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Thread: How much time after milling?

  1. #1
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    How much time after milling?

    I'm new to building projects out of rough lumber. I already wish I had a bigger jointer but that's a story for another thread. My question is this. Because I basically only get shop time for a few hours in the evenings and weekends, it takes me a while to get pieces milled. It could be weeks (or longer) between when my first piece is milled and assembly. How long can I expect these pieces to stay straight? Should I get them close and then joint and plane them again right before assembly? What methods should I use to minimize warpage? I've been taught to sticker them to keep even air flow. Is that the best way to handle this? I'd be interested to hear how you weekend warriors deal with this issue.

  2. #2
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    I will be very interested in this topic. This happens to me as well and I am always concerned about the wood moving before assembly. I have had thinner pieces move on me after milling, but I am not sure how thin you can go and it not be a problem. Great question, can't wiat for the answers.
    Rise above the rest

  3. #3
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    Much (most?) of the movement/warpage will occur almost immediately when the internal stresses are changed due to the milling process.

    There may be some additional movement over a couple days - especially if the wood isn't fully dried. That's why it's often recommended that stock be allowed to acclimatize for a while in the shop before you mill it.
    Jim D.

  4. #4
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    I let my wood acclimate to the shop environment. Where I live the environment is pretty stable. In areas where temp and humidity change drastically, I hear folks let the wood acclimate in the room where the piece will eventually stand.

    I wait a couple weeks more or less depending on the state of the wood. If I know I am going to have gaps between milling and assembly (like I always do, it seems) I will mill 'close' to final size. I then let the pieces acclimate some more while I'm doing whatever it is I'm doing while I wish I was in the shop (whew, got that out of my system).

    I 'final size' the 'close sized' pieces as I get nearer assembly and glue up time. This works for me as I am a hobbyist and have a lot of other things going on in my non-work time. I have been bitten by milling to final thickness and then coming back in 2 weeks to find some warp that I cannot mill out as I am already at final size . . . do-over.
    Any sufficiently advanced technology is indistinguishable from magic.
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  5. #5
    I think you will find that most agree to acclimate your stock to the working conditions and the conditions that the shop will endure whilst you fiddle with normal tasks like going to work and family matters and an occasional sleep, between shop work exercises. This especially true to those who have garage shops and are only heated whilst working in the shop.

    I am not a believer in the term internal stress. Wood is the most layed back thing in your shop, it will lay there and allow you to do anything you wish, no complaints. Where is the stress? It is not stress but a reaction to environmental changes, when you mill wood that has been resting in a damp area and slice off a layer of wood, you expose a different moisture content than the surrounding area, this causes a reaction to correct the fiber sizes in accordance to moisture, thus a bending effect or as we call it "Warpage" No offence Jim but I have always been irked by the term "Internal Stress" I know a lot of fellows use that term but it is simply changing the surface moisture content and the natural reaction that occurs.

    So If you allow the timbers to rest in your shop at the condition you plan to use the shop for a good period of time and supply ample air circulation and provide a safe environment and a happy place there will be no stressful wood... Except for the stress you express knowing that you can't work on it until it has recooped from the stress of being moved from one happy place to another. You can try talking to it and assure it that you will only use sharp tools and be gentle, straight, & true. How you will caress it ever so lightlyy with only the finest sandpaper and complete the ensamble with the finest of finish followed by a gentle wax rubdown. I think that will relieve any stress internal or knot. It also is a good idea to leave those freshly reshapened pieces in a happy place, most prefer a good air movement and a flat level field to bask in the new surrounding. Some prefer to put on weight to make sure any nervous pieces don't raise or become stressed while you abandon them to earn income and tend to your "other" family. (Freshly milled lumber often is jealous of those who fondle them and have taken advantage of thier qualities and try to rise to the occasion, while others are just board and lay there.

  6. #6
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    Thanks for bringing this topic up Rob. I hope someone out there has a silver bullet!!

    I don't know if its internal stress or poor drying at the kiln but my experience is that the stock that was pretty straight to start with stays that way, but the stuff with cup or twist or warp wants badly to go back to that state.

    I wish I could mill and assemble the same or next day, but if I waited for that kind of window I would never get anything done.

    If I had to give some advice, it would be to go ahead and mill the well behaved stuff, but hold off on the twisty stuff until you are close to assembly and will have something mechanical to keep it straight.
    Don't believe everything you think!

  7. #7
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    I haven't found that there's a whole lot that can be done other than letting the lumber acclimate to what is hopefully a consistent environment. Last winter I bought some birch for face frames and cabinet doors, since it was cheep for out here. I ended up not using it for anything that wouldn't be screwed glued and nailed to a rigid box - never saw wood move that much when cut, I was even getting a little scared to run it through the tablesaw it was pinching so bad. Six months later, the shop humidity is up around 100%, since its in a basement that floods a bit when we get more than 1/4" of rain in half an hour, and when I was out of town there was a huge pile of poplar shavings on the floor that acted just like a big sponge and kept the water from draining through the lousy concrete floor (whole 'nother saga this building is). Anyway, now the birch is nice and stable, hardly moves at all, just like it was oak instead. I'm really hoping I have a piece left over next winter when it dries out again, as I'm curious if a slow drop in relative MC will help the stability. I'm guessing not, but still very curious.

  8. #8
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    Thanks to all for your advice. I think my strategy is going to be the following:

    1. Mill all pieces to dimensions slightly larger than the final size. Maybe 1/8". I can take my time doing this and not worry about time pressures. A pause after doing this won't hurt me. Stack pieces on level surface with stickers to encourage equal air flow.

    2. Mill all pieces to final dimensions with the expectation of cutting joinery and dry fitting within a few days. Preferably same day. If the project is too large to get this accomplished, work on a section at a time. The goal here is to have the project (or part of the project) dry-fit in some stable form to fight against any potential movement. Once the project is dry-fit, I have some time where wood movement should be minimized.

    3. Disassemble project for sanding. Can also do any necessary pre-finishing at this time. Dry-fit project again.

    4. Glue up.

    Sorry if this is all elementary to most of you but I feel that I need to be pretty methodical about this if I have any chance of success. How does this sound?

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