Scooter67

Plywood Projects and How to join perpendicular pieces

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I am doing a couple of projects using Baltic Birch plywood. I am building a toy organizer, a barn for my daughter's play horses, and a storage cabinet for some tools. I am using rabbit joints on some things and dado cuts on other pieces where the two pieces are not at the edges. I also am thinking about making drawers and using some dovetails. My question is while I am using glue to help join the edges what other things should I be using, nails or screws? Can I use wood screws with pilot holes into the edges of plywood without fear of splitting the wood, the same with screws? The barn will get some punishment from my 7 year old so the sides need to be secured tightly. I am making it out of 1/2" plywood or what Russia has labeled 12mm thick.

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I use a brad nailer when i am building cabinets. this allows the glue to have time to dry which is what is doing most of the work.

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I did some experimenting with 12 mm Baltic Birch a while back, and came to the conclusion that glue is quite good enough. Here a few photos...

post-2037-0-54639400-1320493753_thumb.jp post-2037-0-26250700-1320493871_thumb.jp

post-2037-0-62824200-1320493886_thumb.jp

I didn't use the dowels in the end.

If you do decide to use nails, I have two suggestions. First use Marc's blue tape method to limit the area that you need to apply filler afterwards - put the tape down, hammer in the nail, add filler over the tape, then remove the tape. The second suggestion is to put the nails in at an angle (think dove tails), it might only be psychological, but the mechanical action is greater.

John

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I use a brad nailer when i am building cabinets. this allows the glue to have time to dry which is what is doing most of the work.

I do not have a nailer but I was thinking of nailing that with brads but at a small angle like Toe Nailing. I was also thinking that the edges will be see, that may be I can use small wood screws or even some threaded wood inserts. I know yellow glue like Titebond II is pretty strong but will it hold up to the rough play of an 8 year old. If this barn comes out decent, the plan is to build a doll house.

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I did some experimenting with 12 mm Baltic Birch a while back, and came to the conclusion that glue is quite good enough. Here a few photos...

post-2037-0-54639400-1320493753_thumb.jp post-2037-0-26250700-1320493871_thumb.jp

post-2037-0-62824200-1320493886_thumb.jp

I didn't use the dowels in the end.

If you do decide to use nails, I have two suggestions. First use Marc's blue tape method to limit the area that you need to apply filler afterwards - put the tape down, hammer in the nail, add filler over the tape, then remove the tape. The second suggestion is to put the nails in at an angle (think dove tails), it might only be psychological, but the mechanical action is greater.

John

The glue seems strong but I am not sure how strong and I am afraid to nail on the ends of plywood because it might separate the layers. I was thinking maybe small screws like #2 or #4 size.

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Drill pilot holes for the nails, and use a hammer, not one of those air compressor nailers. Cheaper and faster than screws. Worth a try perhaps.

John

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I've probably built over 100 different cabinets in some form or another. Most of them were constructed using rabbits/dados, glue and a brad nailer. The nails just hold everything in place until the glue dries. Over time, nails and screws come loose from wood movement and use (or abuse). The glue is holding everything together. If you don't mind the look of screws, they'll work to make construction easier. Otherwise, you need a ton of clamps to hold it together until the glue dries. If you're looking for strength in the joint, increasing the gluing surfaces is more important than the type of fastener you use. Use a full dado instead of just a rabbit, or use some type of locking joint.

This might be a time to buy a Kreg jig, I love mine. The screws can be hidden easier and they make construction a breeze.

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I've probably built over 100 different cabinets in some form or another. Most of them were constructed using rabbits/dados, glue and a brad nailer. The nails just hold everything in place until the glue dries. Over time, nails and screws come loose from wood movement and use (or abuse). The glue is holding everything together. If you don't mind the look of screws, they'll work to make construction easier. Otherwise, you need a ton of clamps to hold it together until the glue dries. If you're looking for strength in the joint, increasing the gluing surfaces is more important than the type of fastener you use. Use a full dado instead of just a rabbit, or use some type of locking joint.

This might be a time to buy a Kreg jig, I love mine. The screws can be hidden easier and they make construction a breeze.

I will have to look and see what a Kreg Jig is. I am attaching some pics of a design idea on using dovetails for a shelf type toy organizer. I should have got some pics of what the whole things looks like. I am hoping everyone gets the idea of what I am trying to do. I know I can cut the dovetail groove okay but one the board that will be a support, how would you cut the dovetail so that only half the thickness of a board is cut at a time? I do not have a router table yet.

post-2096-0-29610600-1321743350_thumb.jp

post-2096-0-58923400-1321743363_thumb.jp

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What you are making is called a sliding dovetail. It can be tricky to get them to fit right - they tend to bind when you are sliding them in. A nice heavy mallet may be necessary.

Most people use dados instead of sliding dovetails for these sorts of joints. They seem to be strong enough. Modern glues are very strong, so we don't need as much fancy joinery as we used to. Even with dados, the joints will be strong without any screws or nails.

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I personally wouldn't use a sliding dovetail with plywood. That joint, if not done absolutely perfect will require a lot of force to slide together (or will be too loose). I find sliding cross grain like that on ply is asking for difficulty. As BC has said, I would go with a dado and glue in that situation. If milled correctly, it will be extremely strong.

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I have built dozens of drawers out of 1/2" BB plywood over the years. I join the sides, backs and fronts with dado or rabbet joints and yellow glue (titebond 2). Some of these drawers have been is service for 15 years and I have never had a joint fail. The drawers range in depth from 2" to 10" and include my shop and office furniture, kitchen base cabinet pullouts and the furniture in my wife's sewing room.

Most of the drawers are built by cutting dados into the sides and gluing the fronts and backs into the dados. After the glue is cured, I cut the overhangs in the front off leaving a rabbet and a flush face to mount the decorative front. In some cases I left the overhang in the back if there was depth in the case for it. This makes it a lot easier to assemble the drawers.

An alternate is to cut the dados in the front piece and the back of each side. In this case you can leave the overhang in place to cover the ends of the slide hardware and eliminate the need for a decorative front.

I have never added any nails, glue blocks or other hardware to strengthen the joint.

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Thanks everyone. I think I will use the dadoes and rabbet ends for my organizer. Jack, I have no idea what corner glue blocks are. I think the dovetail would work but I was wondering how to get the dovetail end on the long sliding joint.

If I am using 18mm thickness plywood for the legs and 12mm for the top and middle shelf. How deep should I be making the dado cuts for these? My plans call for a 1/4" deep (6mm) dadoes. Is this to shallow. I have the plywood boards cut to width but no to length yet.

Again, thanks for all you help.

Scott

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Slilding dovetails are really easy to do even in plywood, The trick is to make sure your plywood is dead flat when cutting the joint. Even the slights warp will transfer to the cut and make the joint to tight. Lay the piece on a known flat table. Joint a board long enough to clamp to both sides of the table to be used as a fence. The board will force the plywood flat. cut your dado side first.

The tail side need a similar method. Cut them on a router table standing on end. Clamp a jointed board across the tail board just above the fence to force it flat.

1/4 will be plenty strong but I would not use an exact measurement with plywood. I would measure down the edge to get the depth into a center of one of the plys. If there is a thicker one use that one as your depth.

Don

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Slilding dovetails are really easy to do even in plywood, The trick is to make sure your plywood is dead flat when cutting the joint. Even the slights warp will transfer to the cut and make the joint to tight. Lay the piece on a known flat table. Joint a board long enough to clamp to both sides of the table to be used as a fence. The board will force the plywood flat. cut your dado side first.

The tail side need a similar method. Cut them on a router table standing on end. Clamp a jointed board across the tail board just above the fence to force it flat.

1/4 will be plenty strong but I would not use an exact measurement with plywood. I would measure down the edge to get the depth into a center of one of the plys. If there is a thicker one use that one as your depth.

Don

Thanks Don. I think I understand you correctly. I will let you know how this comes out. It is something I will be working on up til Christmas.

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