Splines for strength on a mitred jewelry box. Do I really need 'em?

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Forum topic by Babieca posted 12-04-2014 05:31 PM 3617 views 1 time favorited 22 replies Add to Favorites Watch
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178 posts in 2018 days

12-04-2014 05:31 PM

Topic tags/keywords: joining

I’m making mitered a jewelry box out of 1/2 inch walnut.

I was planning to put maple splines in it (the top and drawer dividers will be curly maple). Now that the box is glued up, I really like the clean look of it without splines.

The end grain miters are getting a little bit of an internal spline from 1/4 inch plywood that is serving as the box bottom/ drawer runner. It is glued into 1/4 deep dadoes at each mitered joint. (After the fact I realized that I should have done stopped dadoes for the drawer runners. Oh well. That’s what learning looks like)

I don’t expect these joints to take a beating. For this kind of application, do I really need the added strength of the splines?

Thanks for your input!

22 replies so far

View jmartel's profile


8572 posts in 2664 days

#1 posted 12-04-2014 05:33 PM

No, you don’t. They do add strength, but a jewelry box is a low stress application. The splines are merely decorative.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View Fred Hargis's profile

Fred Hargis

5760 posts in 3007 days

#2 posted 12-04-2014 05:37 PM

It doesn’t take much to knock apart an unreinforced miter joint,but if you glued those bottoms in, that should be enough.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Andre's profile (online now)


2807 posts in 2320 days

#3 posted 12-04-2014 05:41 PM

I don’t know! fill that box full of GOLD and she may burst! LOL!

-- Lifting one end of the plank.

View jmartel's profile


8572 posts in 2664 days

#4 posted 12-04-2014 05:48 PM

It doesn t take much to knock apart an unreinforced miter joint,but if you glued those bottoms in, that should be enough.

- Fred Hargis

A miter joint is 3x as strong as a butt joint. Check out the FWW test.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View levan's profile


472 posts in 3493 days

#5 posted 12-04-2014 06:03 PM

If you want a clean look but still want to use splines for strength you can hide the spline vertically inside the miter before glue up. I would go ahead and put horizontals in this one for the added strength.
best wishes

-- "If you think you can do a thing or think you can't do a thing, you're right". Henry Ford

View jdh122's profile


1097 posts in 3331 days

#6 posted 12-04-2014 06:05 PM

Take a look at the beautiful boxes made by BritBoxmaker using his ez-miter technique. un-reinforced miters, and as far as I know they don’t fail. I think it should be fine.

-- Jeremy, in the Acadian forests

View a1Jim's profile


117722 posts in 4091 days

#7 posted 12-04-2014 06:16 PM

Miters basically are butt joints which are not as strong as other joints the link above points out that it in the test on was surprisingly strong. I don’t think that is the norm.Butt joints with all end grain just don’t have the strength that other joints have. Do you have to spline a miter in a small box ? No but in my thought it’s a good idea .

Here’s a quote from the above link.

” Though the miter was surprisingly strong, structural limitations
make it hard to recommend the unreinforced miter for furniture making
tasks. When assembled, the joint is angled at the typical
45°. However, as wood expands and contracts over time, the 45°
geometry will change (see drawing, below), causing joint failure “

View CharlieM1958's profile


16284 posts in 4732 days

#8 posted 12-04-2014 06:19 PM

I only use splines when I want them for appearances. I don’t think they are necessary at all for decorative boxes.

-- Charlie M. "Woodworking - patience = firewood"

View shipwright's profile


8381 posts in 3312 days

#9 posted 12-04-2014 07:46 PM

Not necessary. I’ve done some destructive testing myself using hot hide glue on good fitting miter joints and if anyone puts as much force as it took to break them on a jewellery box they shouldn’t own nice things. That said if you want, for your own peace of mind, to reinforce them… vertical splines as mentioned above will get the job (over)done for you.
Just my opinion of course. :-)

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese!

View Neptuno's profile


32 posts in 1832 days

#10 posted 12-04-2014 07:58 PM

I don’t think you need anything, if the joint is neat and tight. Mitered joints like that do not really classify as endgrain joints, as the 45º angle makes for a, lets say, half endgrain only. Be sure to size the 45º miters with diluted glue before the final glue-up, for much added strength, thus guaranteeing that the joint will not starve.

Adding vertical splines, or biscuits of that matter, would facilitate aligning the glue-up, specially if you are doing many boxes.


-- We must all cross the line.

View timbertailor's profile


1594 posts in 1938 days

#11 posted 12-04-2014 08:14 PM

No. With today’s glues, the wood will split before the joint gives way.

Just consider them decoration.

P.S. Very diplomatically said, Paul.

-- Brad, Texas,

View a1Jim's profile


117722 posts in 4091 days

#12 posted 12-04-2014 08:43 PM

Obviously many folks commenting here make more boxes than I do and much more involved boxes too.. I’m a person who over kills most of my construction so it may not be necessary for you to do the same as I do.
End grain is end grain no matter what angle it is cut at. I do agree with that sizing of the end grain will add to is strength .I think the best way for you to resolve this for yourself is by gluing up a test miter for yourself and do your own strength test,to see what you think.

View Babieca's profile


178 posts in 2018 days

#13 posted 12-04-2014 09:04 PM

Thanks for all your thoughts.

I’m going to leave them out. If this leads to catastrophic (or even minor) failure, I’ll update. For future boxes I may go the vertical spline route.

View OldEd's profile


39 posts in 2126 days

#14 posted 12-05-2014 05:08 AM

I do believe that the strength, or lack of same, depends on the wood. As was pointed out above, modern glues are very strong. “Properly glued” joints are strong – I’ve made end-to-end joints which have held up for the past ten years. HOWEVER – I was using a very dense wood: don’t know what it was, I got it as a gift from a friend of a friend, who brought back a few bf from somewhere in S. America.

I’ve also done it with pine – you have to prepare the material by soaking the end grain of both pieces in thinned glue so that it soaks it up and thus you don’t get a glue-starved joint, as was also pointed out above.

True, splines will add strength, but in small things, such as jewelry boxes, they can be a real pain to put in. And a correctly glued joint should withstand most normal stresses.

So go with it…

-- OldEd

View bannerpond1's profile


397 posts in 2412 days

#15 posted 12-05-2014 05:16 AM

Splines are one more step in the process, but I have decided they’re worth it in ease of glue-up in making the miters fit perfectly with less clamping. The peace of mind that I’ve strengthened the joint is worth something. Most folks actually like the look of the spline because it shows it’s hand made.

The bigger the box, the more I’d lean toward using the splines.

-- --Dale Page

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