Large bowls/platters, 10% rule still apply?

[alex grams]

99% of my turning is bowls in the <14" diameter range, but I cut up some soft maple today that I want to make some 24" diameter platters from (roughly about 8-9" in height). Does the 10% rule still apply, or do most people max out at about 1-1.5" of thickness? My normal drying method is DNA soak, shrink wrap last 1-2 inches of the rim, then bag the bowls for a few weeks, and then take the plastic off, put them back in the bag for a month or two, then air dry. I can't do DNA with the 24" bowl, so would most people recommend the ~1" thickness, seal/wrap the end grain and use a bag?

Thanks in advance.

[Roger Chandler]

Alex.........I would think that in most cases leaving 1" thickness on a platter would be sufficient to re-true after drying, but with a 24" platter, just to be on the safe side, I would rough to 1.5" just to make sure.........just my thinking on it.

[Bob Bergstrom]

Soft maple is relatively stabile but being 24" across warpage may be a concern. I used to sell lazy Susan's over 20" from glued up kiln oak and still had warpage problems. A platter that is the same thickness is better. Take material out inside the rim will increase the chances of warp. You may have to turn it three time to let it acclimate to the environment.

[Reed Gray]

Especially for platter stock, cutting the blank can make a huge difference. If you are taking a quarter sawn blank, then it will stay pretty stable, so a 24 inch wide one shouldn't move too much. If you are taking off a slab much past the center quarter sawn section, then cupping and bowing can be huge. Wood species can make a big difference, and so can the season you harvest it in.

robo hippy

[Thomas Canfield]

My biggest has been just under 20" (Powermatic 3520B) and about 9" deep and the 10% worked for Oak, Sweet Gum, Pine, and Bradford Pear. The warpage and going oval seem to require the 10% and that also leaves enough mass to prevent flexing when you true up the rough turn piece and then work the thickness down in stages. I have had to return the outside twice due to movement after truing up the inside and the wall thickness would have about 1/4" variation when stress was relieved on the Sweet Gum material, before being able to turn to thickness. I like to have a thicker section or wide rim (say 3/4-1") and then thinner wall (about 1/4 -3/8"") below on the larger pieces to have some rim strength and still have a reasonable weight piece.

[Dennis Ford]

Some wood will be OK with less than 10%, I would think that most soft maple would be in that category. Be careful when you turn rough-outs thinner because the thinner you leave it; the more it will warp. Shape is also a factor; a salad bowl shape is more likely to have excessive warp than a platter.

[Pat Scott]

...but I cut up some soft maple today that I want to make some 24" diameter platters from (roughly about 8-9" in height).

I was confused by this sentence because the way you wrote it says you want to make 24" diameter platters that are 8"-9" in height?

For platters I chainsaw 2" thick slabs and let them dry like that. I used to rough turn them, but the time involved to do that usually ended up being a waste of time. First off you're committing yourself to a shape, and you're committing yourself to which side is up. I've had blanks that warped so much that in order to true it up I ended up with a dinner plate instead of a platter. Or a crack would happen and ruin my roughout. I've found that if I have a 2" slab to work with, I have enough mass to true it up, shape it how I feel, and get rid of cracks. As Reed says, quartersawn is the key. Only take platter stock from the middle, any further out and it can warp like a potato chip.

The best plate and platter stock comes from the log as shown in the first picture. In order to get a 24" blank from pic 1, you'd have to have a HUGE tree (like 50" across). So to get big platters, pic #2 is your next best option. If cutting like in pic 2, try and stay away from the pith 1/2" to 1". If too close, during the drying process you'll likely get a crack. Avoid the temptation to try and get two platter blanks next to each other as in pic 3 - even if it is a big log. You're getting too far from the pith, the growth rings are getting flatter, and you'll get more warping.

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[daryl moses]

Great tips Pat, thanks for sharing. I will keep them in mind next time I cut some platter blanks.