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Sequence to prep stock

This topic contains 4 replies, has 3 voices, and was last updated by  Waldo Nell 1 week, 2 days ago.

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  • #615640

    Waldo Nell
    Participant

    Hi,

    So I have a 2” thick sheet of oak that I am trying to prep into four legs each 1.5” thick. Starting with the single sheet of oak, what is the correct sequence to prep this stock? I started by flattening one face (getting rid of twist and bow), then one side and the one end. I then re-sawed it on the bandsaw to 1.55” thick. However when I did that it immediately twisted and bucked again, throwing my thickness off by 2mm.

    So do I first need to re-saw it? But then I do not have a flat face and I do not have any idea how thick to re-saw it in terms of how much bow and cup will be introduced by re-sawing it.

    Pointers?

    #616799

    Sven-Olof Jansson
    Participant

    one can make a rough layout of the pieces on the rough stock, cross cut, rip the cut pieces, and – if forced and compelled – resaw. This approach allows split reaction wood to warp before it is planed to dimension. Another advantage is that the cutting and splitting also cuts and splits the warp, resulting in less planing required.

    Sven-Olof Jansson
    London, UK; Cambridge, MA

    #616800

    Waldo Nell
    Participant

    Thanks but I am unsure how that addresses my issue. If my stock is 2″ thick, and I need to resaw it to say 1.5″, assume I already ripped and cross cut it, if I resaw it as I did in my case, it immediately introduced an additional 3mm of cup. So if I resawed it at 1.6″ (40.6mm) it would have made the stock too thin after planing (1.5″ is 38.1mm, with 3mm cup to remove – i.e. total of 6mm).

    Since I do not know how much the wood will cup after being resawed, I do not know to resaw to 1.6″ or 1.7″ or 1.8″ making it a guessing game and possibly throwing away perfectly good stock. I am not planing 0.5″ on hardwood on a large sheet if I can resaw it. So how does one solve this issue?

    #616919

    YrHenSaer
    Participant

    I think that you are discovering unpredictable internal stresses in the timber that is inherent in all dried woods to a greater or lesser extent. Wood isn’t processed cheese – it’s a dynamic material that has a spirit even when dead, dried and planed.

    It happens all the time to all pieces of wood to a greater or lesser extent. We learn to live with it, build it in, make joints that allow movement.

    The act of cutting a tree to dimensional planks, drying it (usually rapidly in a kiln) under stress – the boards are stacked with sticks and anchored by straps or the weight of other trees – means that the timber merchant has usable stock, close to a required dimension.
    When this stuff is transported elsewhere, maybe to different climatic conditions, it takes time to acclimatise. That wood contains internal stresses; thicker pieces are more prone to this than thinner boards.

    The act of re-sawing a thicker piece, in your case about 2 inches, releases internal stresses in the wood fibres, and exposes new wood faces that may be at a different moisture content. The immediate result is movement, as you have found out. Often, even ‘stable’ wood, will move or ‘cup’ overnight.

    What to do with your large piece?

    Plan ‘A’: If the distortion is severe, use the experience to predict what happens to other pieces from the same plank or tree that you have and discard it for a better-behaved plank.

    Plan ‘B’: 1 ½ inches is not particularly thick for legs. However, you now know that your board is prone to internal stress. Personally, I’d cut the pieces oversize, allow it to sit for a few days… a week or two, then gradually plane down the unwanted twisted portions. Do it gradually because you may release more internal tensions until you get pieces at the sizes you need. Cut five legs and use the best four.
    It’s not a precise art…. If it doesn’t work…. Back to Plan ‘A’.

    Good luck, we’ve all had this happen. It’s the start of an Odds-and-Sods stack of discarded wood that comes in useful later.

    #617007

    Waldo Nell
    Participant

    Thanks, that was very helpful. I am making the eco bin project so that is why the “legs” or support beams are 1.5″ thick.

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