JosephThomas

Spring Joint

28 posts in this topic

Working on a spring joint for a panel glue-up (it's for the top of a sideboard cabinet).  This is my first time, and I've been tinkering with it, and taking them back to the bench over and over (4 or 5 times now), and I'm not totally sure if I have the right amount of gap or not.  Here's my setup, I took successive passes starting in the middle, lengthening the pass each time...

alueHr9.png

At one point I had messed it up and opened up the sides, so that accounted for a couple of the extra repetitions, but still...I'd like to be done with this before 2018 :)

So now if I leave it un-clamped it looks like this (the boards aren't the exact same length, I just have them rough cut to length, so ignore the shadows on the ends):

0nhuEBs.png

CMGyH3l.png

(and here's the gap in the middle of the board...I have no idea if that is too large or not. These are 6/4 walnut boards, approx 5' in length, one is 8" wide, other is 11" wide):

GwIV1Xd.png

Now if I add "light clamping pressure" this is what I see...I have no idea what light pressure means, so I added a single HF clamps in the middle and only lightly tightened it:

wOnjUSN.png

9afLCcb.png

(however in the very middle the gap is smaller but still visible...again, I have no idea if this is too much gap with light pressure or not):

cNLW9OX.png

Then, if I tighten the clamp a bit more (but still just that one single HF clamp, it closes up nicely..again, no idea how to messure whether this is now "medium" clamping pressure or what):

pTNMLbq.png

For those that have done this before, what do you guys think? Am I done? Do I need to have less gap in the middle before clamping it together? Those are 1/64ths on the ruler, for reference, not sure if that helps.  Thx guys.

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That's a bit more than I am comfortable with. The few springs I have done have only relied on a few thou of hand plane shaving after jointing. With boards stacked next to each other, a single thou pass leaves two thou of relief. 

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I have done a couple before but don't know if there is a rule for gap/length. I have always used my gut. When clamping if it feels like you are clamping more than necessary and it feels like you are stressing the joint cut the gap down. I know Tommy mac did a video on them a while back. Can't remember the episode though.

Don't know if this helps but this is the size of the gap in his demonstration. http://tommymac.us/wp-content/uploads/2010/10/SpringJoint_6.jpg

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That's a bit more than I  bring it open but if that is medium clamping pressure.. be done. 

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6 minutes ago, Brendon_t said:

That's a bit more than I  bring it open but if that is medium clamping pressure.. be done. 

Please define "medium clamping pressure" ...lol. It's a HF clamp and it's not completely tightened...but the bar starts to bend after like a single turn, so I have no idea idea how much pressure it's actually applying. I could go back and try to lessen the gap..I'm just worried I will go too far and open up one of the ends, which means more and more time to fix.

23 minutes ago, bradpotts said:

I have done a couple before but don't know if there is a rule for gap/length. I have always used my gut. When clamping if it feels like you are clamping more than necessary and it feels like you are stressing the joint cut the gap down. I know Tommy mac did a video on them a while back. Can't remember the episode though.

Don't know if this helps but this is the size of the gap in his demonstration. http://tommymac.us/wp-content/uploads/2010/10/SpringJoint_6.jpg

Appears similar to my gap, but it's hard to tell for sure...my boards are also 5' long and it's a nice taper toward the widest gap in the middle.

Thx for the responses, guys.

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If you can do that with one of those aluminum hf clamps, that's still medium to me.  

A single  very light pass on each end of one side will lessen the gap if you choose. 

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That looks like a 24" clamp? At that length, those HF clamps bend with very little force, so you're probably good.

I never understood how a sprung joint is supposedly better than mating flat surfaces. Is it really just better to allow a tiny gap in the middle, rather than risk a gap at the ends?

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That looks like a 24" clamp? At that length, those HF clamps bend with very little force, so you're probably good.

I never understood how a sprung joint is supposedly better than mating flat surfaces. Is it really just better to allow a tiny gap in the middle, rather than risk a gap at the ends?

I always thought that it wasn't better just a way to use only one clamp.

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I think that you are pretty close.  Definitely no wider.  You are going to be asking the glue to do extra work compared to a straight joint so don't take the clamps off too soon.  Give the glue a chance to gain some strength.

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Sorry Jt ! I was in the middle of a heated game of dominion with some friends when you were texting me ! I think you might have a smidge too much gap there. Id it were me, I'd take a few passes with the smoother at either end and glue em up !

Sent from my SM-N910W8 using Tapatalk

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1 hour ago, shaneymack said:

Sorry Jt ! I was in the middle of a heated game of dominion with some friends when you were texting me ! I think you might have a smidge too much gap there. Id it were me, I'd take a few passes with the smoother at either end and glue em up !

Sent from my SM-N910W8 using Tapatalk

Yeah I probably will tomorrow. I just don't have a good feel for how much to remove without a lot of trial and error...the last thing I want is to open up the ends.

Thanks all.

3 hours ago, bradpotts said:

I always thought that it wasn't better just a way to use only one clamp.

Interesting. That makes sense I guess, I could totally clamp it up right now with just one clamp...I always figured it was stronger for some reason, like Tony and others mentioned

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< 1/32" over 5' doesn't seem bad but if a few passes on each end gets it closer that would be better. 

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It's a bit wider gap than I would shoot for, especially with the width of boards you have, but try it out. If it opens or still shows after glueup you can always rip it down the joint and start again. You are only going to lose 1/8" to 3/16 off the width. Remember to bring your shop up to temperature stated in the glue manufacturers instructions especially in the winter.

Lightly clamping means not screwing the heck out of the clamp - firm but not having to use a wrench. Just common sense really.

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Or you can use hid glue - liquid and otherwise- so you can reverse the joint if you aren't happy with it.

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I can't help, but thanks for this thread and the detailed pics. Never tried that joint, I'm learning a lot from the responses.

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I would try David Charlesworth's method of making a stop cut with a longish plane starting and stoping an eighth off each end.  Stop when the planes no longer takes a shaving - this will give you a minute hollow.  Charlesworth usually takes a full shaving or two to get flatter but I'd omit these to get a spring joint. To get the humps down you have now, register at the front of the toe on your plane with the cutter just off the piece and move forward. The process is mirrored at the other end.

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I closed the joint slightly with my smoother, I found it a bit nerve racking to remove too much material so I did this in 2 passes very carefully....1st pic is just zoomed in on the center with no clamps, 2nd pic is with light clamping pressure.  I am tempted to call it...but I'm at least going to move on to the 2nd joint (panel will be composed of 3 boards). 

2siRY94.png

K5hpM50.png

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In the current Popular Woodworking, there's an article by Christopher Schwarz on spring joints.  He talks about how it causes the ends of the joint to be under compression and how that is reported to help with seasonal movement.

Here's the description of the article from their website: http://www.popularwoodworking.com/articleindex/how-why-of-spring-joints

 

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i think you got it Joe, nice work!

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6 minutes ago, sjk said:

In the current Popular Woodworking, there's an article by Christopher Schwarz on spring joints.  He talks about how it causes the ends of the joint to be under compression and how that is reported to help with seasonal movement.

Here's the description of the article from their website: http://www.popularwoodworking.com/articleindex/how-why-of-spring-joints

 

Thanks, I will check that out.

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I think it will be a good joint. 

When the gap is closed and across the width is flat and there's no gap in the joint on the otherside it's gooood.Ive found it takes a lot of clamps to squeeze out the extra glue so don't be shy with your clamps.

Im very picky because I don't like glue lines popping up after the finish.

Yours looks very good to me.

Aj

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Nice job. You did a great job orienting the grain to hide the joint.   I can't even find it in picture#2 and I'm lookng for it. 

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8 hours ago, Brendon_t said:

Nice job. You did a great job orienting the grain to hide the joint.   I can't even find it in picture#2 and I'm lookng for it. 

Thx. It's right on the 6" mark still...it doesn't look that good across the entire 5' of length, but I'm pretty happy with it. the 2nd joint isn't nearly as good, but the 3rd board was all I could get.

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