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Thread: Must I laminate both sides of everything to avoid warping?

  1. #1
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    Must I laminate both sides of everything to avoid warping?

    I am building a router table to place in my table saw wing. My intent is:


    1. Build an oak frame that is roughly 2" x 7/8".
    2. Cut the top from 1" MDF
    3. Laminate the MDF bottom.
    4. Attach the top into the frame so that the top is flush with the frame.
    5. Laminate the top and the frame.

    Two questions:

    Question 1: If I do the steps above, then the top of the frame is laminated and the bottom is not, is that a problem? I assume not.

    Question 2: If the top is flush with the frame, do I need to laminate the MDF top and frame? I intended to do this to make sure that the wood never caught on the frame lip. It does make it marginally more difficult to mount the table.

  2. #2
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    Can't say for sure, but there's likely quite a difference in rate of expansion/contraction with temperature and humidity between the laminate and the MDF - and despite the pretty thick MDF laminate can be pretty strong stuff. My personal instinct would be to play safe and make sure that the construction of the top and the bottom is the same. i.e. of the same materials, same thicknesses, same exposure to the atmosphere and both laminated...

  3. #3
    The oak frame..... is it gonna be the 7/8" edge flush with the top? Or is it gonna be the 2" face flush with the top? I'd say you're fine with the 7/8" edge flush with the top even though I would rather rabbet the oak so that the oak edge doesn't appear as wide. And just what is this laminate? Formica or wood/ something else? If it's formica or something airtight, you might run the risk of the edges of plastic laminate delaminating in the future if you lamininate on the 2" face of the oak. The point of all this is that I'm concern of the movement of the wood in humidity related situations.

  4. #4
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    Andrew,

    It's always best practice to laminate both sides of a panel with similar material. Not doing so sometimes works out, but sometimes it leads to unhappiness down the line.

  5. #5
    You need to laminate both sides to prevent warping. P-lam and MDF are very close to the same as far as enviormental change movement. Remember, both are wood products. Problem is that moisture/humidity will enter the raw MDF side a lot quicker than the laminated side. Once the table is made it would be a good idea to put some poly on all raw edges to seal them.

  6. #6
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    The way you describe it, you can skip the bottom laminate. Attach 1" mdf to frame and then laminate the top. Contact cement and plastic laminate don't present huge problems with a supported top. A free floating panel is a different beast.

    When you build the frame, I'd recommend you crown the top ever so slightly - say 1/32" or so for a table in the 24 inch range. It it very easy to do precision routing with a crowned top, difficult with a flat top and nearly impossible with a bowl top.
    Tim


    on the neverending quest for wood.....

  7. #7
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    Yes, it is always best to laminate both sided when you really want it to remain flat. The rule is to treat both sides the same.
    Howie.........

  8. #8
    I'd avoid using the oak as it moves differently across it's cross-section, introducing seasonal changes to your table insert. Why not build a torsion box entirely out of MDF?

  9. #9
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    As stated, whenever laminating, you should balance design (same veneers top and bottom) to minimize warping. I can't tell you how many products have been sent to our lab for analysis that warped (skateboards, table tops, etc.) because this basic design criteria was ignored.

    Bob Falk
    Research Engineer
    USDA Forest Products Lab
    Madison, WI

  10. #10
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    Bob, let's say that there is a situation where you cannot use the same veneers on both sides (such as when working with a very costly burled veneer or a rare material), what rules should one follow when choosing a veneer for the 'back' side?

    I presume that rule #1 would be to use a veneer with the same thickness as the display side, and rule #2 would be to use a material with a similar specific gravity? Or are there different rules that should be followed?

  11. #11
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    I want to be clear about what I mean to do.

    The bottom blue portion is 1/8" plastic laminate that I will attach to the bottom of the MDF so that the MDF will not warp.

    The dark brown is 1" MDF that is the primary router top.

    The light brown is the oak frame. I intend to install the MDF into the oak frame flush with the top of the oak frame. The oak frame is 2" tall and the MDF is 1" thick (plus 1/8" for the bottom laminate).

    My intention was then to laminate the entire top, which includes the oak frame and the MDF.

    I intend to use pocket holes to attach the MDF into the oak. I have done some tests so that I know a know how much pressure I can use without crushing the MDF.

    I used an oak frame that I will attach to my table saw table top and to my fence rails. I think that I can easily attach the oak frame to the table saw but that it would be difficult for me to attach the MDF to the table saw.

    Note that although they are not shown here, I intend to run a support structure (like a torsion box) under the MDF with support as close as possible to the section where I install the router lift and also where I run a T-Track for accessories.

    I have practiced threading MDF and then strengthening the threads using CA glue. I intend to use this method to secure the top to the supports that I place under the top.

    My concern was that the top of the oak frame would have laminate and the bottom would not. Based on the comments here, I have a few more questions:


    1. It was mentioned that oak is not a good material to use for my frame because it is not dimensionally stable. I cut the frame using straight grained quarter sawn oak. If Oak is a bad choice here, what would be a good choice? Chris, I did not think about using only MDF because I think that it would be difficult to connect to the table saw.
    2. So do I understand correctly that the plastic laminate may come off the 7/8" portion on the top? If so, then I assume that I should ONLY laminate the MDF and NOT laminate the frame.
    3. It sounds like I should apply some sort of sealer (poly) along all portions that are not laminated. I had been wondering about that (thanks Steve).
    4. Based on a comment by Bill, I wonder if I should simply build a bottom support and then attach the entire MDF top to the frame from underneath (rather than sliding the MDF into the frame). This would be pretty easy to do..... Hmmm, no... With the laminate, the top is 1 1/4" thick. The saw top is 1 1/2" thick and the screw holes are centered 3/4" down, so, all support members would then be placed directly into the MDF, which I expect would not hold.
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    Last edited by Andrew Pitonyak; 01-23-2011 at 8:50 PM.

  12. #12
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    Quote Originally Posted by Bill Orbine View Post
    The oak frame..... is it gonna be the 7/8" edge flush with the top?
    Yes, I meant the 7/8" flush with the top of the MDF without laminate and then laminate the entire top.

    Quote Originally Posted by Bill Orbine View Post
    And just what is this laminate? Formica or wood/ something else? If it's formica or something airtight, you might run the risk of the edges of plastic laminate delaminating in the future if you lamininate on the 2" face of the oak. The point of all this is that I'm concern of the movement of the wood in humidity related situations.
    Standard counter-top laminate from Lowes, so, certainly airtight. Did not intend to laminate the 2" face portion, but I had intended to laminate the entire top so that it is uniform. I can certain crown / round the 7/8 top just a wee bit so that the top is flush with the laminated MDF and not use any laminate on the MDF. Based on Steve's recommendations, I will probably apply some poly to the 2" faces (and the 7/8" faces if I do not laminate the entire top and bottom).

    Quote Originally Posted by Bill Orbine View Post
    I'd say you're fine with the 7/8" edge flush with the top even though I would rather rabbet the oak so that the oak edge doesn't appear as wide.
    Hmm, no particular reason I need to embed the top into the frame, I could place the entire MDF top onto the frame...

  13. #13
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    Thanks for that Steve.... I will certainly do this.

  14. #14
    RouterTable.jpgAndrew, pictures are worth thousand words. Maybe this drawing will help you see my thinking. Of the two, the bottom is better the more I think about it! I saw an issue with the top one. You have to also think the there is expansion and shrinkage of the oak along the thickness of the top, too! I see too much of that in the top drawing and I think the lower drawing is a better way to go!

  15. #15
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    I don't think you'd have problems by applying the formica over both mdf and oak frame, assuming the top edge of the oak is nice and flush with the surface of the mdf, but I do think that both sides of the mdf need to be treated the same, oak frame or no oak frame. And that applies to finish, wood veneer, plastic laminate, whatever. I have seen applications with man-made sheet goods plastic laminated on only one face, but I don't think it's a good idea.

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