Joining A Mitered Corner

[DieselDennis]

I'm making a simple picture frame out of 1 x 3 lumber.  It's kind of big at 36" x 48".  

My plan is a simple 45 degree miter on the corners.  I'm going to put a rabbet on the inside back corner in order to have a place to put the picture board so the whole thing will fit flush against the wall.  

My question is, what's the best way to join the mitered corner?  I don't trust glue alone.   

I've thought about screws from the top & bottom, which will be mostly hidden from normal people.  

I don't have one of those fancy machines that will just mash a clip into the rear of the miter.

I thought about a simple metal angle bracket I can just attach to the rear of the frame.

I thought about doing a half lap miter, but it would be my very first half lap miter, and the length of the boards has me a bit uneasy.  

I've thought about a reinforcing spline, but again, at this size, it would be a hand full.  

What are some other options to join what seems to be a simple miter joint?

[clockman]

dowels if you have a jig. I have seen Scott Phillips use pocket screws.

[Steve N]

First define exactly what you want. There is a flat mitered corner, and a compound mitered corner. I am thinking you mean a flat one, but if you do mean compound that can change your process. 36" x 48" is huge, and will have a lot of opportunity for flex, which will try to open the joint if just glue is used. I would add whichever you can do easily. Dowel, Spline, Biscuit, to the corners to help hold them. I think I would also move from a simple paper backing to using 1/4" ply as a backer to help keep everything rigid, and flat. Nothing throws a frame off more, than unequally cut lengths, so you should use some type of jig, or gauge to make sure your parts are mitered at exact length, and really make sure you are dead on. At the size you are making every little bit will work against you if you are off in length, or the miter isn't 45*. If it is a flat miter you could use metal L's that would screw on to help hold it together, but make sure the corner is clamped tight when putting them on, lest you actually cause the corner to spread.

[MichaelMouse]

Sounds like you might have room for a step rabbet.  One for the backer board, one a bit deeper to insert and glue/screw a plywood gusset.  Been doing for a 36X84 cherry frame for the last 30 years in our community building.  Since 84 is pretty ambitious, it has a crosspiece to control droop in the center.

[fredhargis]

Any chance you would want to skip the miters and just have 1/2 lap joints on the corners? That's an awfully big frame to not have something.

[arthropod98]

i did a frame close to this same size outta red oak a few years ago, and i screwed and plugged for the miters.  it was a pretty dark stain, so the plugs are barely noticeable.  just my 1/2-cent!  

[Bill Wilson]

I second the suggestion of using a plywood backer and fastening it to the back of the frame.  That will really stiffen things up and tie everything together.  Along with that, contrasting splines would be a nice touch, adding some visual interest as well as strengthening the miter.

[Hank Knight]

I agree with the plywood backer suggestion. 1/8" BB ply would be perfect - a lot of rigidity without a lot of weight and it would reinforce your mitered corners.

[jteneyck]

You should build or buy one of my horizontal router tables.  Putting loose tenons in a mitered joint is no more difficult than putting one in pieces meeting at a right angle, or any other angle for that matter. 



As an alternative, biscuits work fine, too, for low stress joints.  I built this frame about 15 years ago to hold a glass panel that weighs at least 15 lbs.



Or glue it up and then cut the outside corner and glue in a spline.  

John

[JGrout]

What are some other options to join what seems to be a simple miter joint?

1x3 frame is big enough to use biscuits  or dowels  or half lap miters or splines or slots and loose tenons 

Pick one they are all over kill past the glue and a few brad pins 

JME.