg.cc/YqRcjcZC/IMG-0671.jpg

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I have a friend that does them this way as well, he uses a mdf template to insert into the machined area to identify the high and low spots.

Steve

How do you like your Robust lathe?

I have no regrets getting the Robust AB model. I've had two other large lathes for comparison, a Wadkin pattern makers lathe, and the Powermatic 3520B. The Robust is well thought out and you get a feeling of finesse with it. A 3-hp Baldor motor with a VFD is some smooth quiet power. I've turned everything from violin pegs to full size djembe drums on it. Would be nice if lathes were free though, because you can easily spend as much on extras.

Steve, your friend probably hides when you show up with some round MDF :)

Using the dish under power was rewarding. This is my third guitar project. On the first, I contoured the sides with a board as described in the Cumpiano book, for the second I made some radiused beams which seemed like an improvement. I don't regret having them because they will be used to shape the braces being applied to tops and backs on a dish. Nothing new to the experienced builders here, but a big step for this beginner.

https://www.youtube.com/watch?v=qN04aMjKps4

Good to know, thanks.

How do you like your 3M Versaflow? I have an older 3M version that has pluses and minuses. I use it mostly while turning.

Your lathe-spun dish looks pretty effective.

No regrets on the Versaflo. Battery really lasts, lots of air, and the helmet is very light. Spendy but my lungs are quite valuable.