I have a large number of boxes to assemble, all are full dado construction. Does anyone have a quick way to spread the glue in the dadoes, short of squeezing some in with the glue bottle and then spreading it with a brush? I have a large number of these to do, so every step matters.
From contributor G:
I don't spread glue in the dadoes. I put in the correct amount and it will squeeze itself where it needs to be. The only time I spread glue is on cope and bead doors and edge gluing.
If you are using fasteners (which act as clamps as the glue dries) in conjunction with the dado, even more reason not to worry about it or waste time/material/labor on it brushing it in and cleaning it up after (which means more money in your families pocket).
Do a test piece and you'll see what we mean. If you wiggle it back and forth, the small section of glue on the sides would have to give before the large section of the dado does, right? Unless you are trying to account for an unusual amount of movement/stress on the joint, it really isn't necessary.
Think of it this way - the ply you are using is not glued on the sides, just on the largest surface and there are no fasteners involved and yet it stays together. Not to mention that when your piece is assembled it is also strengthened and held together by it being part of a whole unit. Just curious - what is the nature of the boxes you are making?
Most of our cabinets are tacked together with 18 gauge 1 1/2" staples while the glue dries. As others have noted the edges of the dado are not necessary for strength. If you are really adamant about gluing every surface you simply need to add lots of glue and let it squeeze out, wipe it with a damp cloth.
The larger glue surface is where the end of the panel meets the dado. A proper dado (one that is not loose) already holds the left and right of 3/16"-1/4" sides. If you doubt that the glued sides do not provide that much in the way of strength versus the flat of the dado, try gluing one with just the sides and assemble (using fasteners as the clamps), and one with the flat of the dado. Once dry, remove the fasteners, and try to remove the panel from the dado. One knock with a mallet will unseat the joint with just the sides that are glued. It will take a lot more effort with the one with the flat glued and will most likely not be possible without tear-out. "Mechanical fasteners (screws, staples, KD) provide little strength to a joint. They are just used to hold things in place until the glue sets."
Agreed about setting the glue. However, using dado and rabbet construction, you could easily assemble a cabinet using nothing but screws and have a completely reliable product. Don't forget the totality of the structure. Think of the framing in your house. It has no glue, is made up mostly of butt-joints using nails and yet supplies the strength for all the materials that hang on it including cabinetry. If you doubt that, assemble a face-frame cabinet, and put the frame on the cabinet with pocket-screws only. Then try and get it off. It's not going anywhere. It can't - it's like a clamp wrapped around the cabinet. That said, I still put glue in the dado on the face-frame. Go figure.
Quality construction is never a waste of time. Thinking that adding glue to the sides of a dado, versus glue on the bottom only of the dado somehow makes it more quality construction (especially if the dado is a proper joint and it gets squeezed out anyway on the sides unlike the bottom of the dado) is in my opinion confusing activity with accomplishment and a waste of time, material and effort for very little return.
Joints must first fit properly, not too snug as to squeeze out all the glue and not to loose as to need glue as a filler. Too much glue can make a weaker joint than too little. Glue should be spread evenly to all mating surfaces of the joint and clamped until the glue sets. The greater the glue surface, the stronger the joint. The time it takes to do this properly will not make or break any cabinet shop.
Too many times on these forums, woodworking questions receive business answers. What is good for business usually has nothing to do with good woodworking. Our price driven market today lets us get away with a lot of poor joinery techniques.
"Joints must first fit properly, not too snug as to squeeze out all the glue and not to loose as to need glue as a filler." A snug joint automatically will squeeze out the glue. It has nowhere else to go. The glue follows the path of least resistance, which is ultimately out to the sides of the dado, the smallest glue surface and where it escapes necessitating a wipe-down.
"The time it takes to do this properly will not make or break any cabinet shop." I disagree. You have to apply extra material, take time to brush it into the sides, then clean-up the squeeze-out afterwards, and that's on every joint on every cabinet. Your other option is to simply squeeze the glue on the largest glue surface, and upon clamping (whether through screws or actual clamps), the glue will make it to the sides, but more importantly across the dado bottom where the real strength is.
"Too many times on these forums, woodworking questions receive business answers. What is good for business usually has nothing to do with good woodworking." Unless woodworking is your hobby, I don't see how you can separate the two in the business of woodworking. That said, I'm totally ok if you want to give more of your money to your clients with a method that uses more material and takes longer if that makes you feel you are offering some level of quality versus the method above. In my opinion it is still confusing activity with accomplishment as in the end there is no appreciable or demonstrative difference, but you can only see that for yourself by doing it both ways.
"Our price driven market today lets us get away with a lot of poor joinery techniques." That is not the case, as there is a large market for apartment-grade or starter cabinets. You would not even approach the same level of quality for this market. You also can't sell high-quality cabinetry to the starter market. So you use cheaper materials and quicker assembly methods to push them out the door.