Joining Picture Frame Corners

[bob ware]

Hello everyone. Been a long time lurking member but very few posts.

I could use your thoughts/suggestions about joining/connecting the corners on a fair sized picture frame I'm making for my daughter. The frame is made from 2x2 padauk which I've cut using a combination of router bits and table saw for the design. Size being 24x30. My initial thought was to use pocket screws but wasn't sure this would be the best approach. Plus, drilling the holes would present a challenge since I have one side which is very uneven. Another alternative is the corrugated metal fasteners but wasn't sure these would be strong enough due to the size and weight.

What say the brain trust here on how to approach this? Appreciate your thoughts/suggestions.

Thanks,
Bob

[Jim Matthews]

I suggest splines, cross grain. These can be set in with a handsaw or on the table saw.

Search splined miter joint. If you have a router table, it's fairly simple.

[Stephen Musial]

If the back is flat, rout in a recess for flat L brackets like this (but recessed flat)

281227

[bob ware]

Both good suggestions. I neglected to mention I also have a biscuit tool.

[Darren Almeida]

On bigger frames, I usually biscuit the mitered corners together.

[Jim Matthews]

Both good suggestions. I neglected to mention I also have a biscuit tool.

That should cut a neat slot, when the corners are held together tightly.
Clamp them down to a solid benchtop, and advance the cutter into the corner.

I would test this, first on something that can be discarded.

For strongest bond, the depth needs to be better than 1/2 the diagonal.
Remember to orient the grain of the spline so it crosses both sides
at an angle to their grain pattern.

You're making something like plywood, with the variation in grain direction
providing more strength.


http://www.youtube.com/watch?v=ViPr5xnf1qM

[Prashun Patel]

Glued miters (done right) can be surprisingly strong, as can biscuits.

I read about (and then tried) pre-wetting the mitered ends with glue, and then coming back 30 mins later to reapply glue to the sealed edges before clamping. That and a biscuit should be very strong.

The trick is getting good clamping on the joint. I haven't found anything better for this than a (time consuming) screwed down clamping frame.

[Yonak Hawkins]

I'm a fan of splines on picture frames, as well. I cut the slots all the way across the mitred face on the table saw, outside to inside and, as Jim said, make sure the spline grain direction is oriented 90° to the joint. For frames that will have to support more weight I install two splines per corner. Normally I pin through the splines from the back side with a micro-pinner and often don't even need clamps.

[Andrew Fleck]

You can also inlay some bowties if that goes with whatever look you are going for. I do this often on mitered frames both for strength and looks.

[Jim Tobias]

As others have mentioned, splines may be the simplest way to go. I usually cut them on the table saw and then either use the same wood(if I do not want them to show up much) or use a contrasting wood if I want to highlight the spline.
But, biscuits, dominoes or decorative rods can also add strength to the joint. I have epoxied brass or copper rods through a miter joint to add strength and decorative contrast.
Jim

[Prashun Patel]

Can you advise how you do this?

[Pat Barry]

That should cut a neat slot, when the corners are held together tightly.
Clamp them down to a solid benchtop, and advance the cutter into the corner.

I would test this, first on something that can be discarded.

For strongest bond, the depth needs to be better than 1/2 the diagonal.
Remember to orient the grain of the spline so it crosses both sides
at an angle to their grain pattern.

You're making something like plywood, with the variation in grain direction
providing more strength.


http://www.youtube.com/watch?v=ViPr5xnf1qM
So I know a pint is a pound but whats 5 liters?

[Jim Tobias]

Prashun,
Assuming you were asking me about the epoxied brass or copper rods. I use a lipped brad point bit to bore a precise , clean hole into the miter and then use west system 3 epoxy on a piece of brass or copper. If there is any chip out the epoxy fills it. I usually rough up the surface of the rod before applying the epoxy to hopefully give a better surface on the rod for adhesion. After it dries, I use a pair of Guitar fret snips to cut them as close as possible to the surface. If not it takes forever to grind/sand them flush. DAMHIKT I don't think it makes the joint as strong as splines, but the corner of a shadow box or a picture frame should not be under that much stress the corner on a hard surface. 4th picture is of a finished game box with brass rods(maybe 3/8" rod..I forgot) Last picture is some wenge splines in a wormy chestnut shadow box . Below is a couple of pictures of various corners before and after. Also a picture of regular splines before being trimmed.
281274281276281277281275281273 unless dropped on

Jim

[bob ware]

Ya'll have given me a lot of great suggestions which I really appreciate. Now to decide which one to use. I like the thought of the splines using contrasting wood -- I have some home dried pecan which I think would look great for this. However, with Jim's pictures using the brass rods is also very appealing.
Decisions decisions.........;)

As I've seen so many times in the past folks are great.

edit -- name correction. My apologies to Jim.

[Yonak Hawkins]

Can you advise how you do this?

Sure .. I cut a slot in the mitre faces with the mitred edge flat on the table saw and with either the frame top side or bottom side against the fence making sure to keep the same side against the fence for all ends of all rails. Unless the rails are unwieldy, I do this by hand, not needing a jig. Usually, cutting the slot closer to the back of the frame results in the most hidden spline.

Then I cut the splines slightly undersized in thickness and width so they don't bind when I put the frame together, making sure the grain orientation is across the joint. I rough out the splines such that, when inserted, they are clear of the glass insert area on the back and the outer edges proud of the frame edges.

Then it's a matter of gluing up the slots and the splines and putting it all together. I lay the frame, face down, on a flat surface, tighten up the corners by hand checking for alignment and squareness as I go, and shoot pins through the splines from the back side. The pins should be long enough to go through the splines into the frame on the other side. At this point, unless the frame is especially large, it can be handled enough to wipe off extra glue.

Rarely does the frame not lay flat, but if it does not, I lay a plywood sheet on the back and a weight, if necessary. Then I wheel it into a shop corner and be sure not to disturb it until it's dry. When dry I trim the splines.

[Jim Matthews]

It's important to recognize that the cross section of whatever reinforces a picture frame corner
cannot be so bulky as a dowel or pin without distorting the show face or twisting the frame.

The rear bracket application is simple, but relies on screw fasteners.

The biscuit cutter mentioned by the OP is a simple way to cut slots, but those will have a curved bottom.
If the biscuits that fit have a straight grain pattern, they could be inserted as a spline,
and trimmed flush to the side of the frame.

As mentioned above, "sizing" the endgrain of the miter joint can add appreciable strength.
Glue joints are strongest where long grain fibers meet.

Miter joints are weak as they're mostly endgrain.

http://paul-flores.com/downloads/Joinery_Failure.pdf

[bob ware]

Jim Tobias -- your brass rod suggestion won out. Thank you for posting the pictures as that sold my bride on the idea. I made up a sample this morning using 1/4" and 5/16" rods in a scrap of the padauk and it is a beautiful highlight to the piece.

Thanks again everyone for all your suggestions and insight. You have been very helpful in making this decision. I will post a couple pictures of the finished frame but it will probably be several days before I get it completed.

[Jim Tobias]

Bob,
Glad the bride approved! That is VERY important.
As an added thought, when you are sanding the rods back to flush, if you are using a belt sander or other mechanical sander(which I assume you are), be sure to sand the rods back in short bursts so as to not build up too much heat in the rod. That can cause the epoxy to overheat and release. Again, DAMHIKT
I typically sand the rods flush on a small belt sander with low grit and as soon as they are very near flush, switch over to a random orbital with higher grit.
You can obviously use more than 1 piece of rod in the corners for added strength or decorative purposes especially if the frame material is thicker (or deeper in the case of a shadow box).
Give copper a try also as it looks great with several woods (cherry/walnut/mahogany) and is much easier to sand back.

Jim

[Stan Calow]

For larger, heavy frames I like to use a pinned half-lap joint. Different look, but much stronger joint and avoids the miter gap fussiness.

[bob ware]

Thanks for tips Jim. In the sample I made this morning I used a flat file, but, of course, wood impact was not a factor. I'll most likely use the belt sander method on the real thing.

[Wayne Morley]

So I know a pint is a pound but whats 5 liters?

5 liters of water weighs 5 kg, and at 2.2 lb per kg makes it 11 pounds.

[bob ware]

My apologies for not showing the final results of the completed frame after receiving all the great feedback on my questions. I neglected to take any pictures before my daughter took it so these showing the frame after the print is mounted is all I have at the moment. Hope these show up.

285784285785

[Chris Fournier]

Absolutely none of these suggestions are required for pictures frames. Make sure that the mitres are spot on and then glue them up properly. Done. I have made several dozen picture frames without one spline, screw or complication. 20 plus years later they are all still sound. Keep it simple and keep it real.

[Lee Schierer]

Glued miters (done right) can be surprisingly strong, as can biscuits.

I read about (and then tried) pre-wetting the mitered ends with glue, and then coming back 30 mins later to reapply glue to the sealed edges before clamping. That and a biscuit should be very strong.

The trick is getting good clamping on the joint. I haven't found anything better for this than a (time consuming) screwed down clamping frame.

Since I started doing this, I've yet to have a joint failure. A miter joint is essentially end grain and it sucks up glue, which tends to weaken the joint. By applying a pre-coat of thinned glue then gluing the joints a few minutes later, the joints are not glue starved and are considerably stronger. No need for biscuits or splines in most joints.

[Glenn Lewis]

285932I have 2 approaches to mitered corners, I either avoid them entirely:) or spline them (usually with contrasting wood) Plus it's a nice detail I think...

[Lee Schierer]

If you want really strong mitered looking corners you can always make half lapped miter joints. You get the look of miters and the strength of a half lap.286084