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Thread: How to flatten a twisted board

  1. #1
    Kerry in Calgary Guest

    Default How to flatten a twisted board

    I have a blanket-chest lid to glue up using 8/4 cherry stock. There's a small amount of twist in each of the 3 boards I have to glue-up and I have lots of thickness to work with (I'd like to end up at 1 or 1.25 inch thickness). There's about 1/4 inch of twist over a 4 ft length and the boards are 8" wide (wider than my 6" jointer). I have a 13" planer.

    I think there's a technique to flatten these boards on my planer, but thought I'd poll the experts out there first?

    How would you guys flatten these boards?

    In summary:
    8/4 cherry, 48" long, 8" wide with 1/4 inch twist - can afford to give up over 1/2 inch of thickness. Tools available: 6" jointer, 13" planer, belt sander and #4 Stanley plane.



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  3. #2
    dan in saskatoon Guest

    Default Re: How to flatten a twisted board

    that cherry is no good better give it to me lol if you had a piece of 3/4 mdf kicking around i woud make a temporary sled


  4. Default Re: How to flatten a twisted board

    I use hand planes to flatten boards.

    I have read about jigs used to securely support boards before running them through a planer. The approach is focused on preventing the board from moving under the pressure of the infeed rollers so that an even cut is removed. I believe the write up was in FWW. Never tried it; didn't like the idea of putting a sled into my planer that had boards held in place with screws.



  5. #4
    Join Date
    Feb 2006
    Location
    Montreal
    Posts
    1,682

    Default Re: How to flatten a twisted board

    Hi Kerry,

    You need to make a sled to go through you planer. It needs a stop at the back and you shim under the high points until you have no rocking . Pass it through until you get a flat enough surface then turn it and pass it normally without the sled. There is a video on theFWW site about it.

    The alternative, and I think less time consuming, method is to use a handplane to get one side to sit flat then pass it through the planer until you get the other side completely flat, turn it and get the 2 sides parrel to each other.

    Brent


  6. #5
    Join Date
    Feb 2006
    Location
    Ayr, Ontario
    Posts
    312

    Default Re: How to flatten a twisted board

    There is another method not yet mentioned, using a 6" jointer, however it is a bit more dangerous because it requires removal of the guard... just like doing a rabbet on the jointer.

    With the guard removed (being very careful!!!), flatten 6" of the board using the jointer. You will end up with a ledge on the board. Grab a flat piece of scrap the same length as your board (plywood works well) and set your board on the plywood; the ledge hangs over. Run both pieces together through your planer; this will flatten the top of your board. Once flat, flip it over and run the board through the planer.

    Anyway, just another method... keep in mind that if you try this, the cutter head is fully exposed without the guard, so be careful.


  7. #6
    Join Date
    Feb 2006
    Location
    Ottawa, ON
    Posts
    34

    Default Re: How to flatten a twisted board

    Flatten one side with handplanes. Note that you only need to get the perimeter flat ( co-planar ). Once that is done, place the flattened side down and run it through your thickness planer to flatten the other face. Then alternately thickness each side to get down to the required thickness.

    - Stephen


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  9. Default Re: How to flatten a twisted board

    Not sure what you mean by only needing to get the perimeter flat?


  10. #8
    Join Date
    Feb 2006
    Location
    Toronto, ON
    Posts
    67

    Default Re: How to flatten a twisted board

    This link describes the process that I use: http://www.woodweb.com/knowledge_bas..._a_planer.html (See the contributor's comments four from the bottom), except that I substitute veneers for the playing card shims (less slippery).



  11. #9
    David Eisan in London Guest

    Default Really, This is how...

    Bite the bullet, rip your 8" boards into 4" strips.

    The 1/4" of twist will be much less now over the length, any cupping will have almost gone away as well.

    When face jointing, make sure to get as close to the middle of the board when feeding so as to average out any twist. You should now be removing less than 1/8" over the length of the board.

    Glue up 4" strips into sub panels just large enough to go through your planer.

    Glue up sub panels for your final slab.

    This is how it is done.

    Thanks,

    David.



  12. #10
    Join Date
    Feb 2006
    Location
    Ottawa, ON
    Posts
    34

    Default Re: How to flatten a twisted board

    Only the edges need to be coplanar so that when the face is placed down on the planar bed, the board will lie flat. A little cup in the board will not matter. Once the other face is flattened in the planer, turn the board over and completely flatten the face you worked with handplanes. Now you will have two flat faces which are parallel to each other.

    - Stephen


  13. #11
    Join Date
    Feb 2006
    Location
    Montreal
    Posts
    1,682

    Default Re: Really, This is how...

    Hi David,

    I agree that that is the simplest way to do it, but, sometimes you get a board where the grain is so nice you don't want to disturb it. In that case it's nice to know other ways of solving the problem.

    Brent


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  15. #12
    David Eisan in London Guest

    Default Re: Really, This is how...

    Use a 1/16" kerf circ. saw blade to rip the boards so you can glue them back together with a very close grain match.

    Thanks,

    David.



  16. #13
    Join Date
    Feb 2006
    Location
    Montreal
    Posts
    1,682

    Default Re: Really, This is how...

    Hi David,

    Not to argue the point, but a glue line joint is a glue line joint. Your method, while proper in most cases, leaves the grain mismatched, if even slightly. The combination of the kerf and the different amounts of wood removed from the two edges to flatten the board and then again to joint it for a glue line edge will leave a noticable line in boards with lively grain patterns. There just are times when the easy way is not the best way.

    Brent


  17. #14
    Spike Guest

    Default Re: Really, This is how...

    I think the sled method is "the" method to deal with the twist, and avoid glue lines.


  18. #15

    Default Re: How to flatten a twisted board

    Thanks for that tip, Andrew. I will remember it. I have a 6" jointer and I finally have some very nice boards that are way wider than 6" that I don't want to rip down if I don't have to, when I finally get around to using them. That sounds like about the simplest method so far.


  19. #16

    Default Re: How to flatten a twisted board

    Thanks for the link, Lee. I really like the hot melt glue idea for making the shims.


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