Method of joining timber

[Arron]

Today I was thinking about joining timber. I have recently been making a small cabinet out of 'plank joinery'. This is where the carcase is simply flat boards, joined together. This post is the general idea - I did these a while ago using dovetails, but they illustrate the point, you are effectively joining the endgrain edge of one surface to the very end of a longgrain surface http://www.woodworkforums.ubeaut.com.au/showthread.php?t=7664&highlight=arron+jarrah. I was thinking about the various ways of doing this type of joint:

1. dovetails. OK in most cases but in this case would not suit the style.
2. mitered corners, perhaps with key. A pain to cut accurately without specialised equipment, and style would not suit.
3. biscuits. OK, but create a weakness on the residual timber on the outside of the biscuit slot
4. dowels. OK
5. M&T. Not practical. Same problem as biscuits but worse.

I eventually decided on using dowels. It worked, but dowels are demeted. I wont go into them here, but there are a lot of reasons why I just dont like them. So I was thinking - if the following things are true:
1. modern glues are more then strong enough, if used correctly, to hold indefinitely without any mechanical support.
2. end grain effectively cannot be glued.
3. if two surfaces are flush-glued, and the glue does fail, then it does so neatly and without damage, and can simply be reglued.
4. the expansion/contraction of small section components is insignificant and can effectively be discounted.

then why not use the following method.
1. along the endgrain surface, route a groove (dado) about 15mm deep, and as wide and long as the component will allow without damage. Say for 19mm stock, route a groove 15mm deep by 15mm wide and stopping 20mm short of the full width of the board.
2. cut a 15 x 15mm strip of timber, the same length as the groove.
3. glue the strip into the groove.
4. after it is dry, plane it down till the surfaces are flush and the end quite square.
5. glue the two boards together. The endgrain has effectively been replaced with long grain, so it should hold.

the picture shows what I am meaning.
do you think it would work ?

ps. sorry if this idea is already well known, or it is someone else in this forum's - just havent come across it myself.

Arron

[echnidna]

The grain of the loose tenon should run the same direction as the boards you are joining together. Crossgrain gluing that you describe can deteriorate over time due to differentials in the timber expansion.

[Wongo]

2 things Arron,

1.How strong do you want and why
2.I don’t think your joint is stronger then a M&T joint. The strength of your joint is purely the strength of the bond. A tenon in a mortise with glue has to be much stronger.

[mat]

IMHO your reason not to use biscuits doesn't hold. The weakness you describe is really insignificant.

[underused]

IMHO your reason not to use biscuits doesn't hold. The weakness you describe is really insignificant.

I think I have to agree with Mat. People have been using biscuits for years in the making of furniture, without too many problems. Not perfect I admit (as I learnt from the WWchannel recently:D), but for ease of use and end result its not a bad option.
Cheers. Gary.

[silentC]

Which way does the grain in your inserted strip run?

[Lignum]

The grain of the loose tenon should run the same direction as the boards you are joining together. Crossgrain gluing that you describe can deteriorate over time due to differentials in the timber expansion.

Exactly, and that is the same reason dowells dont work, because who alignes the orentation of each individual dowel when their flat out in the middle of a glue up?

If you made the top an extra 35mm long and cross-cut 15mm of each end, you could in theory use that as the inlayed tennon, at least that way all the timber would be moving together. Im not sure how long it would last or if strength over time would hold but its an interesting idea:)

[Ashore]

If you are having problems with dowels try the ozzie dowel jig
http://www.ozziejigs.com.au/
Works for me with great accuracy and ease


Rgds

[Arron]

Pleased to see so many responses so soon - it seems I'm not the only one taking it easy at work today. I would like to respond to some of these.

Echidna - I think you are dead right. I forgot about that issue. Thanks. Leaves me feeling a bit stupid, though.
SilentC - it would run across the board. I think you are onto the same thing as Echidna.

Wongo. I think there are a lot of myths about M&T. I also think it has been adequately proven that the mechanical properties (ie a thing in a close fitting hole) adds very little strength in the long term - the strength comes from the fact that the M&T exposes fairly large long-grain gluing surfaces. However, the surfaces exposed are much less then in my idea. In any case, the problem with M&T in this particular situation is that the mortise is very shallow and very close to the edge of the material, having a wall thickness of only a couple of mms of endgrain.

Mat and Underused. I used to be a big fan of biscuits, and used them exclusively for the first couple of years I was into this hobby. Most have stood up well, except where the biscuit was very close to the edge. In that situation the component breaks away pretty easy. Worse still is the tendancy for the thin wall to break away before the component is glued up, say when trial fitting. It is also worth noting that in this case you are still gluing endgrain to longgrain - the endgrain of the stock to the longgrain of the biscuit.

Lignum. I agree about dowels. The key point here is that if the boards are 16mm thick then the dowel will only penetrate about 12mm. Four or so dowels penetrating 12mm is not much holding surface.

Still, I think Echidna has killed the idea.
Arron

[silentC]

Half blind or full blind dovetails might do it for you if you don't want to see them.

[echnidna]

It isnt hard to run the grain correctly even if the tenon is only 15mm along the grain.
OR
You could always make some special biscuits from solid timber with the grain running along the board axis. That way everything is long grain to long grain.

[JDarvall]

I think you'd definetly should stick with a mechanically strong joint.....I think your idea is insteresting, but to me, glue just on itself seems too weak even if you align the grains well.

What you've got there is a classic carcass joint situation isn't it ? ..... To me , that means a few dovetails or fingers to ensure it stays locked....which means if you want them hidden makes me think of half and blind dovetails like Silent said, I reakon.

oh, there's dowel, but you don't like them.......I think they can work quite well if use them in multitudes... I mean, not just 2. Maybe 8 ? ....and small ones, to get that distance between them and the edge as far apart as possible. Probably be a lot faster than blind dovetailing ?? Personally not keen on the look though. Which tends to be uno, a long edge of exposed end grain.

anycase:)

[Rocker]

Arron,

I think you are overestimating the difficulty of making biscuit-reinforced mitre joints. All you need is a crosscut sled like this one to cut the mitres, and a biscuit joiner capable of cutting a slot accurately on a mitre face. I have made two cabinets recently using this joinery and they worked fine, with or without dovetail keys, if they are glued with an epoxy like Techniglue. See http://www.woodworkforums.ubeaut.com.au/showthread.php?t=19575 .

Rocker

[niki]

Arron

Please Have a look at the picture, I made this unit in Japan some 7~8 years ago.
The unit was transferred from Japan to Israel and than, to Poland.
Made with biscuits, not the normal ones but “hand made” from plywood.
The unit is still standing without any signs of fatigue.

That was before I made a doweling jig (I will post it soon), since than I’m working with dowels, much faster and simple than biscuits, at list for me.

niki

[Harry72]

Why not just use a mitre join with a full length spline?(biscuit on steroids...)

[zenwood]

I agree with Harry: if you don't wan't dovetails or fingers, spline reinforced mitres are very strong, and quite easy to cut, especially compared to full-blind (secret) dovetails. They can run "longitudinally" if you don't want to see them (as per Harry's post), or you can cut a series of transverse slots and fill these with splines that are cut so their grain runs perpendicular to the mitre.

As an example, see my zigzag side tables (http://www.woodworkforums.ubeaut.com.au/showthread.php?t=25114), whose strength is demonstrated here (http://www.woodworkforums.ubeaut.com.au/showpost.php?p=247673&postcount=20):

http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=17452&d=1136720006

I'd thoroughly recommend the Ozziejig for dowell joinery too.

I think your original proposal with the inserted piece suffers no matter which way the grain is aligned: (1) if lengthways, then differential expansion will destroy the joint between the insert and the piece it is inserted into, and (2) if cross-ways, then there is no long-grain to long-grain glue surface between the insert and the piece it is inserted into, leading to a very weak joint.

[mat]

The concept of cross grain gluing vs strength is interesting as M&T joints are usually grain running at 90 degrees.

[silentC]

Yes but it is a relatively small area. The wider the area, the more seasonal movement there is, given that each fibre expands or contracts by the same amount.

[soundman]

have you considered the various machined joints.
simple rebates
rebates with interlocking toungues
various lock mitre joints.

finger joints perhaps

cheers

[Arron]

Thanks for the replies guys. I can see my idea wouldnt work. I'd like to respond to some comments put forward.

Rocker (and Zenwood) I think you are probably right that a mitred joint is best, and avoids the visible endgrain - except that I dont have a table saw that will do a straight crosscut. I have relied upon cutting things near enough and then cleaning up and squaring off the cut with darkside methods. Darkside shaping accurate mitres along a long edge and then getting a gap free joint looks a bit out of my league - especially when it is endgrain being planed. Perhaps I should buy a better tablesaw. I actually didnt realise most of you guys had gear like that.

Niki. By the looks of your photo, the boards you are joining are about 40mm thick. Mine are 15mm thick, so the outside wall of the biscuit slot is about 5mm - of crumby 60 year old oak. Also, the outside wall is endgrain, so has zero strength of its own. I think that difference is significant. Even after drilling the dowell holes, three of them broke away across the wall during trial fitting.

Apricotman. I'm afraid I'm going to have to disagree with you again. My contention is that M&T have negligable mechanical properties and work because they expose a large gluing surface. I guess the proof would be to make a chair with M&T joints and assemble it without glue, use it and see how long it lasts. I think glue is sufficient to hold a joint where your application meets all of its prerequisites. The major prerequisite is a large gluing surface, so thats why contrivances like M&T are employed. (obviously things like pinned or wedged m&T are a different case).

Where this prerequisite is met - such as when laminating boards for a table top, I'm sure most of us have found that well shaped boards can simply be edge-glued. My idea was an attempt to maximise surface area, to the point where it met the prerequisite, and do away with the contrivences.

cheers
Arron

[Lignum]

Arron, cut the boards slightly over size and ring up the closest joinery to you and ask if they will quickly cut a few 45`s on them. They will only be to happy even happier if you offer them a slab of premium beer for their effort:)

[silentC]

My contention is that M&T have negligable mechanical properties
I think negligible is a bit of a strong term here. There are plenty of M&T joints in solid wood construction that do not use glue. An integral tenon (as opposed to a loose one) in a tight fitting mortice can tolerate sheer forces. They don't do so well in a racking situation (such as a chair leg joint) but neither do most of the joints used in that situation once the glue breaks down. It's not one of the most, if not the most, popular joint for nothing. Your situation doesn't call for one though.

[JDarvall]

Apricotman. I'm afraid I'm going to have to disagree with you again. My contention is that M&T have negligable mechanical properties and work because they expose a large gluing surface. I guess the proof would be to make a chair with M&T joints and assemble it without glue, use it and see how long it lasts. I think glue is sufficient to hold a joint where your application meets all of its prerequisites. The major prerequisite is a large gluing surface, so thats why contrivances like M&T are employed. (obviously things like pinned or wedged m&T are a different case).


uno, I don't really have any proof. I've only got a few feelings on it, which may make my opinion look a little simplistic.

The idea for me when deciding on a joint, is to ensure its mechanically sound,....the thought being.....' I want the joint to survive when the glue starts to fail ' .....I look it at a little differently I suppose. But, I admit, it could be totally wrong.

Mechanically sound for me includes the tension created by a tight joint. To me its like, lacing your fingers tightly(like the tension of a tight dovetail joint), then getting someone to pull your hands apart. There's obvious resistance. And then comparing that with just holding your hands together and getting someone to pull them apart.....well you just can't stop it from happening <- this last one relates to the glued only butt joint your talking about, IMO.

Also, there must be other important qualitys with a mechanically sound joint, regarding resistance to twist etc, which I'd say is very important too in furniture. Twist is something a simple butt joint would have trouble dealing with I'd imagine. Once the joint gets weaken from a bit too much twist, game over probably.

The whole thing sounds like a complicated study. Probably somebodies already done a study on it. Maybe we could source that from somewhere.

But concerning your idea on inlaying a strip of timber into the endgrain, so that you get a good long grain grip. ........ you may manage to get a strong enough bond there, but what about the bond between the strip and its groove ? Would that be strong enough ? Isn't that End grain on long grain ? Maybe epoxy would make it work.

Again I don't really know. Sounds like its worth a test. In anycase, I enjoy thinking about this sort of stuff. Thanks for the thread.

[Arron]

Mechanically sound for me includes the tension created by a tight joint. To me its like, lacing your fingers tightly(like the tension of a tight dovetail joint), then getting someone to pull your hands apart. There's obvious resistance. And then comparing that with just holding your hands together and getting someone to pull them apart.....well you just can't stop it from happening <- this last one relates to the glued only butt joint your talking about, IMO.

The problem I find with the mechanical advantage provided by a very close fit is that it breaks down pretty quickly. You've probably heard the saying that a good dovetail (or m&t) only goes together properly once. Push it together and wiggle it apart a few times - as we often do during dry fitting - and its already starting to look a bit weak. In the real life of, say, a chair then these twisting forces are being exerted by every postural adjustment of the person sitting in it. Eventually they all wear away at the tightness of the fit.

SilentC. I am interested in the idea of an M&T joint that doesnt need glue. I assume they all have some type of integral lock or pinning strategy - which takes the place of glue.

regards
Arron

[silentC]

One example is a breadboard end. You don't glue them. Others include frame parts in a cabinet where a dry fitted tenon is housed in a mortise but not glued so that it can move in and out. It must still support weight. The use of a mortice and tenon in these cases must provide some strength, otherwise, why use them?

[Arron]

But concerning your idea on inlaying a strip of timber into the endgrain, so that you get a good long grain grip. ........ you may manage to get a strong enough bond there, but what about the bond between the strip and its groove ? Would that be strong enough ? Isn't that End grain on long grain ? Maybe epoxy would make it work.


Sorry, forgot to address this point. As Zenwood and others have pointed out.
Yes, if you cut the strip along the grain, then it would be glued into its dado with no problem but the glue bond to the other board would not be long lasting (grain directions at 90deg, hence expansion and contraction differential).

But, if you cut the strip across the grain, it would glue well to the other board but could not be reliably glued into its dado (most of the contact all round includes at least one side being endgrain).

Funny stuff, wood.

Arron

[Arron]

One example is a breadboard end. You don't glue them. Others include frame parts in a cabinet where a dry fitted tenon is housed in a mortise but not glued so that it can move in and out. It must still support weight. The use of a mortice and tenon in these cases must provide some strength, otherwise, why use them?

How did you get to answer my question before I answered it ?

The breadboard is pinned at some point, is it not ? If not, it would pop off fairly quickly.
The other example, well its not fixed at all, so I dont see how it can demonstrate the strength of a bond.

regards
Arron

[silentC]

I can see this heading into a debate on semantics.

Yes, the breadboard is pinned, else it would pop off as you say. However it is the strength of the tenon in it's mortice which prevents the boards from cupping, not the pin. When it comes to being able to pull a tenon out of it's mortice, you are correct, without glue or a pin or wedge, it will pop right out. However, in other directions of movement, a M/T has strength in it's own right which does not rely on glue.

There are very few joints that cannot be pulled apart the same way they were put together if glue is not used. The only one I can think of off-hand is the foxtail wedged tenon which cannot be separated once put together.

[JDarvall]

. In the real life of, say, a chair then these twisting forces are being exerted by every postural adjustment of the person sitting in it. Eventually they all wear away at the tightness of the fit.


Yep, I can see your point. But all joints would wear in one way or another wouldn't they. I suppose its a question that can only be answered by a test.

I don't mean to look stubborn, but to me it stands to reason, that the deeper mechanically locking a joint is , in general at least, the greater the strength. So where does that leave a butt joint. ..... I find that hard to dismiss. Really feel you've got to have something more to relie on than a just a good long grain glue joint.

But I hope your right. You never know. Maybe you've clued onto a sound method of joinery. lots of tests are needed I think.....

[Auld Bassoon]

There are very few joints that cannot be pulled apart the same way they were put together if glue is not used. The only one I can think of off-hand is the foxtail wedged tenon which cannot be separated once put together.

SilentC: is the foxtail wedged tenon you refer to like a sliding dovetail that is cut in two down the channel, the 'tenon' part of the dovvie inserted, and the two cur parts glued together again?

[silentC]

No it's a standard tenon but you cut a couple of slots in the end and put in some wedges then you push the whole thing into a blind mortice. When the wedges contact the bottom of the mortice, the wedges are forced into the slots in the tenon and this locks the joint together as it would for a wedged through mortice. It's probably a very difficult thing to make because everything has to be just right and you only get one shot at it.

[zenwood]

Tusk tenons and other wedged tenons are held in place without glue. If they work loose, a tap on the wedge tightens them up again.

http://tomecat.com/jeffy/ww/projects/video/tusk.jpg

http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=11011&d=1122426333

BTW Another term is "fox wedged tenon":

http://www.ilovewood.com/foxwedge.jpg

[JDarvall]

I like the look of that exposed fox tennon, Zenwood.

[Ticky]

Arron, cut the boards slightly over size and ring up the closest joinery to you and ask if they will quickly cut a few 45`s on them. They will only be to happy even happier if you offer them a slab of premium beer for their effort:)

I think Lignum is on the right track if you want to rely on glue instead of any mechanical joint. I believe there is a joint called a scalf joint used in boat building to join planks, where the planks are laid back to back & a very shallow angle is cut throught the 2 planks at the same time. When the top plank is flipped over, the 2 angles =180 degrees.

This method would give you a longer joint than a 45 degree cut, giving you a larger glue surface area & a more or less long grian to long grain joint. This would also be better as you don't need to be so acurate, a problem you noted earlier.

Steve
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[zenwood]

there is a joint called a scalf joint used in boat building
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</td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td><td style="border: medium none rgb(224, 223, 227); 42pt; background-color: transparent;" width="56"></td></tr><tr style=" 13.5pt;" height="18"><td style="border: medium none rgb(224, 223, 227); 13.5pt; background-color: transparent;" height="18"></td><td class="xl22" style="border-style: solid none solid solid; border-color: windowtext rgb(224, 223, 227) windowtext windowtext; border- 1pt medium 1pt 1pt; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl23" style="border-style: solid none; border-color: windowtext rgb(224, 223, 227); border- 1pt medium; background-color: transparent;"></td><td class="xl24" style="border-style: solid solid solid none; border-color: windowtext windowtext windowtext rgb(224, 223, 227); border- 1pt 1pt 1pt medium; background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td></tr><tr style=" 12.75pt;" height="17"><td style="border: medium none rgb(224, 223, 227); 12.75pt; background-color: transparent;" height="17"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td><td style="border: medium none rgb(224, 223, 227); background-color: transparent;"></td></tr></tbody></table> That would be a "scarf" joint, I believe, used for lengthening a workpiece. Simple versions are straight cut at a shallow angle, or they can be more complicated, like this notched, tabled and wedged version, starting to look like a japanese puzzle:

http://www.htf.ab.ca/images/build1/Image7.gif.

No good for Arron's 90 degree joint, though.

[Ticky]

That would be a "scarf" joint, I believe, used for lengthening a workpiece. Simple versions are straight cut at a shallow angle, or they can be more complicated, like this notched, tabled and wedged version, starting to look like a japanese puzzle:

No good for Arron's 90 degree joint, though.

Zen, you are correct, No good for Arron's 90 degree joint. I didn't look at the pic, & I had it in my head that Arron was trying to lengthen his boards.:o Interesting post though, I had never heard of a Fox Tail joint before, & I also learnt more about scarf joints than I knew before.

One thing makes me wonder however, Arron was reluctant to use a M&T for reasons of strength, yet removing material & replacing it with other material seem almost the same to me, as a M&T, at least on one side of the joint.

Having made my mistake, I still think Lignums 45degree angles or as someone else said, a lock mitre joint would provide a larger glue surface area and reduce the effect of an End Grain.

steve

[Lignum]

If you get someone else to cut the 45deg, you just have to use your bisc jointer to cut some slots for biscuits, or run the jointer down the majority of the mitre to fit a spline. Just stop it 20mm in from the ends. Simple solution to a simple prob:)

[Jedo_03]

Arron,

I think you are overestimating the difficulty of making biscuit-reinforced mitre joints. All you need is a crosscut sled like this one to cut the mitres, and a biscuit joiner capable of cutting a slot accurately on a mitre face. I have made two cabinets recently using this joinery and they worked fine, with or without dovetail keys, if they are glued with an epoxy like Techniglue. See http://www.woodworkforums.ubeaut.com.au/showthread.php?t=19575 .

Rocker

Hey Rocker - and all...
Is it poss to make a crosscut / mitre sled like this that would "fit" onto a MK3 Triton - or is there a better idea?
Seems to me the "groove" on the Triton MK3 may not be very accurate.
Thanks
Jedo

[Rocker]

Jedo,

I have never owned a Triton setup; so I can't give you a definitive answer. But maybe you have reached the point that most Tritoneers seem arrive at after a few years - that it is time to upgrade to a real table saw. If you have not reached that point, it might be best to avoid mitre joinery:)

Rocker

[Jedo_03]

Thanks Rocker
Yer dead right there. . .
Soon as I win the lotto...
Jedo