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Thread: Really struggling, need help with table top glue ups

  1. #1
    Join Date
    Mar 2014
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    Really struggling, need help with table top glue ups

    Not sure what in the world I am doing wrong but in the middle of building a bedroom set and I just can't get the tops to come out flat with my process. Would really appreciate any help you might have.

    My process for the rough cut lumber.........
    Jointing rough cut poplar on one short side and on long side to get flat. Check my work, perfect
    With flat long side down, run through planer to smooth other long side. Check my work, perfect
    Go to table saw with the 3-4 pieces, run through the above process, and put the good short side against the fence and square up the other short side, perfect
    Return to the jointer and smooth the short side just cut on the table saw, perfect

    Time for glue up, my process........
    I use bisquits (I realize there is a debate about strength) and match the boards up for this process, seems perfect
    Glue each side of each board and insert bisquits, seems right .......... see, this is where I am losing confidence (went from perfect, to seems perfect, to seems right)
    Put multiple boards, with bisquits, glued on each mating side, on the verticle clamping station (a clamp every 12 inches or so)
    Leave it set up for approx an hour and remove, not perfect
    I continue to have a gosh darn bow in my table top

    Tonight I made a set of cauls and re-did the tops. It seems to have helped a lot but still not perfect......and I don't mean, off by a 1/32 of an inch.

    I would really appreciate any help you might give to simplify the joining of boards for a table top. I am at a point that if I have to spend money on something I will. I don't remember the name but I believe there is a "wall clamping station" that can be purchased. Please feel free to suggest anything.

    Thanks in advance and sorry for the long thread.....frustrated.

  2. #2
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    Is it cupping? You must alternate grain patterns of each board for the glue-up.
    Is it warping? Allow lumber to acclimate. If warping still occurs, glue up alternating warps and use cauls to straighten (although this may leave some twist/warp). If possible, don't take down to final thickness - leave as thick as possible. This way you can flattern, or hand-plane out the twist on one side, then send it through the planer for the other side taking it to final thickness.
    Last edited by Bob Carreiro; 05-26-2015 at 11:58 PM.

  3. #3
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    I assume you mean tops for the night stands, they should be fairly small so not to difficult to pull flat when you do the assembly. To prevent cupping you could mill the lumber in stages over a period of a week or two after it had time to acclimatize in your shop for a few weeks (depending on your location and moisture content of the lumber). You could also alternate the clamps (one from the bottom one from the top and so on), cauls will definitely help. Gluing up narrower boards can sometimes make a difference too and try not to clamp the ... out of it. If you're still having issues, dowels instead of biscuits can sometimes make a difference.
    Just my 2 cts.

  4. #4
    Join Date
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    Hi Scott,My guess is your vertical clamping stations is flat along its length or width.
    I clamp table tops up on a flat surface, that I check for twist before I mill my parts square.
    I also have a good square that I am sure is accurate and set the fence on the jointer.Never needed bisket or cauls,i do use spring clamps on the ends were the joint is.Dont give up you'll figure it out.

  5. #5
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    Biscuits are not needed for strength, they are an alignment tool. I never found them particularly useful for keeping the boards lined up so I went back to dowels to keep the boards lined up. For me dowels work much better. If you can keep the boards lined up without the use of biscuits or dowels there is really no need to use them. For me dowel holes are quick on my horizontal boring machine and eliminates one more thing I need to worry about when glueing up.

    Are the glued up boards cupping across the grain of the wood or are they bowing with the grain of the wood?

    Clamping too tight often leads to cupping.

    Go to this page: http://www.wwgoa.com/article/master-the-jointer/ and read the section about half way down titled "Compensating for an out-of-square fence." Always use this method to joint the edges of boards and you will never have to worry about whether your jointer fence is perfect or almost perfect. Your jointer fence can be way off from square and this method will compensate for any variations from perpendicular.

    If you are having problems with the glue up bowing along the length of the grain I would suspect your wood is the problem.

    I picked up three of these pipe clamps off of Craigslist for really cheap. They are supposed to help eliminate cupping. I haven't tried them yet.
    125-026.jpg


    I am usually able to get acceptably flat glue ups without any fancy glue up racks or clamps. I do look forwards to giving these double pipe clamps a try though!
    Last edited by Mike Schuch; 05-27-2015 at 12:49 AM.

  6. #6
    Join Date
    Aug 2005
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    Oak View, CA
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    I've had good luck with this system. I cover the wooden cauls with shipping tape so the glue doesn't stick. I also do glue ups on a flat surface (usually my garage floor). By starting with flat cauls and then pulling them against the work my table tops end up nice and flat.

    125392.jpg
    here's a source:

    http://www.woodcraft.com/Product/125392/WoodRiver-Clamping-System.aspx

  7. #7
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    You clamping station ... are you alternating clamps top and bottom? Most clamp arms bow when tensioned, so alternating helps counteract that force. Of course it requires almost twice as many clamps. Using well seasoned and shop acclimated quartersawn wood removes the material as a possible culprit.

  8. #8
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    Your milling method is "perfect". Don't know about the lumber you are using.

    I process lumber just as you do and have not had any issues that could not be corrected when attaching my top to its base.
    No need to alternate faces in my experience. Just match your faces for the best look after processing as you do.
    The biscuits are a perfectly useful tool for alignment - Festool dominos are even better and easier but biscuits are a useful aid.
    DO MAKE CERTAIN that your biscuit slots are perfectly parallel to your top faces. This could be a source of your problem.

    "Clamping too tight often leads to cupping" A good caution from Mike Schuch. Your boards are already straight - light pressure to pull the joint together is all you need. Cauls are a great option too. Those that Don recommends , though they have limitations appear to be excellent. Important in any case - as you do your glue up check your panels for flat - loosen and move clamps accordingly until your straight edge shows the panel to be flat.

    Also - glue up your panel as close to the finish size as possible - maybe within 3" extra on both ends and 1" overall on the width. Sometimes you can't follow this rule but when you can, why glue up more than you need?

    Sounds like you are doing everything right. I'm frustrated for you. Good luck.

    As for the lumber question -
    I suggest that you mill a few extra boards and then wait - at least an overnight - from the flattening/straightening stage to the glue up stage. Should not be needed but this will allow you to check your lumber again and eliminate the worst offenders before the glue up.
    "... for when we become in heart completely poor, we at once are the treasurers & disbursers of enormous riches."
    WQJudge

  9. #9
    Join Date
    Dec 2010
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    Perhaps a verification in terms is appropriate.

    Bow is a defect along the length of a board.
    A board with a bow in it will rock on a flat surface.

    http://www.woodmagazine.com/woodwork...efects/?page=2

    If the boards start out flat (verified with a straightedge as on your table saw or jointer)
    then the distortion is induced - either by mechanical misalignment on a surface that isn't flat
    or because the wood isn't taking up glue evenly.

    I'm suspicious that the biscuits are swelling and forcing the board into an arc.

    FYI - Many of us don't use anything beyond clamps and glue to align boards like these.
    Last edited by Jim Matthews; 05-28-2015 at 6:39 AM.

  10. #10
    Join Date
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    When gluing up a panel I alternate the clamps above and below and check flatness with a straight edge as I tighten them. Also I glue on a flat surface. I've found that pipe clamps are the worst for bowing with bar clamps next. Bessey k bodies stay flat up to about 36" then they also bow some. So for panels less than 36" wide I can use k bodies sitting on my work table without alternating above and below.
    I stopped alternating grain many years ago when it became nearly impossible to find lumber that was clear on both faces. I go for the best look. My panels or table tops are still flat and remain flat.
    Just a note on terminology, boards have faces and edges.
    Steve Jenkins, McKinney, TX. 469 742-9694
    Always use the word "impossible" with extreme caution

  11. #11
    Ditch the biscuits, use cauls to keep the glue-up flat.

    Also, before applying any glue, do a test run with the clamps and cauls to make sure your panel is flat without any gaps between the boards both on the top and bottom surfaces. You said your machining is perfect but you never really know for sure until everything is pulled tight and there aren't any gaps anywhere.

  12. #12
    What kind of clamps are we using for the glue up? Any chance they are pipe clamps? I have found they really deflect in wider glueups, especially if one really cranks them up.. If glueups are a challange, you will always get much better results from parallel clamps like Bessey k body style

    I do do agree that doing a dry run of your glue up before actually putting glue to the wood is always a great idea. Don't really see any issue with using biscuits, or dowels or nothing at all.. Alternating clamps on the top and bottom is always a good idea
    Last edited by Robert LaPlaca; 05-27-2015 at 8:21 AM.

  13. #13
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    Quote Originally Posted by Scott Brandstetter View Post
    Time for glue up, my process........
    I use bisquits (I realize there is a debate about strength) and match the boards up for this process, seems perfect
    Glue each side of each board and insert bisquits, seems right .......... see, this is where I am losing confidence (went from perfect, to seems perfect, to seems right)
    -- Adding biscuit slots to correctly milled edges should not cause any change in the mating surfaces. Are your biscuit slots deep enough?

    Put multiple boards, with bisquits, glued on each mating side, on the verticle clamping station (a clamp every 12 inches or so)
    Leave it set up for approx an hour and remove, not perfect
    I continue to have a gosh darn bow in my table top
    -- I don't worry about alternating grain patterns arch up, arch down, arch up, etc.). I position boards for the best appearance. If the biscuit slots are not preventing the edges from fully seating together, I would look to your clamping station as the culprit. Is this a pro rig that performs a 4-way pressure when clamping or is it just a row of clamps? I learned to clamp alternating under and over. I also clamp on a flat reference surface with clamps that set flat and stable. This means that the bars of the clamps are also flat so I can use them as a reference surface. You don't mention alignment issues so it sounds like the biscuits are taking care of that for you. I think clamps on the alternate side every other clamp position will be your solution.
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  14. #14
    I am sure not any type of expert but this is what I have done for panels.
    I know this is not what is said about making panels but it works for me.
    I have a very small shop so I can not handle really long boards.

    Starting with 4/4 boards.
    A lunch box planer.
    A Freud glue line rip blade.

    Cut the boards to length plus an inch.
    Run them though the planer to get both sides smooth and flat.
    On the table saw rip one edge of a board, taking off maybe 1/8".
    Flip the board and rip the other edge, again about 1/8".
    Now I lay the boards out like I want them for the panel, alternation grain patterns of each board and mark them 1-to what ever.
    I now mark the edge of each board with a U or a D for up and down, each board will have a U and a D on it.
    On the table saw I now rip about 1/8" off the edge with the U side up.
    Now on the table saw I flip the board over and cut all the D sides with the D down.
    (The up and down cutting is so that if my blade is not exactly 90° they will still go together flat.)
    Now on a flat surface I set up my clamps with half the clamps on the bottom and the other half on the top.

    Again this is how I do it and it works great for me.

    Capture.JPG

  15. #15
    If your finished panel is bowed, my instinct is that the edge of your boards are not perfectly jointed. You mentioned they are 'flat', but are they perfectly square to the faces?

    In my limited panel glue up experience, I can say that cauls, biscuits, clamps all play a distant second to two flat,square mating surfaces. Biscuits will help with alignment; cauls along the edges will help with distributing pressure to give a gap-free surface. But if your boards are not jointed perfectly, then the error magnifies over each successive board - even if you use cauls along the tops, once released, the board will bow.

    A trick people use is to joint mating board edges with the opposite faces towards the jointer fence. This will cancel any error in the fence position. It however, relies on each board having perfectly parallel top and bottom faces.

    Another trick people use is to joint boards 'bookmatched'. Line up the boards in order of assembly, then fold up adjacent pairs (face to face on boards 1, 2, then bottom to bottom on boards 2,3, then face-face on 3,4, etc.). Clamp and joint them as a pair. Again, this way any error is cancelled.

    Also, it really helps me to glue one board at a time. It allows you to work cooler, and neater. It's also easier to nudge boards into vertical alignment and to add more clamps to remove any gaps. If you are a hobbyist like I, you may not mind the sacrifice in throughput.
    Last edited by Prashun Patel; 05-27-2015 at 8:45 AM.

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