Best mirror frame corner joint?

[Martin Lutz]

I am building 2 mirror frames for a friend and am curious about suggestions for the corner joints. They want the corners mitered. The frames are walnut, 2' X 3', made from stock 1" X 2.5"w. some profile. so the question is: pocket screws, biscuits, solid loose tenon, through cut solid spline, or other? Probably 1/4" mirror, the weight of the mirror is my main concern. Any suggestions? Thanks in advance for your help.

[Per Swenson]

Hello Martin,
You must of missed this over the weekend.
http://www.sawmillcreek.org/showthread.php?t=22001

[Martin Lutz]

Out of pocket and offline most of the weekend. However, day late and a dollar short, as usual. Thanks for the heads up.

[Mike Cutler]

Martin. You can never be a day late and a dollar short around here. ;)
45 deg.miters are a very visually appealing joint, it's just too bad that they're not a strong joint by itself.
What is the profile that you need to use. this could impact, the joint that you need to use.
A simple an easy way to reinforce a miter is to use an equalateral triangle at each corner in the back. This will need to be mechanically conected to the miter. Finish the entire back as if it were a framed picture and you hide all the reinforcement.
For big pieces of glass, and mirrors, the rails needs to be physically connected to the upright stile pieces, for moving, and hanging. Be sure to leave some room for float in the mirror, use space balls between the frame and mirror. If the frame distorts at all, it will crack it, that's why folks were suggesting a ply backer board.
I've made a few large picture frames and mirrors. They're not too difficult but you do have to plan for the long haul in the construction.
One more thing to remember. Place felt pads at all the back corners to to stop the walls from being marred by the mirror when hanging. Mirrors like you described might weigh ~20lbs.

[Maurice Ungaro]

Sounds like a half-lapped mitre joint would fit the bill.

[Martin Lutz]

Thanks for the help. I like your ideas and plan on using them. I had not thought of a lot of these.