Reinforcing Mitered Box Corners

[Andy Compton]

Hi All,

I'm a beginner to woodworking and am making my first box to hold our ever growing Cards Against Humanity set. It's a maple box with a sliding walnut lid and a baltic birch bottom in a dado. In my complete "newb-ness" I decided to miter the corner of the box. Is there an easy way to reinforce the corners? My understanding is that the end-grain to end-grain glue-up likely will not last.

Thanks in advance!

[Pat Barry]

Rubber binders

[Bade Millsap]

I typically use hardwood spline like pictured in this link ...https://picasaweb.google.com/lh/phot...eat=directlink

[Jamie Buxton]

Bade's splines are a good solution. You cut the slot for the spline on a table saw. You make a cradle that stands the box on its corner. It runs along the rip fence.

[Jim Andrew]

I use biscuits. If you have a biscuit joiner, it is easy to put them in miter joints. About the best use of a biscuit joiner.

[Bade Millsap]

I should have been more explicit ... check out this google image link and you'll see lottsa examples https://www.google.com/search?q=mite...sQsAQ#imgdii=_

[Art Mann]

Here is a photo of a keepsake box I built for my daughter-in-law. The sides of the box are 3/8" thick. The keys (also called splines) are the thickness of my table saw blade. I have built several of these and the corners are extremely strong. The box is black walnut and the keys and inlay are soft maple.

Click to zoom

Image00001.jpg

[Jeffrey Martel]

Glued up mitered corners are still stronger than the surrounding wood. Putting splines in helps, but isn't really necessary. It's more for decoration than anything else.

[roger wiegand]

Either biscuits (hidden) or a splined miter (exposed). Have done the keys for decorative purposes as well. The spline running the length of the joint or a biscuit helps keep things from slipping during glue up, though tape on the outside of the miter is also great for that.

[Art Mann]

I don't agree with that assessment. Gluing mitered corners is almost the same as gluing end grain to end grain. You need a lot of surface area to get a strong joint in end grain. You don't get that with 3/8" stock I use. 3/4" material might be more successful. I make my boxes and then cut and install the keys. I have dropped a box on the concrete floor before the keys were installed and it came apart due to glue joint failure. The keys are decorative for sure but they are also structural.

There are other ways to make strong mitered corners. One method I have used is a lock miter bit. With this method, the gluing surface area is greatly increased and you get some long grain to long grain contact. Another way is the old familiar finger joint. Lots of surface area and it is all long grain to long grain. Still a third way is to cut a groove along the length of each beveled face and then install a true spline the length of the joint. Unfortunately, these methods aren't available on the OP's current project.

[Jeffrey Martel]

I don't agree with that assessment. Gluing mitered corners is almost the same as gluing end grain to end grain. You need a lot of surface area to get a strong joint in end grain. You don't get that with 3/8" stock I use. 3/4" material might be more successful. I make my boxes and then cut and install the keys. I have dropped a box on the concrete floor before the keys were installed and it came apart due to glue joint failure. The keys are decorative for sure but they are also structural.

There are other ways to make strong mitered corners. One method I have used is a lock miter bit. With this method, the gluing surface area is greatly increased and you get some long grain to long grain contact. Another way is the old familiar finger joint. Lots of surface area and it is all long grain to long grain. Still a third way is to cut a groove along the length of each beveled face and then install a true spline the length of the joint. Unfortunately, these methods aren't available on the OP's current project.

Try it for yourself and see. In practice, as long as you achieve a glue joint that is stronger than the surrounding wood, that's about as good as you can hope for. There is no real structural benefit to it. Especially in a small box application, there is no need for anything additional. Vertical splines help with alignment, but that's about it.

Cut a 45 deg miter, put glue on, let the end grain soak it up and add more, then clamp it together. After a couple of hours, see if you can break it. If it breaks along the glue line, then you know you will need to add something extra to it. If it breaks out the wood, you are good. So far, when I've tested it, there's been no need for additional splines.

EDIT: Also keep in mind that we're talking about a box to hold cards. Strength isn't needed in this case. If I was doing a box for something that would see hard use, but sure I would do something else or add splines. For this case though, you don't need it. I've built many, some with splines and some without. None have failed yet.

[glenn bradley]

I too use miter keys.

Miter-Key-Jig (9).jpg . Miter-Key-Jig-in-use 006.jpg . Box-swap-2011-waxed-small.jpg

[Jerry Olexa]

splines or biscuits.....

[John Sincerbeaux]

Try it for yourself and see. In practice, as long as you achieve a glue joint that is stronger than the surrounding wood, that's about as good as you can hope for. There is no real structural benefit to it. Especially in a small box application, there is no need for anything additional. Vertical splines help with alignment, but that's about it.

Cut a 45 deg miter, put glue on, let the end grain soak it up and add more, then clamp it together. After a couple of hours, see if you can break it. If it breaks along the glue line, then you know you will need to add something extra to it. If it breaks out the wood, you are good. So far, when I've tested it, there's been no need for additional splines.

EDIT: Also keep in mind that we're talking about a box to hold cards. Strength isn't needed in this case. If I was doing a box for something that would see hard use, but sure I would do something else or add splines. For this case though, you don't need it. I've built many, some with splines and some without. None have failed yet.

Ive been making and selling decorative boxes for a long time. I would not sleep well at night knowing I sold a box that had any joinery that was not "mechanically" joined. Many of my boxes have small trays that also get mechanically joined. I mostly use blind tendons cut with a multi-router.
The OP stated he was new to woodworking. Might as well learn by challenging himself to be a "craftsman". A Craftsman cares that his joinery will last not a few years, but...lifetimes.

Sincerbeaux.com

[Prashun Patel]

I've been experimenting with glue sizing and that really helps to improve the strength of mitered joints. A lot of the glue in a butt or miter joint wicks into the surface of the wood before it can dry. Pre-wetting the joint with thinned glue, waiting an hour, then sanding any nibs and re-gluing seems to result in a stronger joint than just gluing them outright. When I say 'seems', I mean, after a week, it takes a little more force for me to break apart than an unsized miter glue up. That ain't science, so take it FWIW.

I prefer to domino (or biscuit) my miters if for no other reason than it makes clamping a lot easier.

depending on the thickness of your sides, you can also pin them from the outside with 1/4" dowels. There are ways to make those pins decorative with spacing or staggering them between the front and side.

you can also spline the joint by running slots along the length of the miter. I personally find this harder than keys, but keys do require a jig.