Getting a plate truly flat

[Bob Hodge]

I need a technique that I am obviously lacking.  I'm working on some 10-12 inch wide plates and bowls where the bottom of the inside should be flat, truly flat.  Past eyeballing with a ruler across the plate or inside of the bowl, and using a small squared scraper, I put on some mineral spirits to see how the sanding works before putting on a real finish. Looks pretty good to me, but  I still seem to get waves that show up when putting a finish on with any kind of shine.  

My best shot is to just sand the daylights out of the piece with a piece of sandpaper on a wood block to smooth out any waves that circle the center.  Is there a faster, simpler, better way?   

 

Thanks, as always.

[Gerald]

One question Is the wood dry? If not let it dry before trying to get a flat bottom.

 

Second you said small scraper which I interpret as 1/2 inch or less. So try a wider scraper, flat nose or straight. To test for flat the old flatwork technique is to scribble with pencil over the area to make flat. Then try sanding with a block and when all pencil lines are gone will be flat. If you sand with the mandrels we usually use there is some flex in the pads and can therefore maybe leave waves in a flat surface.

[Bob Hodge]

I'm sorry, but this surely can't work. 

 

It's too simple.  

 

Yes, of course.

 

Thanks

[Masonsailor]

Another method I use is a 4” scraper from HD. They have replaceable blades that are very sharp. Just a light touch and it will flatten things out nicely. 
Paul

[Bob Hodge]

Yes, so simple. I have been eyeballing "flatness", even putting a card scraper across to see very little waviness across the plate.  Only when putting on a finish with some shine did the circular "waves" of uneveness show up.

 

Drawing pencil lines across the piece and sanding with my random orbital sander until the lines were gone worked just fine. I then go with the grain with sandpaper and/or card scraper to get the smoothness needed.  

 

I was kind of hoping you would recommend a new tool....