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Thread: Spoil Board

  1. #1
    Join Date
    Aug 2012
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    Davenport Iowa
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    185

    Default Spoil Board

    Has anyone used 1" PVC for a spoil board?
    Just looking for something humidity would have less effect on.
    Or a sealer for MDF that would help?
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  2. #2
    Join Date
    Mar 2013
    Location
    Memphis TN
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    Default

    I can think of several negatives to using PVC as a spoil board. The major one are the chips from PVC getting tossed around on every job. I take special precautions when cutting plastics to keep that stuff contained and out of my dust collector. Another negative, probably not a concern for you, is that a PVC board doesn't breathe so it won't be usable with a vacuum hold down. Another issue would be cost. It's hundreds of dollars for a decent piece of PVC and almost nothing for a piece of light weight MDF.

    I certainly understand what you're after. The table can change a lot due to temperature and humidity. I suggest looking at using something like PVC as the table base instead of a spoil board.
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  3. #3
    Join Date
    Sep 2006
    Location
    Garland Tx
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    Ken…

    I don’t recommend PVC for a spoilboard unless you have other support under it. PVC, even 1”, will slowly sag between supports. Many years ago, I used to use MDO as a base support and ¼” sintra sheets as the spoilboard. That solved the swelling issue but attaching stuff to the sintra was a problem!

    SG

  4. #4
    Join Date
    Aug 2012
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    Davenport Iowa
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    Default

    Ok Guys a couple of good comments! How about ideas to keep the spoil board stable? Some kind of sealer or just keep grinding it down. Let's bring some life back to what has been a great site!!! Shopbot is a great machine with a lot of smart users. I miss the knowledge from the past!
    Thanks for the few that still contribute!!
    Life is like a project you continue to work on until it's finished.
    Never start a project you don't intend to finish!

  5. #5
    Join Date
    Apr 2013
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    Kennebunkport, Maine
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    4,290

    Default

    Hey Ken,
    Maybe do as TJ is doing in this vid;
    https://www.youtube.com/watch?v=_Nr89_jZacs

    And use Extira as a substrate, and then regular MDF as a raised cutting area?
    You could still use screws or a gun for hold down...still skim it regularly...and use .25, .5, or .75" MDF(your choice) and glue down another layer when it gets thin.
    I just save all my holes and pocket cutting files..and then run it after a new layer is glued down (one my third glue down now).
    Don't know what I'd coat Extira with, but shellac or varnish would probably do the trick on both sides and all edges.

    I've been using a raised cutting area on the Desktop for almost 7 yrs, and love it.
    I use the area outside for fences and clamping, and because Desktop cuts the raised area...You Know the fences butted up against it are good at a glance.
    (going to make my next one with an HDO substrate to get more stable than MDF substrate on this very first one of three I made)
    On the second two I made, I Saturated the MDF substrate with Interlux Teak Oil(it's only naptha/BLO mixed about 50/50) and those two were MUCH more stable!).

    Finally after 6 yrs I took my whole spoilboard off and saturated it with the same finally. Last week was cool and dry...last 2 days 15F warmer and 40% more humidity...
    And today stuck an 1/8" blank rod into spindle, and with feeler gauge checked it..and still registered perfect. Also drove it around at Z-Zero and still flat after last weeks skimming.

    When I make HDO substrate, I'll seal the heck out of all the holes and edges of the HDO!

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  6. #6
    Join Date
    Dec 2011
    Location
    Piedmont, SD
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    700

    Default

    Hey Ken- good to hear from you again.

    I've been using the MDO ply with MDF plenum zoned out for vac, sealed with thinned down yellow glue. Glue down spoil board of 3/4 MDF, seal edges a couple rounds of brushed -on thinned down yellow glue. Grind away as needed. Eight years on the original 2 layers now.

    Recent twist - I received several sheets of 3/8 mystery MDF on a ply shipment. I say mystery, because I didn't order it, driver said it must be dunnage, so it cost nothing . Point being, it was unusually light, so I tried it as a spoilboard with hopes it behaved like the expensive/elusive Trupan ultralight MDF.
    It did.

    However, I did not glue it down- I simply leave it loose on top of the 3/4" glued down layer.
    So - the original spoilboard moves all it wants, I regularly surface the loose top to suit the atmospheric conditions of the day. I read about another guy (DLCW?) who did this with 1/4" MDF. Skinned 2 sides, has a couple on hand and simply keeps them in rotation as the plywood stack is processed.
    You do need to be mindful of debris that could get under the loose one, but overall, I've had no major issues and it vastly extends time period between full replacement of the glued-down spoil board.

    One last interjection - read a comment here years ago about an odd phenomenon with thicker layers of MDF. Logic suggests more air restriction = poor vacuum pull, right?
    However, in practice, it does seem to retain if not slightly increase the pull, as though the thicker layer acts as some sort of vacuum "ballast" or "reservoir" . Seems to me, as my "committed" glued down spoilboard gets thinner, it just doesn't hold as well towards the thinner end of it's life cycle.

    That's just my experience at 3,300 feet above sea level...



    jeff

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