Who uses a sprung joint and why?

[Rich Engelhardt]

I'd like to know what advantage, there is to using a sprung joint.
Doesn't the force created by the wood try to pull the joint apart?

[John Coloccia]

The idea is to make sure the ends never come apart. Personally, I never use a sprung joint. I just try to get a good fitting joint with no real pressure required. Getting that good fitting joint isn't always easy, though. If you're going to miss one way or the other, you'd rather have a sprung joint than one that flies apart at the ends. You can make a slightly sprung joint work but one that has the ends coming apart will fight you the whole way and likely come apart sometime later.

[Sam Murdoch]

The idea is to make sure the ends never come apart. Personally, I never use a sprung joint. I just try to get a good fitting joint with no real pressure required. Getting that good fitting joint isn't always easy, though. If you're going to miss one way or the other, you'd rather have a sprung joint than one that flies apart at the ends. You can make a slightly sprung joint work but one that has the ends coming apart will fight you the whole way and likely come apart sometime later.

'nuff said! :)

[Jeff Duncan]

It should also be mentioned that a good or...."well sprung" ;) ....joint should be very slight. Your not looking to force the wood to close, as much as use light pressure to close it. Something on the order of maybe 1/32" over 4' for instance. You could easily close it with your hands and light pressure, you don't want to be trying to close a 1/4" gap over 4' as it will be problematic to say the least!

I don't really bother with sprung joints either as it's more time consuming to get them just right....unless you have a pattern makers jointer with that feature that is.

good luck,
JeffD

[David Kumm]

They are finicky with a spring joint mechanism on the jointer too. The old timers could do it just by varying the pressure on the board as it went over the cutterhead so most of the old "patternmakers" jointers had the mechanism knob set and secured. The term Patternmaker jointer was in error for all but the Oliver 12 that adjusted the tables side to side to create draft rather than a spring joint. Dave

[Mel Fulks]

I was taught to make sprung joints years ago, it was the standard practice of my employer.I contuied to use it in subsequent employments but I always had to introduce it and overcome skepticism.I did that promising to pay 20 dollars for each panel that ever opened up on the ends.I have made thousands of interior and exterior panels and never had a claim.Today most of the paint grade jobs would be spect out for mdf....but I didn't write the specs,I did the work.It is still a good idea for top quality WOOD work.The best explanation for its use is found in Charles H.Hayward's book Woodwork Joints.I would be glad to explain technique if anyone with an open mind asks. It is a topic many find irritating.

[Kevin Bourque]

I think that sprung joints were popular in the "good ole days" because wood glue technology wasn't what it is today. For that reason I think they are a waste of time today.

[Van Huskey]

I was taught to use spring joints but at some point I got lazy. Since I have not had any problems since I don't see the need any more but I respect the fact it does have its merits.

[Mel Fulks]

Glue mfg. such as Titebond have phone people who always advise against them,because guys ship them pcs.coming apart that have BIG gaps in the middle .They recommend gluing up boards no wider than 4 inches .That is not an option for fine stain grade panneling .If you can get your client to accept it ,I have no objection. Sometimes the crack is close to the joint rather than right on it.That is all that you can promise based on glue strength.The formerly used technique prevented wood splitting as well as joint failure,except wood splits caused by"compression ring set" type shrinkage,which requires repeatedly getting wet.

[Frank Drew]

Boards lose moisture more readily (more quickly) from their ends than from their middle, causing the ends of the boards to become marginally narrower, at least for a time; from my understanding, this phenomenon is what sprung joints are meant to address, and as such they make sense. I've rarely sprung a glue joint, however, and haven't noticed a problem with my glue joints separating at the ends.

David,

Could you explain "draft" in connection with the Oliver jointer you mention above; I'm not familiar with the term used in that sense.

[joe milana]

Boards lose moisture more readily (more quickly) from their ends than from their middle, causing the ends of the boards to become marginally narrower, at least for a time; from my understanding, this phenomenon is what sprung joints are meant to address, and as such they make sense. I've rarely sprung a glue joint, however, and haven't noticed a problem with my glue joints separating at the ends.

David,

Could you explain "draft" in connection with the Oliver jointer you mention above; I'm not familiar with the term used in that sense.

I'll take a stab at it. In my "drawing", the red rectangle represents the cutterhead & outfeed table of the jointer as viewed by sighting down the infeed table. The black rectangle represents an exaggerated view of the infeed table. By adjusting the infeed table in this manner, the workpiece could be tapered (represented by the brown polygon), giving the piece, or "pattern" the ability to be removed from a mold.
237798

[Julie Moriarty]

According to Tommy Mac:
Use a spring joint when gluing board edges together to allow for the expansion and contraction of wood and to prevent cracking and separating.

Watch him make a spring joint.

http://www.thomasjmacdonald.com/media/video.php?vid=401f67810

I love him! He's great!

[Prashun Patel]

The other nice thing about a sprung joint is that the board acts a little like a cambered caul; you require fewer clamps to get even pressure distribution.

Also, in a multi-panel glue up, it's nice to have all the 'springy' parts lined up. In a world where perfect jointing may have been harder to accomplish by hand, and the springs are not properly lined up, adjacent boards can actually act like buffers preventing the internal springs from closing. When they're all lined up in the center, it's easier to draw the entire joint closed. By aiming for perfectly flat joints, you risk minor unintended springs in some areas. By aiming for a spring, it's easier to achieve a smoother transition. That's not from a book, that's from my own experience. I'm sloppy...

[Van Huskey]

I'll take a stab at it. In my "drawing", the red rectangle represents the cutterhead & outfeed table of the jointer as viewed by sighting down the infeed table. The black rectangle represents an exaggerated view of the infeed table. By adjusting the infeed table in this manner, the workpiece could be tapered (represented by the brown polygon), giving the piece, or "pattern" the ability to be removed from a mold.
237798

Thats an excellent stab, you hit an artery.

[Frank Drew]

Interesting; thanks, Joe.

[Jeff Duncan]

As I mentioned I don't really use them as I find them unnecessary in most situations....however for those who do use them...how would you go about gluing up multiple boards? I'm thinking once you get past say 3 boards, your going to have some issues getting all your joints sprung without creating other problems? I'm thinking about a table top where you may have say 6 or more boards to glue up.....what then:confused:

JeffD

[Mel Fulks]

When material is dry ,warm, and dense....like maple the opening is made very slight. Softer wider boards would have a little more opening.The amount is completely and easily controlled according to judgement On the rare event of something like a five foot wide over mantel panel in a hard wood.I made two panels then jointed a real small opening and glued once more. Like anything else in any trade work you get a little guidance and with use it becomes pretty matter of fact in the doing and yet satisfying.