Hi everyone,
I am planning on making some dinning chairs. I was going to make them with mortise and tenon joints until I remebered an article in FW from a few years back by John Wagner. In the article he tested M&T joints against #20 double biscuit joints and found that when pressure was applied to the joints the biscuit withstood more pounds of pressure (1600 vs 1200) before they started to gap as well as more pressure (2700 vs 2600) before complete joint failure. The saving grace for the M&T being that it had a slow failure where as the double #20 biscuit joint had a sudden, violent failure.
My question:
Are there advantages of using a more time consuming joint such as the M&T other than tradition and a more predictable failure of the joint in a worst case scenario?
Thaks to all.
kovr
Replies
Even a large biscuit will only penetrate a piece about 1/2" in it's widest part. The biscuit relies on glue alone. There are many options with a M&T joint, both in size and fastening. They can be wedged or pinned and have shoulders and haunches, they can withstand some racking during use. Fresh out of the clamps, a biscuit may be quite strong but what will happen years down the road when the glue joints have been subjected to shrinking and swelling and plenty of stress by users. Even a loose tenoned chair that wiggles can be sat in, try that with biscuits and your butt will be on the floor. Biscuits just are not in the same league with M&T, although they are a great option in some situations. I work with a lot of old furniture and the pieces that stay together don't rely on glue alone as a structural component.
Beat it to fit / Paint it to match
kovr,
Is there something wrong with tradition? Reason for tradition, in woodworking at least, is that it's proven to work, over the long haul. Traditional joinery should be a given, in a traditional design chair, in my opinion. Not necessary in a chair of original design, I suppose.
Catastrophic failure in a chair joint could end you up in court, in our litigious society.
The increased difficulty in cutting the mortise and tenon joint is balanced by ease of repair in case of joint failure. This of course should not happen in your lifetime, in a well constructed mortise and tenon jointed chair, so it might not be a factor in your decision...
On the other hand, there aren't ANY 200 yr old biscuit jointed chairs around to compare for longevity of joint integrity, so you are on your own as to how long those things will hold up under the continual stresses of use. How hard are they to replace in case of failure?
Regards,
Ray
kovr
I was lmao when I read that article suggesting that biscuits are better than M & T construction. In the last 4 years, I've been building quite a few chairs, and was taught by a 'pretty good' (laugh, he's great) chair builder. Nothing will beat the strength of a M & T joint in chairs. When I dry fit my chairs before final glue and assembly, I can sit in them with no glue! I weight 245 lbs. Try that with a biscuit!
Jeff
Oh, my cudos to Jeff Miller, my instructor!
Hey Jeff, did you take Millers' courses? If you did, how was he as an instructor? Reason I'm asking, I've heard mixed reviews.GO CUBS!!!
Georgie
I took his chairmaking class about 4 years ago, and loved it. Anybody who doesn't like his instruction is probably extremely remedial in their woodworking.
Jeff
Jeff, thanks for clearing it up. I suspected that the negative comments were biased on not understanding what he was teaching them.GO CUBS!!!
Georgie
Hope I'm not hijacking the thread, but they discussed Jeff Miller's book here, so I think I'm ok. His chairmaking course is one week long. He covers alot of material pretty quickly, because he has to. Of the 3 guys in the class with me, none were past what I would call 'beginner'. Jeff sent out a list of tools to bring to class, and these guys were taking them out of their wrappers and packages when I arrived. Jeff stresses fairing all the chair parts with a handplane, which was a difficult task for someone who never had touched one before. I finished my chair a day early, and the one other barely made it Friday afternoon with about an hour to spare. 2 had to finish at home. He stressed construction techniques, which was the reason why I took the course. We dealt with compound angle M & T construction, joint fitting, etc...
Jeff
Jeff,
I have three students now, beginers all of them. I'm holding a ten week course, building a similar sofa table to the one featured in this issue of Fine Woodworking. I'm also stressing joinery techiques, M&Ts', Biscuits, Lap joints etc. When the are done, I hope they can use their knowledge for everything from trimwork to furniture.
Next week we're meeting at Owl for wood selection! Told them to bring their Visa card!
PS...Jeff Millers' book is excellent! I don't recall him using biscuits on any joints though.GO CUBS!!!
You won't find a biscuit in his shop, unless it's got gravy on it! For his tabletop glue ups, I know he relies on the strength of the long grain to long grain strength. Biscuits really are only an alignment tool, and if you use cauls, you don't need them for that, either.
I can't think of a reason at all to use biscuits for joinery with a chair.
Jeff
P.S. I loved the Cubbie outcome this weekend, and I know you did TOO!!
Hey Jeff ,
It seems that once again we are in agreement . Could we be the only ones that feel this way ? I don't think so . Biscuits and gravy , now your talkin . I am sure biscuits have there uses although my work has never suffered from not using them . Really whatever you get used to is what we rely on as a comfort zone if you will . If others want to make beautiful furniture and biscuit joinery then more power to them . Many paths can be taken to reach a desired end result , don't you think ? I believe the pieces that we have made will be around and in good shape for many generations to enjoy . I do a lot of case work , face frame cabinetry and make a living from it . When I apprenticed we doweled all our face frames . About 25 years ago a friend pleaded with me to try pocket screws . I was convinced he was not quality oriented and knew little about fine wood working . Well I eventually made the switch to screws . The fact that they are more accurate , faster and stronger than dowels opened my eyes to new and different ways . I know many turn there noses up at pocket screws not unlike my feelings towards the biscuit , so I guess I need someone to show me data that our work would be better off with them .
dusty
dusty
I have also switched to pocket screws from biscuits for face frames on cabinetry. The only time I use the biscuits anymore is when the screwholes will be visual. I've done a few where I filled the holes with contrasting wood plugs, and they turned out nice. But, that is a visual preference that can only be made by the customer.
I don't use biscuits on my tabletops, and rely on the strength of the long grain glue joint. I have never ever ever had one split in the least amount, which makes me believe what I said earlier, alignment only.
Jeff
I've used biscuits for years. Not in chairs but in f. frames, frame-and-panel cabinet doors, and table tops. They are far more than just an alignment tool.
Biscuits are compressed beechwood with grain running diagonally, and when glued up, comprise a very strong joint. In days of yore, glues were far less strong than today, for most woodworking, so the mortise and tenon joint easily won any strength contest. All types of joints have their place; experience will let you know which one works best in any given situation.
What is the title of Jeff Miller's book? May be getting off subject a little but do you recall the title/author of any good books on rocking chair design, layout, building, that you would recommend for beginners (like me)?
kovr ,
As has been stated , the jury is still out on the longevity of biscuits especially in a critical chair joint. IMO I would consider using dowels before biscuits. If you have the time to make a chair for yourself first , then by all means give biscuits a go and decide for yourself .
2 cents worth dusty
Thanks for your thoughts. I will be going with my original plan of M&T. It never hurts to consider options but as was pointed out there is still an unknown in the long term strength for biscuits in chairs. Thanks again.
kovr,
I built 6 dinning room chairs a year ago and used Jeff Miller's “Chairmaking & Design” book for information on construction. The design I used was different than any in his book but the techniques were invaluable and adaptable to my design. The chairs used several straight, angled, and compound angled tenons. I didn't use the jig that Jeff uses in his book for cutting the tenons. I opted for the Delta tenoning jig for the table saw instead.
The book was very good and helped a great deal during design and construction.
Good luck with your project.
Dean
Pretty much agree with most of the comments on this thread except this one:"IMO I would consider using dowels before biscuits."Biscuits are not as good as M&T but they are WAY better than dowels, which have to be just about the worst joinery method I can think of. I can't even count all the chairs I've seen where the back rail separated from the back legs because the dowels failed. Dowels won't hold across grain, because there isn't enough glue surface area parallel to the long grain.The jury may still be out on biscuits, but they long ago rendered a verdict on dowels - IMO!
"Everything should be made as simple as possible, but no simpler." A. Einstein
http://www.albionworks.net
Hey AlbionWood ,
I got my start in a restoration and repairs and refinishing shop . Dowels as well as M & T were used extensively in the last 150 years or so . I am not saying M&T are not good . Both were common methods . I even repaired some interlocking M & T chairs , wow that system is interesting especially to repair . Maybe if they had biscuits they would have used them , what do you think , would they hold up ? As you said you have seen many doweled chairs with loose joints as we all have . so why did they use them so much ? Was it the level of technology available , or the cheaper furniture was doweled ?
dusty
Edited 6/25/2005 11:43 pm ET by dusty
Wasn't just the level of tech - because M&T joints predate dowels by a few centuries. So why did "they" use dowels? Not because they were better, obviously - they were faster/cheaper to mass-produce. If someone invented a machine that would accomplish the same task faster and cheaper using biscuits, you would soon see thousands of biscuited chairs. Would they hold up? Probably better than dowels but not as good as loose tenons. All three rely on glue, but loose tenons have far greater surface area so the glue bond is far stronger. Biscuits have more effective surface area than dowels, in a cross-grain joint, so I would expect them to hold up better.In handmade furniture I can't see any use for dowel joints - they are difficult to make by hand and aren't as durable as other joints that are easier to make, so why would any of us use them?"Everything should be made as simple as possible, but no simpler." A. Einstein
http://www.albionworks.net
AlbionWood ,
I don't disagree with anything you have said here . I personally do not use biscuits at all , probably only because I don't own the tool . My feeling on dowels is the main purpose is to align 2 surfaces , but they add little or no strength in most applications . When we did use dowels or M & T in chairs and tables and such , I was taught to make corner blocks and glue them in place to reinforce the corner regardless of the joinery . A stile and rail door frame with a dowels in each joint can add racking resistance especially in a man door . Many designs use either router joints or others along with screws , if done correct they seem to add strength to the joint. What has always fascinated me is the bentwood chairs originally made in France I believe , there is little or no real joinery yet they have proven to be some of the strongest chairs ever made , as well as the lightest weight . Thonet used to experiment by dropping the chairs off a roof top to test the chairs until the correct combination was achieved . Just out of curiosity when you say "handmade" do you mean with out the use of machines at all or just for the joinery ?
regards dusty
Regarding your comments on m/ts, dowels and biscuits.<!----><!---->
Years ago I worked repairing many chairs that were both doweled and tenoned. Thank goodness none were biscuited as that’s all I would have been doing.<!---->
<!----> <!---->
The problem with nearly all the chairs was not enough glue. Both M & T and dowel joints failed because holes were too deep and glue sat at the bottom unable to drive up the sides of the dowel or the tenon. What I teach my students to do with dowels is to measure the dowel, half the measurement and drill the hole 1mm deeper than the half measurement.<!---->
I also get them to cover the walls of the hole using a rounded glue stick. Glue needs to be on the shoulders of the join and the rails are glue blocked to the legs and double screwed . All hidden under the seat of course.<!---->
Emphasis needs to be on 3 major areas. 1. The fit of the dowel 2. The glue being used. and 3. The application of the glue.<!---->
<!----> <!---->
Biscuits used in chairs in <!----><!----><!---->New Zealand<!----><!---->, only ever appear in home workshops. I have never seen them used in chair making but have seen them in bed making.<!---->
Double biscuited, epoxyed, and broken! Dowel and bolt joints are better in beds for ease of dismantling and for other obvious reasons.<!---->
roo ,
Nicely said , and from experience earned on the job .
good day dusty
Biscuits should never be used where direct shear loads are encountered, e.g. chairs and especially beds, like you mentioned.
Others may disagree but biscuits have their place in other types of joinery.
We use a horizontal slot mortiser and loose tenons. Best of both worlds. It has the speed of biscuits and the strength of tenons. If you recall the article the loose tenon was right up there with the traditional M & T. Been using loose tenons for twenty years with no problems and everyone I know uses them. I think loose tenons are even stronger on angled chair joints as making a tenon at an angle allows a weaker grain condition.
rick,
"I think loose tenons are even stronger on angled chair joints as making a tenon at an angle allows a weaker grain condition."
I would think that plunging the router bit into a chair's seat rail at the seat's splay angle might weaken the rail as much as the grain on an angled tenon.
I'm not trying to pick a fight here, but it just seems to me that what strength is gained in the straight grain of a loose tenon, is lost in the short grain of the angled mortise.
I've seen only a few broken tenons in the chairs I've repaired over the years, mostly in Victorian examples, with extremely angled tenons (curved seat rails for barrel-backed chairs for instance). In repairing those pieces, It has seemed to me that in cutting into the rail to replace the broken off tenon, with what is essentially a loose tenon, that the removal of the wood at the proper angle to align tenon to mortise yields weak, short grain on one side of the "mortise" in the seat rail.
How deep into the seat rail do you typically cut the recess for the loose tenon? Do you run the slot for the tenon from top to bottom of the rail, or is the tenon haunched on top and bottom, so that it doesn't show from the outside?
Regards,
Ray
use a Mt and pin it with a hardwood dowel. That works better
Wicked Decent Woodworks
(oldest woodworking shop in NH)
Rochester NH
" If the women dont find you handsome, they should at least find you handy........yessa!"
Those biscuit joints were not end grain to long grain such as you would have on a chair were they? Chairs have always been designed so that the joint would hold even when the glue failed. I don't believe a biscuit would do that. Of course Maloof's joints defy much of the common wisdom on the subject, and he has been getting away with his little bit of magic for45 years that I know of.
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