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Post Planing cupping

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  • Post Planing cupping

    I ended buying the Ridgid jointer and planer. Over the last 10 days I've put them both together and "played" a bit - checking settings, etc. I found that I had to lower the outfeed table on the jointer a 'smidgeon' as the board I was planing (or jointing) was getting stuck on it. I think I got that worked out. Conversely, I had to raise the outfeed table on the planer about the same amount.

    I planed and jointed one side and edge of a 2.5 ft x 6" piece of maple and went to bed with a grin . A couple days later, after "tweaking" the planer, I planed the other side of the same board to 1/2" thickness, using mostly small cuts of 1/32 - 1/16 (the board started out about 1.25" on one edge and 9/16" on the other edge). I was so happy with the results I brought the piece into the house and placed it on the kitchen table to show the missus in the morning. I went to bed that night with an even bigger grin on my face .

    Then came the problem-the board left in the house on the kitchen table had cupped slightly!! Not alot, but enough to really screw up a project - probably 1/16-3/32". Now my grin turned upside down . The board came from a lot (about 350 bf) of maple I bought at auction and has been stacked in my detached garage/workshop since the end of August.

    Any ideas? I do not have a moisture meter, but would have figured that this board would have been in the right range ( it on the top of the stack too).

    Thanks to all for the input.
    Last edited by Mad Lou; 12-22-2006, 11:03 PM. Reason: clarification

  • #2
    How much heat you got in the kitchen?
    From your workshop to the kitchen is likely a change in humidity, that could cause some cupping.
    Also, if the wood was not dry enough before planing it could cup within an hour after planing depending on the environment.


    • #3
      Your house is likely significantly drier than your garage. Since you placed the board on your table only one side was exposed to the elements and lost moisture from that side causing it to shrink slightly. If you flip the board or sticker it so air can get at both sides it should return to flat. A faster option is to put the shrunk side (concave side) down on your concrete floor, this will quickly add moisture to the shrunk side and return it to flat. You need to monitor it closely as it will not take long (an hour or less) for the board to flatten, leave it too long and it will warp the other way


      • #4
        Did you remove the same amount of material (approximately) from each face when planing? If not this can cause cupping.
        "It's a table saw, do you know where your fingers are?" Bob D. 2006


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