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After shock warping

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kaashif

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Hi i have recently started wood working and have a cnc set up. yesterday I flattened some sycamore and carved some designs. I brought the peice in and this morning the slab has developed developed twist. I machined it flat and the two offcuts after being machined which were in the workshop are still flat but the main peice is twisted considerably

any suggestion how I should try to flatten it and also why the other off cuts remained flat?
 

Daniel2

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Is the atmosphere in the house warmer and drier than your workshop ?
 

D_W

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differential drying in the wood causes movement (as in, if bits of wood next to other bits shrink more than they do in other areas on a board, they'll pull the board toward the shrink or crack if that's what it takes to get relief).

The offcuts probably just don't have enough surface area or as unfavorable of a grain orientation.

There are ways to flatten boards, but a better idea in the future is to acquire wood, observe it and use the stuff that stays flat. The stuff that doesn't, let it finish moving, then dimension it to flat and then check again. At some point, most wood stops moving. You can end up with residual stress remaining in wood, but stress itself is far better than stress plus movement in the first season or so.

Other strategy here is if you're making things that will end up indoors, let the stock acclimate indoors and then take it to your shop and work it.
 

kaashif

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differential drying in the wood causes movement (as in, if bits of wood next to other bits shrink more than they do in other areas on a board, they'll pull the board toward the shrink or crack if that's what it takes to get relief).

The offcuts probably just don't have enough surface area or as unfavorable of a grain orientation.

There are ways to flatten boards, but a better idea in the future is to acquire wood, observe it and use the stuff that stays flat. The stuff that doesn't, let it finish moving, then dimension it to flat and then check again. At some point, most wood stops moving. You can end up with residual stress remaining in wood, but stress itself is far better than stress plus movement in the first season or so.

Other strategy here is if you're making things that will end up indoors, let the stock acclimate indoors and then take it to your shop and work it.
okay thank you I will have to keep all of the
in mind...
 

baldkev

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How thick is it on average? And how big in size?
 

kaashif

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boars was about 1.25inch thick it was flattening to about 1 inch size is about A3 sheet

did spray one side with water and weighted it down overnight does seem okay but I'm.worried it will warp again once given to customer. can I seal it or use oil/wax to stabilise it?
 

baldkev

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I think about the only thing that would seal it enough to keep the moisture levels stable would be epoxy resin? Is that an option? I recently made a box and the lid warped when i brought it in the house, but after a week or so, it had returned to being flat! Often once its moved it stays that way.

The wood will reach an equilibrium with the moisture levels of its surroundings, but maybe clamp it flat and keep it in the customers house for a week clamped down? Not ideal, but maybe safest to try to keep it stable?
 
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