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New at finishing cabinets - need some understanding

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  • #16
    FWIW, I've never had an issue with PVA clue. I've got smaller cabs held together by PVA glue only. Larger ones are glued and screwed.

    I used to use 50/50 PVA/Water as a sealent, but I'm looking for another solution now, as using a water-based sealant like that on MDF could cause as much problems at it solves.

    A sheet of thin ply will hide any butt-joined MDF seams
    Brian Steele
    www.diysubwoofers.org

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    • #17
      I use Titebond for glue, shellac to seal. But that's generally under veneer. And mostly particle board save for my latest Continuum build, which was tape bonded two layer mdf.

      Comment


      • #18
        Originally posted by tvrgeek View Post
        all a miter does is change where the glue line is. No help.
        I don't really agree, you're not only changing where the glue line is with a miter joint... you're eliminating exposed end grain, which is a big issue as far as long-term stability is concerned.

        That whole piece of 3/4" or 1/2" or however thick your MDF or Particle Board or whatever is will expand/contract at a different rate than the face of the panel, and it will likely raise up a bit which causes the 'ghosting' of seams that are so irritating when we build these enclosures then finish them with veneer/poly, or paint etc.

        And using miter joints help with the glue line as well... When the glue line is 1/64th of an inch or likely less, the infinitesimal bit of movement that could possibly occur is basically not enough to cause visible issues. I have made a few mitered cabinets, and they all look as new after several years of existence. Good, tight miter joints are basically like veneer end grain... too thin to be an issue.

        I do agree that a round-over seems to paint/veneer/poly fine. However, there is still the same expansion/movement on the end grain, but since it's curved away from the flat plane of both adjoining surfaces, it's not visible, and therefore not a problem.

        Another issue to consider is the fact that some locales, or home environments have more or less humidity. We live in soupy, southern, NJ, but we run the AC constantly, so it's dry inside, and fairly stable. If we were windows-open people, I bet some of my speakers would look a bit more 'ungood' so to speak.

        Not trying to argue with you brother, just providing a different viewpoint. Talking about this stuff helps us all, especially the new guys.

        TomZ
        *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
        *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

        *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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        • #19
          Personally, I have not experienced ghosting through the PSA veneer I love. All my cabs are buttjointed, exposed endgrain mdf or particle board. The occasional solid wood items are buttjointed, but varnished so the wood seams show anyway. It really helps to have a very square cab.

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          • #20
            The Mariposas and Passive Agressives are solid buttjointed wood. You can feel the seams, but at least to me, look good. The Quarks are PSA maple veneer over 1/2" buttjointed particle board. No ghosting. The green one is an ApexJr buyout quickie plop in the box. Texture paint over 5/8 buttjointed particle board. Slight seams showing where my craftsmanship lagged, but no wholesale seams showing.

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            • #21
              I know we aren't necessarily talking about glue strength but glue shrinkage, as an aside my son and I did a science experiment about 6 months ago (right before Covid shut everything down) to test the relative strength of different wood glues. We did a peel strength test and the results were interesting. If we have a science experiment next year we are going to repeat this but improve our process.



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              I have used PVA glue for years, typically Titebond III, and have never had any issues. After our test I did switch to Gorilla wood glue unless I have gaps to fill, then its PL Premium. If I am gluing other materials, such as plastic to wood, metal to wood, or metal to metal I use 3M Panel Bonding adhesive. It is an epoxy used in automotive repair and, for bonding sheet metal, it is stronger than welding.


              https://www.amazon.com/3M-08115-Pane...dp/B000PEW4MI/

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              • tvrgeek
                tvrgeek commented
                Editing a comment
                PL premium. Great stuff for CARPENTRY. Almost all of your test glues were PVA of one sort or another. I guess just what you could find at the local big box store.
                Panel adhesive has it's uses, but 90% of people use it wrong bonding dissimilar materials and they will fail in time. Classic is bonding fiber glass to metal. Truth, there is NO good way and it will always fail. Can't fight physics.

              • trevordj
                trevordj commented
                Editing a comment
                Ya, we focused on traditional PVA glues and quite a few polyurethane glues (PL Premium, Elmer's Wood glue max, Titebony Polyurethane, Elmer's GlueAll Max, Gorilla Clear, and Elmer's ProBond). With multiple samples tested for each glue brand it was insane! I think we had over 120 joints tested in total. I was surprised the expensive polyurethanes didn't perform as well other than PL premium.

                The one thing I don't like about PL premium is that it doesn't take stain or finish very well. Its excellent for filling gaps and super strong though
                Last edited by trevordj; 08-28-2020, 06:31 PM. Reason: I can't spel very gud.

            • #22
              Originally posted by tomzarbo View Post

              I don't really agree, you're not only changing where the glue line is with a miter joint... you're eliminating exposed end grain, which is a big issue as far as long-term stability is concerned.

              That whole piece of 3/4" or 1/2" or however thick your MDF or Particle Board or whatever is will expand/contract at a different rate than the face of the panel, and it will likely raise up a bit which causes the 'ghosting' of seams that are so irritating when we build these enclosures then finish them with veneer/poly, or paint etc.

              And using miter joints help with the glue line as well... When the glue line is 1/64th of an inch or likely less, the infinitesimal bit of movement that could possibly occur is basically not enough to cause visible issues. I have made a few mitered cabinets, and they all look as new after several years of existence. Good, tight miter joints are basically like veneer end grain... too thin to be an issue.

              I do agree that a round-over seems to paint/veneer/poly fine. However, there is still the same expansion/movement on the end grain, but since it's curved away from the flat plane of both adjoining surfaces, it's not visible, and therefore not a problem.

              Another issue to consider is the fact that some locales, or home environments have more or less humidity. We live in soupy, southern, NJ, but we run the AC constantly, so it's dry inside, and fairly stable. If we were windows-open people, I bet some of my speakers would look a bit more 'ungood' so to speak.

              Not trying to argue with you brother, just providing a different viewpoint. Talking about this stuff helps us all, especially the new guys.

              TomZ
              I round over all the corners. Actually I found all 12 helps smooth the response. I learned not to build boxes with sharp corners 40 years ago so a square mitered corner is irrelevant.

              All this still goes back to the original question which is the seam showing up because of using a glue that sinks in over time, PVA being the poster child. ( PVA is the base for white/yellow, be it Elmers, Titebond, Gorilla or any other water based Polyvinyl Acetate.) This is eliminated by using a rigid non-creeping glue, be powered resin or some epoxies. Hide glue would actually be more than strong enough, but it requires a heated glue pot.

              Any sub-strait under paint needs to be sealed. To do it right, four layers: Sealer, primer, color, clear. Clear is optional, but skip one of the other three, and it will fail. No problem with end grain temperature or humidity.

              A top notch painted finish is not easy or cheap. Solid wood corner boards and veneered ply, even if an exotic, is far easier and cheaper. Spit coat, a few sprayed of poly, cut and buff, you're done. Of course, it you use red oak, you have to fill and seal the grain. It is worth it to buy white oak if that is the grain you want.

              Veneer is a totally different subject that I have limited experience with. Learning slowly. Listening to professional cabinet makers on the woodworking forums.

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              • #23
                I used PL Premium for my three horn subs, because of all the joints that are inaccessible once finished that have to be airtight. PL glops it up real good.

                Best tasting glue

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                • trevordj
                  trevordj commented
                  Editing a comment
                  Hahahahaha! I try not to use the phrase "lol" but I really did almost spit some water across the room.

                • djg
                  djg commented
                  Editing a comment
                  Good, this is supposed to be fun.

              • #24
                Originally posted by trevordj View Post
                I know we aren't necessarily talking about glue strength but glue shrinkage, as an aside my son and I did a science experiment about 6 months ago (right before Covid shut everything down) to test the relative strength of different wood glues. We did a peel strength test and the results were interesting. If we have a science experiment next year we are going to repeat this but improve our process. Click image for larger version

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ID:	1449726 I have used PVA glue for years, typically Titebond III, and have never had any issues. After our test I did switch to Gorilla wood glue unless I have gaps to fill, then its PL Premium. If I am gluing other materials, such as plastic to wood, metal to wood, or metal to metal I use 3M Panel Bonding adhesive. It is an epoxy used in automotive repair and, for bonding sheet metal, it is stronger than welding. https://www.amazon.com/3M-08115-Pane...dp/B000PEW4MI/
                Those results are interesting, thanks for sharing. That must’ve been an expensive experiment😊 As for expansion/contraction of MDF, it’s due to the material wicking moisture to or from the surrounding air. While this happens more on exposed end grain, I believe it happens to some degree with any exposed surfaces. One step often forgotten is sealing the inside. I built & painted a pair of Aviatrx a few years ago and in my haste I apparently forgot this step on one of them. The difference is quite noticable. Sent from my iPhone using Tapatalk

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                • #25
                  Originally posted by jd12 View Post
                  Please share your thoughts on this process and if I am missing anything, or completely wrong about how I am going about this.
                  Here is another suggestion...no matter how many threads you read or YouTube videos you watch you will (almost surely) struggle the first time and learn from your mistakes. So come up with something shaped like a box (maybe a pencil cup, paper weight, etc.) and do a practice build before doing the speakers. I tried piano gloss black and failed and wish I would have just made a bunch of piano gloss blocks of wood (with seams to try to hide) as practice and realized ahead of time all of the little mistakes I was going to make.

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                  • #26
                    Here are glue strength result that are in conflict with those.

                    HowStrongisYourGlue_FWW.sflb.pdf
                    John H

                    Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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                    • #27
                      So, in a word, Titebond.

                      Comment


                      • #28
                        Originally posted by jhollander View Post
                        Here are glue strength result that are in conflict with those.
                        How are they in conflict? We only tested two of the same glues (Titebond III and the polyurethane), and our results for those glues aligned. It looks like they were mostly testing shear strength and I did peel strength. They also looked at joint tightness and wood type.

                        If anything the tests are completely different protocols and still align. They didn’t test gorilla wood glue, pl premium, or super glue all of which were better performers than Titebond III in my test.

                        Another huge difference is I designed my study to specifically look for adhesive or cohesive failure. It was specifically designed to look at the strength of the glue so the overlap of the joints was carefully selected to be sure the wood is not what failed.

                        Almost all glues I tested, and they tested, will be stronger than the wood itself if the wood has sufficient surface area in contact at the joint and the joint isn’t too loose.

                        Comment


                        • #29
                          Heat the cabinets for a couple of days. If you have a trouble light, put a 9W light bulb in it and put it inside the cabinet. Monitor it to make sure it's not getting too hot. Heat will vary with the size of the speaker hole. A few days of heat will stop the glue from shrinking. You can fill from there.

                          Personally, Bondo has ruined more cabinets than it has helped. Bondo cures very hard and it's tough to sand without gouging out the surrounding MDF. If you use Bondo, be very careful to keep your sanding block flat and use a rigid block, like a piece of wood, not a soft block like a sponge.

                          I'd go with something like DryDex. Holy cow, I'm about to take some serious heat for that. Flame on, gentlemen.

                          I'd prime with Zinser 1-2-3 and a 6" roller. I'm serious. Put a couple of coats. Sand to 220.

                          Any rattle can can be good but I've had real good experience with Pep Boys and also with Dupli-Color. With a rattle can, technique is everything. It could turn out complete crap or look like an expensive automotive finish.

                          You want an 8" fan. Practice on a piece of cardboard. Figure out how far back you have to spray to get 8" of coverage.

                          Spray 3 medium coats or 5 light coats. Make sure to spray a little more, after you achieve coverage.

                          Not spraying clear is a mistake. The first time someone sets a mug on the speaker, the finish will be marred.

                          Spray Varathane Diamond clear in the texture you want. It sounds like you want satin. I would think 3 medium coats will be fine. Again, about 8" pattern.

                          If your technique is decent, you can achieve a finish similar to a new car.

                          Attached Files

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                          • djg
                            djg commented
                            Editing a comment
                            Beautiful. I like the Mt. Rushmore camera angle. You might even get me to try it.

                        • #30
                          Does anyone use Formica as a laminate finish for the sides top and bottom of their speaker cabinets?

                          I fail to see where this isn't a good idea that short circuits all the problems related to finishing wood products.

                          I really want to do this but am open to your thoughts.

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                          • djg
                            djg commented
                            Editing a comment
                            I used to use it. A 22 degree laminate trim bit puts a nice edge on it.
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