Rough turning a platter?

[Eric Gourieux]

I have a 12" x 3-4" wet cherry blank with some nice feather. I've rough turned (and wet turned) hundreds of bowls and HF's, but I've only turned platters from dry blanks. Do you rough turn your platters? If so, do you follow the 10% rule? Use DNA? Seal both sides? Bag? Thanks for your help.

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[Dale Miner]

The ten percent rule will usually work, but in general, it is not needed to leave the piece quite that thick. Some analysis of the grain in the piece taking into account how much tangential shrinkage is expected will help in determing how thick.thin to leave the roughout. The shape of the rough out will also have an effect. If the platter will have a bowl section, then it must be left thick enough to allow for the radial shrinkage to occur and leave enough thickness for the bowl to finish out with the desired wall thickness. If the blank comes from near the center of the tree and is essentially quater sawn, then there will be little tangential shrinkage during drying and the piece will stay relatively flat but will have radial shrinkage and become out of round. If the blank comes from near the outer portion of the tree, then there will be more tangential shrinkage during drying, the rim will stay less flat, and there will be slightly less out of round shrinkage. Blanks cut through the feather of a crotch usually stay fairly flat.

I usually leave 18" platter rough outs about 1.25" to 1.5" thick depending on the above factors. Leaving thinner helps reduce the risk of cracking and speeds up drying but increases the chance that warping during drying will prevent cleaning up during the second turning.

As to drying method: I just bag my roughouts and let them dry for a month or two and then remove from the bag. After a year or so they are dry. Some others may be able to offer advice of accelerating drying. Blanks containg crotch feather need to be dried slowly, as the grain in the feather is exposed as end grain and dries faster than the surrounding wood. Drying too fast can cause checking in the feather.

[Robert Henrickson]

I recently was faced with just this question -- damp cherry and potentially great feather. I simply turned it to finish and let it do what it would -- ended up somewhat distorted, so I just put it on a display stand. I'm not sure how it would have behaved if rough-turned and returned -- there was already some checking in the log, so I decided on "once and done". After turning and sanding, sealed with it with a couple coats of dilute lacquer and left it for a couple months before final finishing coats. As for DNA -- 15" diameter (in my case) would have required a big container, and I haven't used DNA in any event.
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[Reed Gray]

You want green platter blanks to have the center of the tree on the bottom. When drying, the edges will warp up/away from the center, so you get some cupping. If you have the bottom towards the outside of the bowl, the edges will warp down, and every thing in the center of the bowl will roll off.

robo hippy

[Bernie Weishapl]

I generally use the 10% rule also on platters just like bowls. Works well for me.

[Eric Gourieux]

Thanks, guys for your input. It's all very helpful, since I don't have much experience with platters. I think I'll get it turned to shape and see what I have. I may be forced to turn it too thin to rough out, dry and re-turn, because of the shape of the branches on the bottom of the blank. This piece isn't the prime, center, feathered piece from this crotch. I left it for my friend who is a fellow turner and who gave this piece to me. It was his cherry tree that I help cut into blanks. I'll post the final piece sooner or later.

[Eric Holmquist]

I've green turned several platters, and usually make them a bit under the 10% rule top to bottom, but give them a bit over 10% margin for the rim width.

I make them in pairs and clamp them facing each other with the grain aligned. They go oval, but stay flat because the two platters apply opposing force to one another.

My clamp is 2 pieces of 3/4" plywood with bolts in each corner, and a hole in the middle to accommodate a tenon on the back of the platter.

[Eric Gourieux]

Thanks, Eric. Do you keep them clamped together until dry?

[Eric Holmquist]

Yes, I keep them clamped until dry.

[Pat Scott]

I used to rough turn platters but don't anymore. All I do now is cut a 2-1/2" thick blank, mount it between centers and clean up both sides so they are fairly smooth. A smooth surface is easier to apply Anchorseal to than a rough chainsawn surface, and I also want to make sure I've completely removed the pith and a little more. I'll also clean up the edge so it's smooth too. You don't have to get rid of 100% of the chainsaw marks, it's OK to leave a little. I aim for a 1-3/4" to 2" thick blank when I'm done smoothing it. Yes it might take a couple years to air dry a 2" thick piece, but I have so many blanks drying that it's not a problem waiting.

Some might argue that 2" is too thick, but this way I'm not limiting my design options. If I roughed it out to 1.5", by the time it warps and I clean it up, I might end up with 1" to 1-1/4". This might not be thick enough to make as deep of platter as I want, or might not be enough thickness to form a nice ogee on the bottom or whatever other shape I want. Rough it out to 2", let it dry, true it up, and you end up with 1.5" to make whatever you want.

Plates are shallower than platters so I rough them to 1.5", and end up with 1" finished.

The reason I stopped roughing out blanks is I had a few that I rough turned too thin, and they warped so much that they looked like a potato chip. By the time I trued them up and got rid of the warp I went from a 18" platter to a 12" plate. Also by rough turning you are committed to which side is the top and which is the bottom. Leaving it a solid slab gives me the option to flip it around if I want.

The best platter stock is quarter sawn, starting from the pith and going out. This means if you want a 16" platter you need to find a tree that's 32"+ diameter. The next best is a slice along either side of the pith. Don't try and take a platter blank any farther away than this as it warps too much.

[Jon Nuckles]

I have followed the 10% rule and usually come out all right. Just last week, however, I had to turn a 16" platter roughout into a 9" plate because it warped so much when drying. It was a crotch piece, which may have had an effect on the warping. It had beautiful feather and I hated to lose so much of it. I may try Eric H.'s clamping method next time I get a particularly good piece for a platter.

[Thomas Canfield]

The picture and feather looks like it is fairly close to the pith area, and there will be some wild distortion around the perimiter on that side and also cupping and possible splitting at the center of the feather. Are you going to turn round platter or leave the wings. I don't have much experience with DNA, but you can use a bag and get by with less liquid than a container. Cherry has always moved quite a bit for me, and it looks like this section is going to move. Turn thin and DNA might be the best to end up with something close to what you turn. Turned thick, it might warp more than you can staighten up but 10% would be my minimum guess for rough turn.

[Roy Turbett]

Anybody ever use something similar to an old wood tennis racket frame? If I remember right they had four wing nuts with springs that held the frame open so you could slip the racket in.