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According to a test Splines actually make the joint weaker somehow. thoughts?

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Forum topic by Jimothy posted 12-30-2020 11:10 PM 984 views 0 times favorited 9 replies Add to Favorites Watch
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Jimothy

67 posts in 1952 days


12-30-2020 11:10 PM

Okay first of all, this is the video I’m referring to: https://www.youtube.com/watch?v=SfyuCvrdvfU

So I am definitely open to the idea that this test is somehow a dud in some way. Personally I have used splines a handful of times in picture frames, decorative boxes, and essentially wherever there is a miter joint that I felt like strengthening. I understand the concept of the spline is that it creates glue surfaces which are face grain to face grain rather than just end to end in a a basic miter joint. I however have never tested any joints myself, let alone before and after adding a spline like this guy does in the video.

If this video is accurate, I can’t imagine how this is the reality of the spline joint, doesn’t make alot of sense logically. Or at least I just don’t get it. I’ve watched a handful of wood joint testing and up until this video it has all made sense and followed the idea that any time face grain to face grain contact was added when previously the joint would be end to end, it added alot of strength, so I don’t know how this would make sense in the case of a spline joint actually reducing the strength.

Any ideas?


9 replies so far

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Meisterburger

32 posts in 250 days


#1 posted 12-31-2020 01:05 AM

If you remove too much material to insert a spline it would in theory weaken the remaining board. Good woodworking would have you use an appropriate dimensioned spline

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EllenWoodHead

154 posts in 388 days


#2 posted 12-31-2020 01:36 AM

I think the video shows the weakness of miter joints, and that splines are effective reinforcements. In the test with no spline the joint popped completely apart. In the test with the single spline the joint separated until it got to the spline, and then the spline resisted separation. It’s kind of an odd test because the leverage is applied in the weakest direction. I wonder how different the results would be if the pressure were applied from the outside instead of the inside of the frame, then it would test the strongest part first instead of the weakest.

Also, a single miter joint is very weak, and a complete frame is much stronger. If the same test were applied to a complete frame it would have to overcome four joints instead of just one.

-- "wood" and "good" rhyme, but not "food"

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Rich

6544 posts in 1601 days


#3 posted 12-31-2020 04:07 AM


It s kind of an odd test because the leverage is applied in the weakest direction. I wonder how different the results would be if the pressure were applied from the outside instead of the inside of the frame, then it would test the strongest part first instead of the weakest.

Also, a single miter joint is very weak, and a complete frame is much stronger. If the same test were applied to a complete frame it would have to overcome four joints instead of just one.

- EllenWoodHead

I agree completely. It would have been a far better test if the entire frame were tested across the diagonal.

If the orientation of the grain is correct, and the splines don’t remove too much material (like a double spline on a 3/4” thick frame), it’s hard to imagine how the spline wouldn’t strengthen the joint.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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LeeRoyMan

1542 posts in 739 days


#4 posted 12-31-2020 04:44 AM


If the orientation of the grain is correct, and the splines don t remove too much material (like a double spline on a 3/4” thick frame), it s hard to imagine how the spline wouldn t strengthen the joint.

- Rich


Plus… he only put glue on the spline, not inside the cuts. He also didn’t put a clamp on the splines. Would have completely changes the results in my opinion.

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Rich

6544 posts in 1601 days


#5 posted 12-31-2020 05:40 AM


If the orientation of the grain is correct, and the splines don t remove too much material (like a double spline on a 3/4” thick frame), it s hard to imagine how the spline wouldn t strengthen the joint.

- Rich

Plus… he only put glue on the spline, not inside the cuts. He also didn t put a clamp on the splines. Would have completely changes the results in my opinion.

- LeeRoyMan

We’ve nailed him. Thanks to EllenWoodHead. And you, LeeRoy. You always come through in a pinch.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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unclearthur

383 posts in 2799 days


#6 posted 12-31-2020 07:43 AM

When you make joints like this, each one will be a bit different. The pieces of wood aren’t identical. Clamping pressures, amount of glue – it all will vary some for each joint.Small inconsistencies will be there. You can even see sizeable variations in his results between joints of the same type.

So though these tests are interesting, you probably need to test 40 examples of each joint, not 2-4, to average out the inconsistencies and produce real results. And even then you are just analyzing the particular failure mode you are testing.

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EllenWoodHead

154 posts in 388 days


#7 posted 12-31-2020 07:01 PM



So though these tests are interesting, you probably need to test 40 examples of each joint, not 2-4, to average out the inconsistencies and produce real results. And even then you are just analyzing the particular failure mode you are testing.

- unclearthur

Those are good points. I like when people share videos or articles like this, they’re thinking and trying to figure something out. They might not be using the best methods, but they’re trying, which I prefer to people who argue without actually testing anything. (Like the nice people on photography forums who fill up threads arguing about things that are super-simple to test, like “what happens when I put this filter on this lens”)

Maybe when I have some free time I will set up my own simple tests. Testing to destruction is always fun :)

-- "wood" and "good" rhyme, but not "food"

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Rich

6544 posts in 1601 days


#8 posted 12-31-2020 11:36 PM

The person who did the video is a social media woodworker. I’m not saying he doesn’t build some nice things, but it’s nothing that many of us couldn’t do. I see his stuff on Instagram all the time. I’d never watched any of his videos before this one.

It all reminds me of a guy on here a couple of years ago who posted a link to one of his videos. Very ordinary stuff, and one of the things he showed himself doing in the video was dead wrong. I pointed it out and he said Instagrammer somebody or another does it that way and he must know what he’s doing because he has 600,000 followers.

That’s the problem out there. I don’t know how some of these guys build the audience they have, but there’s a general belief among their followers that they are experts and will take what they say without any thoughtful analysis. As this thread shows, once you start to analyze their argument, it doesn’t always stand up.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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LeeRoyMan

1542 posts in 739 days


#9 posted 12-31-2020 11:40 PM

I agree Rich, Now how many people are spreading that information?

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