bow – plane – bow – plane -bow….will it ever end
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Hi,
I’m sure this is down to my technique, but I can’t see a way round it. I’ve planed a face and edge on a rough sawn piece of ash that is 1000mm x 160mm x 24mm and it’s all square and flat. I then proceed to cut the board into 3 equal pieces on the table saw. After cutting, the pieces I’ve just cut are bowed again, so I have to go through the whole process again – only 3 times now.
I haven’t thicknessed the boards at this point and there’s about a 1/4″ to remove to get them down to the correct thickness and I just know that the boards will be bowed again only this time I won’t have any timber left to be able to correct this problem.
Am I missing something? It seems that when you watch videos of timber prep this problem never seems to occur.
Can anyone point me in the right direction?
Thanks
Dean
I have always cut boards down before planing square, that way any movement will have hopefully happened. In any case, planing square a smaller piece is always easier than the whole, as arcs will be less pronounced when a board is cut down.
Darren.
Imagine a spider web with various strings to attach it into a corner of a room. Now cut off one string and it will change it’s shape. Cut another string, it will change again. The internal structure of wood is a bit more complex than a spider web and less flexible, but you have seen the result of cutting off fibres, which is the equivalent to cutting strings in the spider web.
Wood does relax over time and the reaction will be less dramatical, but it takes too long to wait for it. So, the best strategy is to rough cut wood to the final shape and only then start the fine work.
Planing usually has less effects than sawing, but that is, because usually, it takes of way less material.
Dieter
Wood has two properties you need to be aware of.
Stresses
MoistureMany people will cut wood roughly to size then leave in an environment close to where it will be located for a few weeks before working on it.
The thicker your wood the more problems you will have. As you but thick wood moisture content will reduce on the cut side. As the outer side will be drier it will cause the wood to curve out at the edges on the side contracting due to moisture loss. Moisture reduction happens at a rate of roughly 1″ per year.Houses are never perfectly dry. So drying wood to 100% will only cause problems when moving back to a house as things take on humidity.
The stress have been covered already.
Density of wood also hw an effect as does the way it grows
G’day Dean
I came across John Landis on YouTube and think his videos may be of some assistance to you. Here’s the link to the first in a series that has helped me in my quest to gain some level of proficiency in hand tool woodworking.
Hope it helps
Regards
Dave
Remember that perfect is the enemy of good,or something like that. My first question would be how wet was the wood when you started? If you started with green, wet, rough sawed lumber it is going to move every-time you do anything with it. If you don’t do anything with it it will move too. If it was reasonable air dry then I would consider how much bow and if that will effect your project in the long run. Some joinery can correct the bow, while some can not be cut on anything but dead flat wood. Just something to think about.
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