I cut and surfaced 3 thin hardwood blanks this afternoon to carve the male plugs for inlays. The plan was to do the glue-in tomorrow.
I have just gone down into the basement (its mid-evening) where my CNC is to check on some other WIP, and to my disgust, all the blanks have warped and are now good for firewood !
So I guess the best practice is to cut and use the blanks immediately after preparation? Who would have guessed they could bend so much in just 4 or so hours !
Wood can warp quickly, especially when it’s thin! I’ve been known to use a few strategies to get around that.
If you can segment the inlay that warped, it minimizes how much warp you have to deal with.
Build a screw press for your glue ups to both flatten the warp out and hold things in place while the glue dries.
Place thin carves in a plastic bag , squeeze the air out, and seal it. This will limit moisture mitigation.
The process of removing material changes the stress in the wood and really lends itself to making the wood want to move. It’s hard to stop warping and cupping but hopefully these tips will help you work through it and minimize the impact.
@CncJim makes some good points. Not sure how bad your boards are warped or if your doing a v-carve or traditional inlay but I have done some v-carve inlays with boards that were not flat. If you can get it to lay flat with clamps for v-carving then when you put it in the screw press for glue drying if may come out all right.
I don’t have a screw press per se but I used some MDF on top and bottom and clamped it with 6 clamps. This was on a 6"x12" cribbage board. Your mileage may vary. Another trick I tried that worked was with a v-carve inlay that came out to thin. If you have an accurate way to reposition you work piece and the inlay comes out bad you can run the v-carve on the pocket piece to clean out the plug. You need a really accurate way to position the stock for this to work. I used four 6mm rods that go into holes in my spoil board and the holes I milled into the work piece so I can take the work on and off the mill accurately.
The cribbage board I posted here failed the first inlay but I was able to save the walnut and only lost the thin maple on the first try.
Thanks Michael and Jim for those helpful responses!
@GregM Just a quick add to the other excellent advice; when you are surfacing wood to final thickness, whether using the Mill or a planer, be sure to take wood off both surfaces of the material. You want to even the stresses on both sides as much as possible.
Finally, use kiln dried lumber rather than air dried lumber if you can.
Thanks ! Excellent points and I am doing both of those.
Of the pieces I prepared (purple heart, cumeru and walnut) it seemed that the cumeru was unaffected, only 1 out of 3 purple heart warped…but all walnut was a write-off.
I had some cupped material from sitting the garage without air circulation underneath, causing the top to dry out faster than the bottom. I put the board near my IR heater to help dry it out enough to flatten it.
Then I quickly machined it, and filled it with epoxy to keep it from warping again. 