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Hand Planing a Spring Joint

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Forum topic by Kaleb the Swede posted 09-06-2015 03:30 AM 954 views 0 times favorited 12 replies Add to Favorites Watch
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Kaleb the Swede

1727 posts in 1432 days


09-06-2015 03:30 AM

Topic tags/keywords: question

I have been thinking about this technique for a bit. Haven’t tried it yet.

Question 1
I know that the opening in the middle is only a few thousandths of an inch, will that open over time?

Question 2
Does it matter the plane used (no 4 to no 7)? I.E. better to put more pressure on said plane. Let’s say the length of boards is 2 to 4 feet.

Question 3
How is this better than planing them even (which would offer more glue surface), aside from using less clamps?

I hope this makes sense, thanks in advance.

The Swede

-- Just trying to build something beautiful


12 replies so far

View jmartel's profile

jmartel

6568 posts in 1613 days


#1 posted 09-06-2015 03:53 AM



Question 3
How is this better than planing them even (which would offer more glue surface), aside from using less clamps?

I hope this makes sense, thanks in advance.

The Swede

- Kaleb the Swede

The idea is that it keeps the ends from opening up. If you keep them even or if they are convex instead of concave then there’s a greater tendency for the ends to split on the glue line. By having the gap in the middle, when you clamp them up there is constant pressure on the ends to keep them together. And there’s sufficient glue surface in the middle to keep that from opening up as well.

I think the plane used would be whatever plane you were going to use for planing the edges anyway. Just take a short stroke or two in the center, then another starting and ending closer to the edges, and then a full length pass.

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

View bondogaposis's profile

bondogaposis

4027 posts in 1814 days


#2 posted 09-06-2015 03:57 AM

There is the same amount of glue surface because in order to work you have to close the gap for full contact.

-- Bondo Gaposis

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pintodeluxe

4854 posts in 2276 days


#3 posted 09-06-2015 04:00 AM

I have come to the conclusion that spring joints are useful for breadboard ends. This is true because you only glue the center tenon, and gapping at the ends can be a problem. Cutting a slight spring joint for a breadboard
end helps to keep the ends nice and tight over the long haul.

As far as spring joints for panels and tabletop glueups… I don’t bother. It was a valid technique for shops with too few clamps, because you could close a joint with one or two clamps. If you have an adequate number of clamps available, there is no need to use a spring joint with most applications.

Most any short plane will work. I wouldn’t use a jointing plane, but even a little block plane will work.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Texcaster's profile

Texcaster

1138 posts in 1137 days


#4 posted 09-06-2015 04:08 AM

A well made sprung joint, under normal conditions, won’t open. My shooting board produces a sprung joint I can close by hand.

This is my low humidity time of year, I just braced three guitars. These should keep me going for three months.

In higher humidity I’ll make archtops, a much more forgiving design. A flat top is braced across the grain, the archtops I make have only two tone bars going with the grain.

one clamp and a weight

re pintodelux and breadboard ends. That is how I make workbench ends, only one bolt needed, but a bigger gap than normal.

http://lumberjocks.com/projects/92062

-- Mama calls me Texcaster but my real name is Mr. Earl.

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Kaleb the Swede

1727 posts in 1432 days


#5 posted 09-06-2015 10:34 AM

Thanks a million guys, that makes a lot of sense. I may give this a try on some smaller things, just to get my technique down. Texcaster, that looks like one useful jig.

-- Just trying to build something beautiful

View Texcaster's profile

Texcaster

1138 posts in 1137 days


#6 posted 09-06-2015 10:36 PM

Luthiers, in general, frown on a sprung joint. A perfectly parallel joint is prefered. As you can see from the photo above, sprung, simplifies glue ups. Old habits die hard.

These joints can be held up to the light and closed with minimum hand pressure. A tricky thing to do with two flimsy 4mm plates and a normal sprung joint

One last photo. Redwood, Sitka Spruce and Hoop Pine on the little one, a Kala style bass. A Kala has a 19in scale, this one will be 23in.

Kala demo.

http://www.youtube.com/watch?v=vNPx6RS8PiM

-- Mama calls me Texcaster but my real name is Mr. Earl.

View Logan Windram's profile

Logan Windram

303 posts in 1925 days


#7 posted 09-06-2015 11:07 PM



I have been thinking about this technique for a bit. Haven t tried it yet.

Question 1
I know that the opening in the middle is only a few thousandths of an inch, will that open over time?

Question 2
Does it matter the plane used (no 4 to no 7)? I.E. better to put more pressure on said plane. Let s say the length of boards is 2 to 4 feet.

Question 3
How is this better than planing them even (which would offer more glue surface), aside from using less clamps?

I hope this makes sense, thanks in advance.

The Swede

- Kaleb the Swede

1. No, the glue in that connection will be stronger than fibers in the board, so it will not open up.

2. I think the 5 is perfect for the spring shavings, I’ve never tried longer, I’m sure you can use anything that is controllable

3. Same glue surface either way. I honestly don’t worry to much about spring joints, but I do plane mated surfaces so the don’t slip on each other. Instead, I’m a glue slut and make sure my clamping process is flawless.

View lateralus819's profile

lateralus819

2236 posts in 1352 days


#8 posted 09-07-2015 12:26 AM

First thing I thought of when I heard that ukulele was an ashbory bass. nice work sir.

View jmartel's profile

jmartel

6568 posts in 1613 days


#9 posted 09-07-2015 03:21 AM

Doucette and Wolfe just put out a new video the other day and they show a spring joint right around the 0:55 mark and how they are planing it beforehand. You can see how easily it closes at around 1:10.

https://www.youtube.com/watch?v=ZzXwmqxMbxs

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

View rwe2156's profile

rwe2156

2192 posts in 944 days


#10 posted 09-07-2015 10:44 AM

I don’t have a ton of experience, but I’ve done a few and I think what plane you use depends on how long the joint is.

The biggest problem for me is making sure I don’t plane out of square.

I always thought the reason for this technique is to minimize the number of clamps.
Regardless, I don’t see why its necessary to spend the time doing it if you have the clamps the ends shouldn’t open up if glued properly.

Didn’t they used to do the opposite and use pinch dogs way back when?

-- Everything is a prototype thats why its one of a kind!!

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Kaleb the Swede

1727 posts in 1432 days


#11 posted 09-07-2015 11:08 AM

That is one of the videos I saw Jmartel. It just had me thinking about it

-- Just trying to build something beautiful

View bigblockyeti's profile

bigblockyeti

3668 posts in 1183 days


#12 posted 09-07-2015 01:29 PM

I made a spring joint in the top of a dresser I created in black walnut (~1.1” x 11”) that was about 7’ long. I started with to straight ripped edges and used a #4 smoother set to produce paper thin shavings. I took 4 passes on each of the two edges, first about 18” in the middle of the edge, second about 42” also centered, third about 60” and the final pass the entire length. Cutting both edges this way yielded about 0.015” gap at the middle and while the clamping force required to close the joint to my liking was substantial, it worked great and is still holding well.

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