Page 1 of 2 12 LastLast
Results 1 to 10 of 13
  1. #1
    Member
    Join Date
    Aug 2008
    Location
    .
    Posts
    20

    Glue hardwood to plywood

    I have to secure three 6" x 54" pieces of walnut to a plywood buffet top. I have joined and biscuited the three pieces together and I am thinking of gluing the pieces on to the plywood but I am a lttle afraid of expansion and contraction due to humidity. Any thoughts on how to secure the new top. If the boards contract and the glue holds them to the plywood might they split apart lengthwise?
    Thanks
    Siggy

  2. #2
    Member
    Join Date
    Dec 2005
    Location
    Lindale, Texas, USA.
    Posts
    1,449

    RE: Glue hardwood to plywood

    "If the boards contract and the glue holds them to the plywood might they split apart lengthwise?"

    Yes, or they'll warp the whole panel. I'm assuming that since you biscuited them, they're in the neighborhood of 3/4" thick. That's too thick to glue to a piece of plywood. You can glue solid wood to plywood the way you're thinking, but it needs to be thin, like 3/16" or less. If you go thicker than that you're asking for trouble. It needs to be clamped well too, or else it will delaminate. A vacuum bag is ideal, but lots of clamps and cauls will also work.

  3. #3
    Member
    Join Date
    Dec 1969
    Location
    Bradford, Vermont, MerryCanna.
    Posts
    18,751

    RE: Glue hardwood to plywood

    Mmmmmm... what's the orientation of the walnut boards?

    If they're being mounted FLAT against the plywood, yes - wood movement in a glue joint will give ya fits. If they're being mounted with their EDGES against the plywood, there isn't likely to be a problem unless they're ghastly thick (I assume they're 3/4").

    The raw wood will expand & contract far more across the grain than lengthwise, so lengthwise movement can mostly be ignored. A narrow piece will move far less than a wide piece, but you're generally OK up to about 2" of crossgrain width. Anything more than that & it's time for some sort of mechanical fastener... whether screws in slots, "figure 8" connectors, or wooden sliding blocks.

    Can ya show us part of a drawing?

    -- Tim --

    Member of the
    Robert "Limey" Bolton Memorial
    International
    Volunteer Mentorship and Assistance
    Programme

  4. #4
    Member
    Join Date
    Aug 2008
    Location
    .
    Posts
    20

    RE: Glue hardwood to plywood

    The walnut is 3/4" thick. I basically have a panel of walnut 18" x 54" x 3/4 " thick that I am trying to attach to the same size piece of plywood. I was then going to trim everything out around the perimeter with some mitered trim boards of walnut that are 3/4" thick x 1 1/2" wide. Evidently this is not as easy as it looked originally.

  5. #5
    Member
    Join Date
    Dec 1969
    Location
    Bradford, Vermont, MerryCanna.
    Posts
    18,751

    RE: Glue hardwood to plywood

    Ok. So... you're making an "L" shape if ya look at it from one direction? Are the ENDS of the boards in the panel going to meet the plywood, or is the edge of one of the walnut boards going to meet the panel?

    I mean... I assume the panel is 18" wide. that's pretty likely. Does the panel meet the plywood at the 18" end, or at the 54" side?

    If they meet at the 54" side, so the edge of only one of your walnut boards meets the plywood, then you aren't likely to have any trouble with wood movement. If they meet at the 18" end, though, you'll NEED to use some sort of attachment method that allows for movement.

    -- Tim --

    Member of the
    Robert "Limey" Bolton Memorial
    International
    Volunteer Mentorship and Assistance
    Programme

  6. #6
    Member
    Join Date
    Aug 2008
    Location
    .
    Posts
    20

    RE: Glue hardwood to plywood

    No it is like a big sandwich flat on flat. My intent was to hide the dog-eared plywood.

  7. #7
    Member
    Join Date
    Dec 1969
    Location
    Bradford, Vermont, MerryCanna.
    Posts
    18,751

    RE: Glue hardwood to plywood

    Ooo ow. THAT changes the heck out of things. Yeah... you'll have to accomodate movement there - possibly as much as 3/4" of it. Probably less - more probably 1/4" to 3/8" overall - but still it'll move & ya gotta' let it do that.

    Can you get to a blind back side, where you can cut slots & use screws?

    -- Tim --

    Member of the
    Robert "Limey" Bolton Memorial
    International
    Volunteer Mentorship and Assistance
    Programme

  8. #8
    Member
    Join Date
    Dec 1969
    Location
    Rohnert Park, California, USA.
    Posts
    1,874

    RE: Glue hardwood to plywood

    You can't just glue a thin edging to the plywood? For the size, 3/4" is plenty thick for the top. If you want a Walnut top, instead of edged plywood, I would eliminate the plywood and simply go with a solid Walnut top. I can't think of any practical way you could combind the two, without going to more lengths than simply to replace.

  9. #9
    Member
    Join Date
    Dec 2008
    Location
    Houston, TX, USA.
    Posts
    20

    RE: Glue hardwood to plywood

    Sigwood, et al...

    "The raw wood will expand & contract far more across the grain than lengthwise, so lengthwise movement can mostly be ignored. A narrow piece will move far less than a wide piece, but you're generally OK up to about 2" of crossgrain width. Anything more than that & it's time for some sort of mechanical fastener... whether screws in slots, "figure 8" connectors, or wooden sliding blocks." <-- Tim

    If this were my challenge, I would use Tim's suggestion here...First, to cut the plywood undersize in terms of its length and width by about 3/8-inch to that of the solid walnut...This will result in a solid walnut overhang of 3/16 inch around the perimeter of the plywood...That ought to be sufficient for most controlled climate environments such as today's residential or commercial interiors...Then use mechanical means of securing the plywood from its "underside" to the glued-up solid walnut top...This is easily accomplished by using simple pan-head sheetmetal or round head wood screws in a hole of approximately twice the diameter of the screws' shank...The hole is then counterbored approximately 5/16 deep to accept a flat washer whose diameter fits within the counterbore and whose hole closely matches the diameter of the through hole...That is, approximately twice the diameter of the screws' shank but obviously smaller than the diameter of the screws' heads...Install the washers and screws, snugging the screws firmly against the washer but not super-tight...This is a simple, low cost method I have employed for solid wood tops and that has been employed by many, many 20th century manufacturers of solid wood furniture...It seems to work well.

    As for plotting the location of the screws, lengthwise along the plywood spaced every 5 to 6 inches at the centerline of the glued-up walnut and then spaced about every 5 to 6 inches around the perimeter of the plywood.

    Affix the built-up edgework of solid walnut to the solid walnut top...When done your assembly will have a slight gap, as mentioned above, between the edge of the plywood and the solid wood top and interior side of the solid edgework but not visible unless by close inspection from the underside.

    FWIW

    Bruce
    "Keyop"

  10. #10
    Member
    Join Date
    Dec 1969
    Location
    Bradford, Vermont, MerryCanna.
    Posts
    18,751

    RE: RE%3A Glue hardwood to plywood

    For those of us using FireFox (which can't open that bottom picture)...

    Looks good, by the way! :)

    -- Tim --

    Member of the
    Robert "Limey" Bolton Memorial
    International
    Volunteer Mentorship and Assistance
    Programme

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •