I was answering a question here in the Workshop about how to straighten warped horn scales...
This little contraption is what I use for Natural scales, the dimensions on this one are 6 x 3 x 1/2 inches for each side.. but if I were to do it again I would do 7 x 3 x 1/2 inches...
The holes are 1/8 inch don't to too many as to weaken the wood...
The clamps are 2 inch
The only other thing you need is a Steam Iron, and don't worry you won't hurt it any, so the SWMBO will be OK with it :)
Set everything up as shown in the pics, and then hit both sides with steam, tighten the clamps gently, steam tighten, steam tighten, then steam a bit more... If you are using a Shot-o-Steam iron I do 3-4 blasts per... The 1/2 inch thickness of the wood and the limiting factor of the holes helps with control
Leave it alone for a FULL 24 hours and everything should be fine... Do not open it to check it, resist the urge :)
I have done Horn, Bone, and Ivory, in this contraption, there is a another thread for Celluloid in the Workshop Sticky... I have tried a heat gun but it doesn't work quite as well as the steam with the Naturals..
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Take your time and everything should go well