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Thread: Rough or smooth edges when edge gluing boards?

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  1. #1

    Rough or smooth edges when edge gluing boards?

    Hey guys,

    This seems like a minor detail that I forgot which is best. I'll be jointing the edges of some 5'' wide boards together. One edge will be jointed and the other would be a straight line rip from the tablesaw, it might have some saw marks on it.

    Should I also joint this edge before glue up? Or leave the slightly rough edge so the glue better adheres.

    I'm thinking does leaving a somewhat rough edge help the glue bite into the other board as opposed to a smooth edge?

    Thanks

  2. #2
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    The closer the two surfaces mate, the stronger the joint and the less noticeable the joint line.

    Smoothness is good as is tight clamp pressure.
    Howie.........

  3. #3
    Things like epoxy benefit from having something to get a grip on. I make PVA glue joints fit as well as possible. If your rip cuts leave marks you can see but, can't really feel; that's usually good enough for me. Irregularity of any degree will prevent a tight seam and therefor make them more visible or even have gaps; obviously not desired.
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  4. #4
    I see, I see.

    This all makes more sense. I'll just lightly smooth the table saw rip edge with a sanding block before mating the edges. Thank you both for the input. Love this site.

  5. #5
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    I no longer use the jointer for edge jointing glue-ups. I find that my Freud glue line rip blade leaves a ready for glue-up edge finish.
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  6. #6
    Quote Originally Posted by Bruce Page View Post
    I no longer use the jointer for edge jointing glue-ups. I find that my Freud glue line rip blade leaves a ready for glue-up edge finish.
    Do you mean you just rip each side of the board and it leaves a good finish? That's not a bad idea, espceially for those without a good jointer.

  7. #7
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    Yes. As long as the boards are flat and true, and I do not have to deal with any bow, I rip & glue. I get a very nice finish using my Unisaw and the Freud glue-line rip blade.
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  8. #8
    If you lay your boards out, match up your grain and such, then fold the two boards back together, just like you're closing a book, and run both through the jointer together at the same time, you should have a perfectly matched glueing surfaces. The surface does not need to necessarily be rough, perfectly matched surfaces would do you better.

    With a panel made up of multiples of more than two boards, just keep doing it to each adjoining pair.
    Sierra Madre Sawing and Milling
    Sierra Madre, California

  9. #9
    Quote Originally Posted by Damon Stathatos View Post
    If you lay your boards out, match up your grain and such, then fold the two boards back together, just like you're closing a book, and run both through the jointer together at the same time, you should have a perfectly matched glueing surfaces. The surface does not need to necessarily be rough, perfectly matched surfaces would do you better.

    With a panel made up of multiples of more than two boards, just keep doing it to each adjoining pair.
    That's a great idea. Thank you.




    And I'm probably going to get that glue line rip blade by Freud as well. I wonder if they make them for circular saws too?

  10. #10
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    Quote Originally Posted by Damon Stathatos View Post
    If you lay your boards out, match up your grain and such, then fold the two boards back together, just like you're closing a book, and run both through the jointer together at the same time, you should have a perfectly matched glueing surfaces. The surface does not need to necessarily be rough, perfectly matched surfaces would do you better.

    With a panel made up of multiples of more than two boards, just keep doing it to each adjoining pair.
    Yep.. However, I no longer try to run them in pairs. I run them individually in the same "book page" orientation that Damon explained. The reason I changed is that I had a couple foot-faults keeping two boards together, and found it easier to do one at a time. Same principle, though - even if the jointer fence is one-half of one degree off dead-nuts perpendicular, you still get mating edges that leave the surfaces flat. White chalk triangle to orient everything, then run them through the jointer.
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  11. #11
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    I'm with Brian on the Freud rip blade. It's one of the best tool investments I have ever made.

  12. #12
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    Also, clamp pressure is necessary of course, but you do not want to clamp the joint too tightly and squeeze out all of the glue. I firmly snug the clamps and leave it to dry.
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  13. #13
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    >>>> you do not want to clamp the joint too tightly and squeeze out all of the glue

    Actually, PVA adhesive needs to be tightly clamped to develop maximum strength. For example, Titebond recommends

    For softwoods (pine, poplar): 100-150 psi
    For medium density woods (cherry, soft maple): 150-200 psi
    For hardwoods (oak, birch): 200-300 psi

    To achieve these pressures, you need to fully tighten a 3/4" pipe clamp.

    The bottom line is that it is almost impossible to over-clamp a joint.
    Howie.........

  14. #14
    Quote Originally Posted by Bruce Page View Post
    Also, clamp pressure is necessary of course, but you do not want to clamp the joint too tightly and squeeze out all of the glue. I firmly snug the clamps and leave it to dry.
    I think this was covered a while back in a woodworking technical article. Conclusion was that there is no such thing as over clamping ( and the more tightly clamped joints were stronger even ).

    This is what I have stuck in my brain at least. Maybe Im not remembering right so someone correct me on this

  15. #15
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    I think this fits in with this thread re edge preparation and clamping pressure so here goes-

    What are peoples thoughts on allowing the glue to 'soak in' before clamping?

    It has always seemed to be beneficial to me, especially with porous woods and of course plywood where half the surface is end grain. By the time you get all surfaces coated, the first ones sometimes have soaked up the glue and a second coat is required.

    But if you were doing just 2 short board edges, will the bond benefit from applying the glue and then letting them sit for 3-4 minutes before clamping? It seems to me it would, especially with heavy clamping pressure that could 'squeeze out all the glue'?

    Wouldn't it be possible to apply glue and instantly put it under 150 lbs of pressure and squeeze it all out?

    Me, I've always let it 'soak in' first. Folly?

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