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Thread: hardening an MDF torsion box top

  1. #1

    hardening an MDF torsion box top

    I'm going to be building one of these to top a mobile outfeed/assembley/work table. The plan is to use 3/4 MDF and support with a 8"ish grid. It'll be around 3" thick and edged with hardwood.

    Any sage advise from those who've done this before? How has it held up?

    I was also wondering about using a thin expoxy to harden the top some more. Necessary?
    https://two-bit-woodworker.blogspot.com/

  2. #2
    Join Date
    Jul 2007
    Location
    NE OH
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    2,615
    You could consider using MDO plywood instead of MDF. It has phenolic impregnated paper as outside layers and I've found it to be sturdier than MDF, and nearly as flat.

    MDO can be a little hard to find, but Menards carries it and I think most lumberyards can get it. More $$ than MDF, though.

  3. #3
    Join Date
    Mar 2003
    Location
    San Francisco, CA
    Posts
    10,304
    formica...

  4. #4
    MDF will work. You can assemble the whole thing with glue and narrow crown staples. If you use screws, one tip is if screwing within 2" of an edge, put a clamp on prior to drilling and screwing will prevent splitting. If you plan on stapling, keep in mind the distance you need to get your stapler inside the grid.

    I agree with jamie you can't go wrong with laminate. I coated mine with a mixture of urethane and mineral spirits. Have to resand and recoat 3-4X/yr.

    If you're going to drill dog holes or make it an MFT type top, layout the grid first and plan your ribs around that.

    If you're planning to use T Tracks, I would not use MDF because it won't hold the screws. Use ply instead.

  5. #5
    Join Date
    Oct 2008
    Location
    Columbus, OH
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    3,063
    I'm in the camp with others about using something other than MDF. However, to answer your question about "hardening" MDF, I used Arm-R-Seal by General Finishes on some MDF shelves in the base of my miter saw bench to help them hold up against every day abuse. 2 coats as the first soaks right in. Worked pretty well. Also ends up a nice chocolate color.
    Brian

    "Any intelligent fool can make things bigger or more complicated...it takes a touch of genius and a lot of courage to move in the opposite direction." - E.F. Schumacher

  6. #6
    I agree with using formica however MDF is prone to warp if you cover just one side. I would paint or seal the underside with something to keep moisture out of it. MDF tends to get soft from humidity anyway and the paint would help.

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