Edge Jointing Question - So-called "Spring Joint"

[Dru Dron]

Hi Folks,

Hopefully this is a fairly simple question (despite the length of my post...sorry!).

I'm gluing up several panels for some raised panel doors I'm building and I'm trying to use my jointer to create what I've heard referred to as "spring joints" between the individual boards making up the panel. This "spring joint" as I understand it refers to the edge joints being slightly relieved in the middle (just a hair) so that the ends touch each other first with the tiniest little gap in the centre so that when the joint is clamped together extra pressure is exerted at the ends where the joint is more likely to be weak.

Having said that, my problem is that I'm having a hard time achieving the slightly concave edges on the boards using my jointer. I have a Taunton Press DVD video by Kelly Mehler called "Build a Shaker Table" in which he uses this technique to make the top of the table. He says in the video that to achieve the concave edges the outfeed table of the jointer needs to be just slightly higher than the cutting arc of the jointer blades. I've carefully tried that and all that seemed to accomplish was that I couldn't feed the workpiece from the infeed table to the outfeed table. It catches on the leading edge of the outfeed table. In hindsight this seems to be what one would expect since the outfeed table surface is higher than the maximum depth of cut of the jointer in this configuration.

I can only assume I've misunderstood what Kelly Mehler is saying to do. Do any of you have experience with this technique? Can you help me master this joinery technique? The door panels I'm making are somewhat on the large side (+/- 32" tall) and I want the panel joints to be as strong as possible (they are kitchen pantry doors and may take a fair bit of (unintentional) abuse over time). The technique seems pretty simple but I just can't seem to get my jointer adjusted correctly to get the required concave edges on my boards. My boards tend to have a very tiny (easily less than 1/64" ) gap sat each end (the reverse of what Kelly Mehler recommends) which could easily be squeezed together during the glue-up but based on Kelly Mehler's video this would result in a potentially weak joint at the outer ends of the panel that could fail over time.

Thanks very much for any advice you can offer!

Dru Dron
Guelph, Ontario, Canada

[michael osadchuk]

Dru

Here is another explanation from FineWoodworking in making a spring joint with a power jointer:

http://www.finewoodworking.com/item/26796/spring-joints-an-edge-glue-ups-best-friend/page/2

However, I've always used a handplane to accomplish the same after getting a straight edge on the power jointer.

good luck

michael

[pat warner]

Best joint is one that is new, arrow straight, square, knife cut and without defect, including being sprung.
Don't waste time on this silliness.

[Dru Dron]

Hi Michael,

Thanks for the link. I just read Gary Ragowski's article and will try his method tomorrow. I think in my own way I tried something similar earlier today but probably not quite as systematically as described in the article. I'll have to give it another go following Mr. Ragowski's procedure more closely.

I've prepared the boards for two of my doors now and they will probably end up being fine the way they are. I'm just a little disappointed/frustrated that I'm having trouble mastering what seems like a fairly straightforward technique. I guess I'll just have to keep working at it. But I suppose that's what woodworking's all about (at least when it's a hobby as in my case). Learning new techniques by being patient and persistent!

Thanks for helping. I really appreciate it!

Dru

[Jack Wilson50]

+1 for what Pat wrote

[doug faist]

Dru - on panels where my joint HAS to be absolutely perfect, I always joint first to as near perfect as I can get. This should result in a joint that can easily be put together with only hand pressure and show no gaps. Then, I take a very sharp jointer plane and take about three swipes along the middle 2/3 of the edge, being careful to keep the plane flat on the edge. These shavings shouldn't be more than .001 -.002", less than paper thin.

This will put just slightly more pressure on the ends of the joint and just about guarantee no gaps opening down the road.

Is this procedure necessary? No, probably not, but it's worked for me numerous times in the past and superstition keeps me from changing. ;)

YMMV

Doug

[Eiji Fuller]

I also agree with Pat.

[Dru Dron]

Hello Pat and Jack,

Thank you for your comments, but I'm not sure I understand where you are coming from regarding my question. It would seem you are criticising me for wanting to master what seems to be a relatively simple technique that at least two well known, and I assume respected, professional woodworkers use (i.e. Kelly Mehler and Gary Rogowski). Is that the case, or am I inadvertently misinterpreting the intent of your comments/responses?

My only intent in posting my original question was to try to improve my skills as an amateur, hobbyist woodworker. Yet the tone of your comments makes it seem like I've committed some sort of transgression or offended you in some way. Wanting to learn how to produce a spring joint for edge gluing a panel doesn't seem like "silliness" to me. Why do you feel it necessary to criticize me for wanting to learn how to make this type of joint? If you feel a spring joint isn't necessary, why don't you just tell me that and perhaps explain why? I'm just trying to learn so I can improve my woodworking skills. That's why I joined this forum in the first place!

I only do woodworking for the enjoyment of it and your seemingly critical comments certainly don't do anything to help in that regard. I wonder now whether I should bother posting any further questions to this forum if this is the type of reaction I'm going to get.

My apologies if my reaction is out of line. I'm just surprised by the rather critical tone of these two responses. I thought my original question was quite innocent and benign. It would seem not though (to my complete puzzlement).

Dru Dron
Guelph, Ontario, Canada

[Dru Dron]

Hi Doug,

Thanks for the input. Maybe I need to dust off my jointer plane, sharpen it up and give it a workout. It might prove easier than trying to master the power jointer approach.

I have no real expertise regarding this whole issue and whether sprung joints are even necessary. I still consider myself a relative beginner woodworker. But given that these doors are for a rather importand piece of kitchen cabinetry I'm just trying to produce the best doors I can and use the most appropriate techniques so that they last a very long time. Hence, I thought I'd ask the folks at Sawmill Creek if they have any advice.

I am much obliged for your suggestions!

Best regards,

Dru

Dru Dron
Guelph, Ontario, Canada

[Darius Ferlas]

Funny that.

I didn't know I was using an actual woodworking technique. The thing is after changing my jointer knives, no matter what I do, the edges show what I what turns out to be "spring-joint". I start clamping in the middle and then move towards the ends, where I don't even seem to need any clamps. I still use them though. Works for me.

[Dru Dron]

Hi Darius,

That's interesting. Sounds like you're accidentally producing the result I'm aiming for but can't seem to achieve if my life depended on it. What you describe regarding clamping seems to validate Kelly Mehler's rationale for using this type of joint when edge gluing (i.e. intent is to strenghen the joint at the outer ends by applying more pressure).

By any chance do you know if the maximum cutting depth/height of your newly installed knives is flush with your outfeed table or slightly higher? Kelly Mehler says the outfeed table needs to be ever so slightly higher than the maximum cutting height of the blades/knives to produce this so-called sprung joint. When I tried to set up my outfeed table this way I found that my workpieces would catch on it. Maybe I'm just raising my outfeed table a tiny bit too far.

Anyway, thanks for your comment. Interesting!

Dru

Dru Dron
Guelph, Ontario, Canada

[Tim Lawson]

Hi Dru,
I'd second what Pat says and ask forgiveness for his terseness. I've struggled to create a sprung joint and don't quite understand the benefits.

Two straight matching edges, especially if you plane the board in bookmatched pairs, works well and clamps up well under modest clamping pressure. Plus you not introducing any additional stress in the board - closing up that sprung joint is adding some additional deflection in the boards. With straight unsprung edges you know they'll match and the the glue will squeeze out evenly.

I tried Kelly's springing method on the jointer and was unconvinced. Your jointer has to be very well tuned. You'll get a much better joint using a jointer plane. Practise on some trial boards first.

The other big thing is to get the clamping spacing figured out so that you're getting even pressure along the edges of the board you're jointing. The 90 degrees cones from each clamp face only need overlap by an inch or so. Use cauls to get that coverage rather than more clamps.

Practice will really help 2x6 or 2x8 are relatively cheap.

Tim

[Bill ThompsonNM]

dru, I just read thru these exchanges-- I don't think pat and Jack were being rude-- it seemed obvious to me that despite "famous woodworkers" opinions they thought that the technique isn't worth the effort --
after many years I can assure you that you will find many experts espousing all sorts of "must do" techniques which in reality don't have any common sense or real purpose behind them. Famous or a tv personality doesn't guarentee best practices by any definition -- sometimes you will just have to find that out for yourself.

[Tim Lawson]

Darius,
Sounds like your jointer knives might be a little high. Check how high they are off the cutterhead. John White's book is a good reference.

Tim

[Dru Dron]

Hi Tim,

Thanks very much for your suggestions.

It's quite possible it is I who should apologize to you and Pat (and everybody else) if my reaction to Pats comment was overly sensitive. It just caught me a little by surprise and seemed unnecessarily critical. In all sincerity I did not mean to offend anyone by my reaction.

That aside, I don't know either whether a sprung joint is really necessary either. It just sounded like a good idea and was trying to achieve it. My jointer isn't the greatest (6" General International) and seems to produce inconsistent results (super straight and flat boards one day, curved and twisted results the next!). The last couple of days, despite my best efforts to fine tune my jointer's alignment, the best I seem to be able to produce is a very slightly convex edge leaving a hairline gap at either outer end of the joint (certainly no more than 1/64" and usually noticeably less than that).

Do you think over time the joint is any more likely to fail because of this small gap at the ends? I'm sure it will be no problem squeezing it together during the glue-up process and with the strength of today's woodworking glues I'm also sure it will hold up in the short term. I'm just curious whether a few years from now there's much chance of these door panels starting to separate as a result of me not being able to achieve a super tight joint prior to assembly.

Any further thoughts?

Thanks again for your insights. I greatly appreciate you taking the time to post a response.

Best regards,

Dru

Dru Dron
Guelph, Ontario, Canada

[Darius Ferlas]

By any chance do you know if the maximum cutting depth/height of your newly installed knives is flush with your outfeed table or slightly higher?


Darius,
Sounds like your jointer knives might be a little high. Check how high they are off the cutterhead. John White's book is a good reference.

Gentlemen, as I said the results I get are purely accidental. I wish I could say I whip them spring joints with ease, but it's just a side effect of, apparently, faults in my jointer set up.

To my knowledge the knives are flush with the out feed table. I use one of those "glass plate plus magnets" jigs. I am pretty sure the reason for my "spring joints" is that the tables are not perfectly coplanar. I have a parallelogram jointer, but I find it extremely difficult to benefit from its alleged superiority. The the little bolts (no idea what they are called) used to regulate the height of the tables keep on slipping on me, so what I have now is about the best I can get. Unless I get real straight edge and try again.

[Dru Dron]

Hi Bill,

I appreciate your insights. I didn't mean to come across as overly sensitive and apologize to Pat and Jack again if that's the case. I was just surprised that my original question would be referred to as "silliness". I was just hoping to learn a little more about this technique in case it was beneficial to my project. I've always felt asking questions is the best way to learn and I've certainly learned a lot by reading this forum.

I'm getting the impression from some of the responses to my original post that I may not really need to worry about achieving a sprung joint, and if that's the case, so much the better. I'll glue up my panels and move on. If they start cracking a few years from now I'll know that I didn't do a good enough job on the joints and I'll try again if I ever need to replace these doors.

Thanks,

Dru

[John Downey]

If you want to spring the joint, a couple swipes with a hand plane is all that is needed.

The purpose of springing an edge joint is to use the tension in the center to compress the ends a little more. Whether it is necessary or not is, as you see, open to debate. I've seen all of one table top joint fail under normal conditions, ie: not due to water damage during storage, etc.

Springing an edge joint certainly isn't a requirement of good woodworking practice. That said, I often will do it on joints longer than about 3', as it doesn't do any harm either, and its very easy to do if you have a sharp plane handy. I don't recommend fooling around with the jointer to do this, but that's just me :D

[Myk Rian]

Drop the outfeed table of the jointer a tad. That will do it.

[glenn bradley]

Gary R is one of my favorite gurus and I'll stop and read or watch pretty much anything he has to say or show but, I don't bother with spring joints at all.

[John Thompson]

I used to years ago but.. find as long as you are getting "butt kiss" joint alignment the entire lengh it is not necessary from my experience with them.

[Frank Drew]

Dru,

I'm with the group that doesn't believe that sprung joints are in any way necessary or superior to ordinary, well-fitted glue joints. In over a quarter century making furniture, I never saw one of my glue joints open up, not at the ends or anywhere else along the glue line (I never got a call-back, at least :D).

However, I believe that some of the older heavy-duty jointers had settings to create sprung joints.

[Chip Lindley]

Dru, the purpose of any "sprung joint" is to insure that the ends of panels do not open up during the glue/clamp process. Unless stock contains excess moisture that will allow it to shrink faster at the ends after the glue-up, there should be no problem with gluing up perfectly straight-edged stock. I have never had a problem with panels which were prepared with stock edge-jointed as perfectly straight as I could possible manage.

A very simple method to spring a joint is accomplished by pressing down harder on the center of the board! An extra smidge can be removed in the middle but not the ends. This too-simple technique requires no misalignment of your jointer whatsoever.

Personally, once I get a jointer set up to cut perfect straight at 90 degrees, I ain't messin' with it!! Not until knife-changing time! Finding the elusive set-up which will allow your jointer to cut straight again, may be more trouble than it is worth, in trying a new technique which may be of small value in the grand scheme of things.

Please do not "read too much" into responses by others, as to what you sense as terseness or rudeness. Folks from different parts of these United States communicate in different ways. "Normal" for a New Jerseyite may offend a mild-mannered Midwesterner. "Everyday" for a Longshoreman may offend a PhD. No doubt, some here are Qwerty-challenged, and elaborate as little as possible. Unless explicatives or epathets or direct attacks are included, take it all with a grain of salt.

[Eiji Fuller]

Say you have a table top you need to glue up with 8 boards if you spring all those joints you will have to delfect the joints on the outside by about a 1/16" or more to get them all to close up. I just dont see the point.

If your jointer leaves a gap between 2 boards than it needs some adjustment. no gap is best. The only joints I have ever had fail are when I used polyurethane glue for some exterior columns. I will never touch the stuff again.

[Howard Klepper]

A jointer doesn't just automatically produce a perfect edge when it's set up well. The stock has to be fed well. Different users will have a different set up, depending on how hard and where and when they press when feeding.

That being said, I agree the best joint is dead straight. If you have to be off, it's better to have the gap in the center, but that's IF.

[John Downey]

Say you have a table top you need to glue up with 8 boards if you spring all those joints you will have to delfect the joints on the outside by about a 1/16" or more to get them all to close up. I just dont see the point.

This assumes the wood is un-compressible, and in that case I would agree. The idea is to put the ends of the boards under a slight cross grain compression because they swell before the middle as they acclimate. I'd bet this is a hold over from the days of hide glue, which I still use. I would also guess your example is over-estimating the amount of spring, but I'll admit to never having measured when I've done it :D

Part of the problem with evaluating the effectiveness is that of the table tops I've seen fail (thought of another, I'm up to two now :D) I have no idea if the joint was a.) sprung, b.) straight, or c.) convex. The other problem is that all our glues have a long enough expected life span that you're unlikely to ever see one of your own joints fail. One of the two tables I've seen fail was 40 years old, high quality factory stuff. The other was less than 10 years old, but was 8/4 mesquite - problem was caused by gnarly grain shearing the joint as it moved. I wouldn't really count on any technique or kind of glue to save that one.

I still chalk it up to personal preference. There's a bit of theory behind it, but I've never known anyone to make a serious study of the question.

Now that I think of it a bit longer, springing must be a more modern practice, as it requires good clamping pressure. Pre-industrial revolution that would have been much harder to achieve, steel clamps being either non-existent or absurdly expensive.

[Mike Wilkins]

I have read about this technique in the past, and thought it was kind of foolish to go through all this trouble to glue up a panel. As long as the edge of each board is straight, and your jointer technique is proper, there should be no need to use a sprung joint. I could see using this method if your lumber is not at a proper moisture level, but you should not be attempting to make panels with wet wood anyway.
Joint straight, glue up your panels, and enjoy the efforts.
Just my nickels' worth.

[John Thompson]

A jointer doesn't just automatically produce a perfect edge when it's set up well. The stock has to be fed well. Different users will have a different set up, depending on how hard and where and when they press when feeding.

That being said, I agree the best joint is dead straight. If you have to be off, it's better to have the gap in the center, but that's IF.

Couldn't agree more... the reason I used to spring joints before I got technique down to an art on the jointer. And you are absolutely correct about gap in the center as opposed to ends. That gap will compress and lock the ends tight but.. gap on ends are very difficult to work with and if you have them you are pretty much dead in the water from the git-go for the most part IMO. haha..

[Michael MacDonald]

A very simple method to spring a joint is accomplished by pressing down harder on the center of the board! An extra smidge can be removed in the middle but not the ends. This too-simple technique requires no misalignment of your jointer whatsoever.


Dru -- +1 for this. I wouldn't think that misaligning the outfeed table is a great idea.... I can't remember where I saw this... but it was probably a video on the intranet.

By the way, when I read Pat's comments on "wasting time on this silliness", I didn't take it as rude... just a clear comment on his opinion for the value of this technique... Since I discovered the technique myself, I have wondered if it was really worthwhile. Pat's point may be right or wrong, but it is a sound idea to evaluate what you are trying to do--is it worthwile, or is it overthinking that which is already good enough. It looks to me like there are mixed thoughts on the creek about that conclusion.

[Cliff Rohrabacher]

Don't waste time on this silliness.

What he said

[Bruce King]

I like to add some biscuits on large glue-ups since they are quick and easy.

[Phillip Ngan]

Dru, I empathize with you as another novice woodworker. I get the feel that most people on this thread don`t use spring joints, so I`ll add a vote for the opposite view. I use spring joints for edge gluing panels because if there is going to be a gap it better not be at the ends of the joint. My intuition (presumption) is that even if the two edges being glued together are perfectly straight initially, the introduction of clamping pressure in the centre will compress the wood in that central region and so cause the outer ends of the panels to splay apart. So my insurance is to use the spring joint. I take a few swipes out of the central region with a hand plane. The first swipe covers 3/4 of the length of the edge, the second covers 1/2 and the third covers central 1/4. I'm guessing that I'm taking 0.001" to 0.002" thick shavings each time. This is really a very shallow spring joint. It literally adds no more than 10 minutes to the project (provided your plane is prepared for taking fine shavings). A pretty small price for insurance against end gaps.

[Rob Woodman]

In an earnest wish to illuminate the 'whether to or not to' debate and not 'add fuel to generate heat' into the topic.

From the book " Modern Practical Joinery" by George Ellis Published in 1902. Reprinted by Stobart Davies ISBN 0 85442 039 8
Re: Jointing of boards- "A long joint should be shot slightly hollow in length to counteract the effect of cramping up, and also to ensure that the ends of the joint are tight up, as these are the most likely points for the air to enter and break the joint."

Ellis then goes on to write about the glue up " proceed to apply the glue ~which should be very hot" and after notes on the consistency, " and standing at one end, with an assistant at the other, grasp the ends of the upper board near the joint (the lower one being in the vice) and rub to and fro steadily, in strokes of about 2ft, until the bulk of the glue is rubbed out, and the joint begins to "drag"."
Ellis then notes about using "cleats and wedges" to cramp up.

Bearing in mind the glue and methods described it would seem that the practice of hollowing a board is one that is not necessary with modern glues and tooling. It is also noted that the practice was carried out on long boards.
If one likes to continue to implement this practice fine, it just seems to be an additional step in the process that adds time to the project.
Regards Rob.

[Michael MacDonald]

From the book " Modern Practical Joinery" by George Ellis Published in 1902....

I bet George Ellis though he was finally settling the argument on this practice once and for all...

I am curious, I saw the argument that clamping pressure in the center of a glue-up would cause the ends to spring apart... how likely is that with clamps at the end as well? and once the clamps are off, I assume the "separating pressure" on the ends goes away?

also curious: does anyone hollow out both boards? or just one side of the joint?

[John Thompson]

"Modern Practical Joinery" published in 1902! haha.. Mr. Ellis was working with Hide glue in those days and 1902 clamping systems. "We've come a long way, baby" as the expression goes with both glue technology and clamping technology. The glue I used when I started in 1972 and the clamps were far from what I have availble in my shop today so I used a spring joint at that time.

As already mentioned I don't after I learned proper set-up and technique on a jointer and working with far superior clamps and glue. I have 14 Jorgy Cabinet-masters setting on a 60" x 48" glue up table ready to handle my modern glue. I disagree about clamp pressure in the middle spreading ends. Not if the boards are squared properly before the fact. I double check in a dry glue up in advance see what will happen under pressure and I do have clamping power in the Cabinet-masters.

Look at this picture of a crochet lamp table top. Click on pic to enlarge. It is made from 4 glued boards. See if you can even tell where the glue lines are on the glued pieces. In almost 40 years I have never had an end open yet using both a spring joint until around 1994 and my currect technique of dead on mesh before the glue. And.. I don't expect to for that matter as in both methods I understood the limits of what I was working with at the time.

[Hank Knight]

I would like to add a comment about springing a joint by "taking a few swipes with a hand plane." I have found that introducing a slight hollow in an edge joint is easier with a hand plane than with a power jointer (with which I have had little success). But poor technique with the hand plane will ruin the joint.

First, I don't agree with using a jointer plane for this task. The purpose of the jointer plane is to rid the surface of high spots and hollows, not introduce them. Unless you're working a very long edge, it's easier to introduce a hollow with a shorter plane like a jack or even a #4 for shorter work.

Second and most important, regardless of the plane you use, it is imperative that you end up with a perfectly square edge. If you start with a square edge from your jointer, you need to take a perfectly even shaving across the width of the cut with the hand plane so the resulting edge remains square, albeit slightly concaved. If the sprung edge is not square it will not mate perfectly with the opposing edge when you apply the clamping pressure. The result will be a substantially weakened joint. This takes a little practice. I still check as I go with a small square and adjust the cut as necessary to achieve a square ege. I like to finish up with one final end-to-end pass to smooth out the trasnition between the springing cuts and the original edge, leaving a continuous, slightly hollowed, square edge for the glue surface.

Having said this, I agree with Pat Warner and others who advocate for a straight, square, perfectly mated joint rather than a sprung joint. If you start with dry stock and use modern glues, there is no need to spring an edge joint, especially if the finished piece will live in a modern climate controlled environment with only modest humidity swings.

My $.02.

Hank

[Rob Woodman]

I bet George Ellis though he was finally settling the argument on this practice once and for all...



No, he was informing future generations of carpenters and joiners of the best practice of his time, something that is still of value when trying to restore buildings over 100 years old.

Regards Rob.

[Rob Woodman]

"Modern Practical Joinery" published in 1902! haha.. Mr. Ellis was working with Hide glue in those days and 1902 clamping systems. "We've come a long way, baby" as the expression goes with both glue technology and clamping technology. The glue I used when I started in 1972 and the clamps were far from what I have availble in my shop today so I used a spring joint at that time.

Which is why I wrote word for word what appears in this book.;)


As already mentioned I don't after I learned proper set-up and technique on a jointer and working with far superior clamps and glue. I have 14 Jorgy Cabinet-masters setting on a 60" x 48" glue up table ready to handle my modern glue. I disagree about clamp pressure in the middle spreading ends. Not if the boards are squared properly before the fact. I double check in a dry glue up in advance see what will happen under pressure and I do have clamping power in the Cabinet-masters.

The technique at the time was to do a rubbed joint, then hold it in place with cleats and wedges, these are not a great clamping technique as the wedges would be driven with care so as not to dislodge the joint already formed.

Regards Rob.

[Craig White]

What kind of jointer are you using?

The Porter has a star knob on the infeed table that selects a spring joint or a straight joint. You can just make it out in the picture.

http://i843.photobucket.com/albums/zz360/craigwhitefurnituremaker/springjointselector.jpg

The Moak doesn't have that feature.

http://i843.photobucket.com/albums/zz360/craigwhitefurnituremaker/moakjointer.jpg

Some of the Oliver jointers have similar capabilities.

[George Clark]

Dru,

I'm not going to comment the value or lack thereof of the spring joint, but I would like to offer the technique I was taught to make the joint. Use a jointer plane set to take a very fine shaving. Start the cut a few inches from the end of the board and lift the plane the same distance from the opposite end of the board. In a very few passes the plane will quit cutting, a very slight hollow has been created and you are done. I think it goes without saying, your cuts need to be square to the face of the board.

As for the remarks about hide glue, some of the finest chair makers in the country still use hide glue to assemble their chairs and it doesn't have anything at all to do with tradition. They have simply determined through experimentation and destructive testing that it is still the best glue available for their application.

George

[John Thompson]

Dru,

As for the remarks about hide glue, some of the finest chair makers in the country still use hide glue to assemble their chairs and it doesn't have anything at all to do with tradition. They have simply determined through experimentation and destructive testing that it is still the best glue available for their application.

George

I wasn't knocking Hide Glue George. As you know not only chair-makers but many of the finer luthiers use it also. It will hold up for very long periods (centuries in many examples) when mixed and used correctly. And even if a joint fails it is by far the easiest glue there is to flush out for repair work as simple hot water works. But... in order for it to do it's thing properly the joinery must be extremely good or specific adhesion will not occur IMO. I won't go into electro chemical attractions between molecules as the main theme here is how to produce a spring joint and if it is worthwhile.

So you are so correct that hide glue has been proven over time. What I referred to about the glue I used back in the early 70's being inferior to today's glue was standard white or carpenters glue. The vast majority of amateurs used it as it was quick and simple. I doubt seriously if many will jump on board the hide glue train even once they understand it has passed the test of time due to the fact they would deem it too complicated. Nor do I believe that the majority which are amateurs and many new ones at that can produce joinery adequate to compliment Hide glue. It is of my opinion that for the most part it will remain in the hands of professionals such as chair-makers.. luthiers and those as Ray Pine in VA. that repair period pieces for a living. Just my opinion of course.

On a side note the modern glues are strong but.. who knows how they will hold up over time at this point? That question has already been answered on Hide glue as all the precincts are basically in and accounted for.. Bottom line.. Hide glue is fantastic.... in the right hands! :)

Regards...

[Frank Drew]

I'm extremely reluctant to take issue with anything George Ellis said, but IMO a rub joint isn't the best match with a sprung joint. Particularly with quick-grabbing hot glue (hide glue), a rub joint between two intimately matched edges (no gaps) is strong enough not to need further clamping, although in practice, and working alone, I'd only feel comfortable doing this with shorter lengths, maybe up to 24-36".

If the joint is sprung, on the other hand, rubbing it won't create maximum grip because the middle of the boards aren't as close as they need to be, and you'd better get the clamps on ASAP to close up that middle before the glue chills and loses its tack.

The thinking behind sprung joints is that boards lose more moisture through their ends than through the middle, so, with the slight shrinkage and resulting loss of tension that comes with that moisture loss, a sprung joint will eventually relax into a straight edged joint.