Mitered Panel Doors

[Bob Carreiro]

Looking to make some flat panel mitered doors for some cabinets, but am wondering how to strengthen the miters.

My kitchen cabinets have mitered flat panel doors. When I look at the inside of them, there appears to be a corrogated(?) fastener driven into each corner (slipped between the panel and the datos outer wall) alongside the panel - not across the miter face as I have used them years ago. What are these? Where do I get them? Is there a special gun/tool that drives them? Are they needed?

It puzzels me... a wider style/rail is one thing, but these will be a standard 2-1/4" wide (doors are about 18" W X 36" H). I know a 2-1/4" wide style/rail will not make a strong enough joint held together by glue only (including the glued (ply) panel acting as reinforcement). And I also know a biscut just registers the two peices for the glue up and offers no structural strength to the joint. So what do I do? Do I have to mill splines in these miters?

thx for helping out,
Bob

 

[ehpoole]

Common ways to reinforce mitered corners:

1) Biscuits
2) Tenons
3) Splines
4) Dowels (if enough width and depth)
5) Half-lapping to miter (the front appears mitered, back appears butted)

I'm sure there are others that don't come to mind right now.

The fasteners you refer to are generally used for light-duty applications, specifically picture framing. They come in two forms, a corrugated zig-zag style and a right-angle corner style. They are generally considered light-duty and should not be the primary means of securing the joint if it will be subject to stress. There are tools for pressing them into the wood (using your weight to drive them). They can also be driven with a small hammer (and pair of needlenose pliers to hold them).

Biscuits, which are a type of floating tenon, DO NOT just register two pieces of wood. Like any other tenon, they provide long-grain glue surfaces ideal for securing two pieces of wood -- especially when used in a joint where only end-grain surfaces would have otherwise been glued. So, biscuits are both an alignment and a structural element, the same as any other tenon. That said, the true strength of any tenon lies in its thickness, width, and the depth it extends into each piece. Properly chosen, biscuits usally do quite well in width, but they have limited depth, so are not as strong as a true tenon of equal width and thickness of greater depth. Biscuits are also thin (5/32"), so in thicker boards (minimum board thickness of 3/4") you may either have doubled biscuits (a biscuit slot two biscuits high) or two seperated biscuits (centered, say, at 1/3 and 2/3 points, thickness-wise) for greater strength.

Biscuits can be a good choice due to their simplicity and the speed with which they can be cut and assembled, provided you are not building an heirloom piece intended to survive through the centuries, and provieded that this is not going to be a heavily abused item. If this will be an heirloom piece, or one which will be heavily abused over time, I would suggest choices 2, 3, and 5 from the above.

Others are likely to have other, possibly better, suggestions.

 

[Bob Carreiro]

Thx Ethan. You put a lot of time and consideration into your reply. I'll probably use biscuts (with your "encouragement").

These doors will be used for a vanity and matching wall cabinets that span just over 5 ft. (no heirloom pc) and made from 3/4" oak for the style/rails & 1/4" oak ply for the panels.

Thank you for your imput.
Bob

 

[Kicbak]

Since you are using a 1/4 ply panel you can glue that in place as well (since it won't move like a solid wood raised panel). I use a rail/stile bit for most of my doors with a 1/4 plywood panel. Biscuit will be good for the miter and it doesn't need to be crazy strong since the plywood panel will also hold everything in place.

 

[westisthebest]

I have used both dowels and biscuits. While you always hear that dowels are stronger, they are, but I realized when building kitchen cabinets you don't need that much strength. Not for the extra time it would take to dowel all compared to using a biscuit jointer. It just cuts so much time off the job. i have dropped a few doors over time and they haven't busted, so they should be strong enough for what you are doing.
Chad

 

[terry1166]

You might take a look at the MCLS website. They have a video demonstration of their mitered door frame router bits. They glue the miters together with a round #11 biscuit that they ship with the router bit kit. They also have a slot cutter in the kit for the biscuit.

Terry

 

[Kicbak]

Another thing you can do, if you are already making a 1/4 groove for the plywood. Take the grove and take is all the way around to the miters as well. You can make splines for the miters. Pretty much making just making a floating tenon.