Fixing warped end grain cutting boards.

[Zac wingert]

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Made 10 end grain cutting boards in two batches. In the second batch, three out of five severely warped. The above photo is a mini one I made out of the scraps that shows the worst of it. The full size ones are not as bad but within the unacceptable mistake range.
Two inquiries:

1. How to prevent this from happening again. My first thought is that one or more of the species were not dry enough. To this end, I think I know what I did wrong. When I bought the rough sawn. Most of it was wrapped in plastic because it was raining real hard, but the two smallest pieces, wenge and Paduak, I put in the cab of my truck. On the way home we picked up the kids and I threw those two boards in the truck bed, in the rain. It was a 5 to 10 minutes drive home, in the rain. It dried of the boards when I got home and left them in the garage, the ones in the plastic were dry. I live in Hawaii and I really don’t worry too much about wood movement due to the weather.

It sat sat for a day, then I jointed and planned the boards. The remaining steps of making end grain cutting boards were done over the course of about 10 days after I came home from work.

They warped in a single day. I did the sanding with a belt sander first, next day ROS 120, next day ROS 220, and next day ROS 320. I know they were not warped at this point, but the next day when I came home from worked they just got crazy. They are cupped, and rather uniformly.

Its eastern maple, walnut, Purple Heart, zebrawood, wenge, and paduak.

2. How do I fix this? I have only a six inch jointer. Not gonna help. Make a planer sled? I have a dewalt 735. Toss the three?

The ones that turned ok, I am happy with. They are all Christmas present and it seems I will need more than 10..

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[Roger Marty]

My cutting boards are often very slightly uneven :-(

I don't think you want to send them through the planer. The end-grain can actually wreck your planer

[johnny means]

My first guess is that you left them sitting with one face exposed. The end grain on the exposed face lost moisture much faster than the bottom face. Stand them on edge for a while and they may very well flatten out once they hit equilibrium.

[Brian Nguyen]

I've had this happen to me before, just lean them up for a few days and see if the board flatten out by itself.
For end grains, I suggest putting feet on your boards. Otherwise, the recipients will likely have similar warping and even the board cracking if they're not careful at the sink. Feet will raise the board up above any standing water and allows for even trying on all sides.

[Nick Lazz]

This has happened to me as well. There's two solutions... sand, sand, sand and sand some more or add feet to the bottom of the board. I put feet on all of my boards now, I just think theyre better that way.

[Phil Mueller]

My end grain cutting board is constantly moving out of flat. It doesn’t have feet, stays on the counter, and often gets a bit of moisture underneath. As a result it cups. I simply turn it over and use that side for awhile until it slightly cups...then turn it over again. It gets oiled about every two months. It’s been doing this for about 10 years now with no sign of failure.

My point of this is to suggest you set the convex side on something damp and see if it straightens out.

[Jim Barstow]

Putting feet on means you can't use both sides. (I put a juice groove on only one side so you can use the other for chopping.)

When I have concerns about warping, I do the minimum amount of milling to make the board flat then let the wood sit for at least several days. If it is still flat, I mill to final dimensions. If not, I mill flat again and let it sit again. I've had instances where the board never stabilized but better to know that then use it and have it warp in place.

[Andrew Hughes]

I don’t think there’s any fixing a end grain board that has that much warp. Ask yourself how do I make a end grain cutting board that will not warp badly.
My experience has been the wider they get the thicker they need to be. My 12x12 are minimum 2 inches but I don’t mix a lot of other species. That’s just asking for trouble
Keep at it let us know what you find.

[Zac wingert]

Thanks for all the help. I put them on their sides today, and they moved partially to flat. After reading all the replies I am not too worried any longer. They moved maybe halfway back, haha ‘I’ll deal with t.

I do put rubber feet, but I wasn’t to that point in the process yet. I had been adding them after the finish.

[Ron Citerone]

I think letting the wood get rained on was a mistake, as was not letting the wood acclimate longer. I've had some (not always) bad episodes with wood that has not acclimated and now I don't use wood until it has been sitting in my attached garage for a month...............get the wood for the next project while you are working on the present project. And all cutting boards need feet IMHO. Eliminate some of the variables. Store wood with some thin stickers between them so air exposure is equal. My 2 pennies.

Also, end grain boards by the process get a lot of added moisture from all the gluing. I would let them dry/equalize a long time after gluing before moving on to the next step. After gluing up, I let them sit for a week while I work on other stuff............some will say it's not needed. I have learned to glue up any board or panel as much in advance as possible..............it has helped my woodworking a lot. The way I manage my glue ups is a priority. It takes a longer time horizon in planning, but I always think ahead several steps while I am working on one part so I never don't have something to do when I get shop time. RC