Trays - flat bottoms

[Scott Morgan]

Hi everyone. I've just started to try and turn some flat bottom trays/bowls. I swear that I saw an article in the American Woodturner about turning flat bottom platters or trays, but I can't seem to find it. Am I imagining things, does anyone know if one was published. I tried searching but noting came up. Anyways I'm looking for some hits/suggestions/tricks. I've included a picture of a small one I just did.

 

[Bill Boehme]

A perfectly flat bottom might be practically impossible because the seasonal changes in humidity will cause the wood to change shape slightly. If I am making a platter I go for a very slight barely noticeable dish shape. This way you can eliminate the ripples-in-the-pond effect of a flat bottom. Personally I wouldn't use vertical sides for two reasons:

• There's a greater chance over time that seasonal movement will cause the side to develop a crack
• The vertical sidewall interferes with tool usage to work on the bottom whether you want a flat or curved bottom

I don't remember an article on this subject, but then I don't remember a lot of stuff since becoming a geezer.

 

[john lucas]

The simplest way would be to use a paper joint with a glue block. If you already have a flat bottom piece of wood just glue the glue block to the bottom with a piece of paper in between. When your finished turning just push a knife through the joint and pop it off. The paper and glue can be cleaned off with White vinegar or you can scraper and sand it off.
to turn a flat bottom you could turn the plate and then reverse turn the bottom using a jam chuck or best of all a vacuum chuck.

 

[Dennis J Gooding]

If you use a vacuum chuck to reverse, use minimum vacuum. Otherwise, spring-back after vacuum is released may lead to a rocking bowl.

 

[Scott Morgan]

Thanks for the replies so far, just to clarify, when I say flat bottom I referring to the inside, not to the bottom that is sitting on the table, for that I know it needs to be dished out slightly.

Dennis thanks for the comment on min vacuum pressure. I just had that happen on a one that I had turned a bit thinner then planned. Easily fixed with some sand paper laid down on my table saw.