How much weight will biscuits joints hold?

allen levine

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Im about to begin a small liquor cabinet, two shelves, simple construction.
3/4 oak ply for walls, 1.5 square red oak legs.
Im not sure if I use biscuit joints if it will hold the load of two shelves full of assorted bottles.
Is there anyone who knows how much weight each biscuit will bear?(size 20)
 
No I don't but I would never trust them for any more than a few pounds. There made for alignment, not strength. I think you need to look at something more substantial. A shallow dado would be a huge improvement.
 
No I don't but I would never trust them for any more than a few pounds. There made for alignment, not strength. I think you need to look at something more substantial. A shallow dado would be a huge improvement.

Agreed.

A 1/16" dado would do way better at supporting shelf load than filling the same edge with biscuits, and it's easier to keep lined up that way, too, since you can cut the dados for both sides without changing your fence setting (just don't make sure you get yer lefts and yer rights straight, or you might have to make multiples of the cabinet!) :rofl:
 
not attempting to sound like I dont know what Im doing(its tough to hide certain facts), but I was under the impression that biscuits supply a pretty decent joint due to the swellling. I thought it was used for joints, maybe not very strong joints, but I thought a biscuit every 6 inches or so would supply sufficient strength.

I think IM not making it clear as to my design.I was going to attach the side walls to the legs, which will run from floor all the way up to top of cabinet.(about 6 inches clearance from the bottom of leg to bottom of cabinet) I was going to attach the sidewalls, along with 2 support "aprons" in the back, and a face frame in the front, then attach the bottom and upper shelf with a dado on the inner walls.
I was using the biscuits to attach the legs to the side walls, as in a table apron, I just didnt know if all that weight would turn the walls inward and not offer enough support. The bottom and the shelf will be dadoed into the side walls, so I figured alot of the cabinet strength would be in the wall attached to the legs.(ofcourse my design could be totally flawed, but I have to go with what I think and know I can handle)
 
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allen without seeing a sketch,, i am thinking you could hide a couple of screws behind your face frame to attach your legs with.. that screw shear strength is enouff for what your up to if i have understood you correctly.. if you coiuld just draw a sketch of what your up to and then scan it in to let us see your idea it wopuld help emesnsly or take a pic of your sketch wil work to.:huh:
 
asking me to draw something, hahaha.......youd have better pictures from a 4 y/o with crayons......but I drew this before I left work, measurements arent in it, figure total height around 42 inches, total width, approx 24-26 inches
Legs will extend 4-6 inches below bottom of walls.
Face frame in front will be biscuited on, then 2 or 4 doors.
Shelves dadoed in bottom of side wall, and middle. Oak ply for shelves and walls. Id screw on a 1/4 " oak ply for the back.


If I knew basic furniture construction, I wouldnt be asking.
If I was smart, Id get someone here to build it for me, but then Id have no fun messing up everything.
heres a very, very rough sketch of whats in my head.(dont know if it will help, but at least I proved how much of a beginner I am, and not too ashamed of it, cough, cough)

Now that I looked, it doesnt help that much.

I was thinking I could use something like a half lap joint between the ply and legs, cut out 3/4 of an inch on the inside of the legs, attach with glue and screws, but I dont know how oak ply would cut for a half lap joint, never tried.(I have time to think about it, I have most of the wood, but Im going to experiment with Mahogany and Cumaru, making a chair out of each, and I promised alot of chairs before the summer ends, going to make around 60 bucks a chair, not what Im doing it for, but I get egged on by my wife if Im going to build it for someone else, they want to pay, they are getting a tremendous bargain, I should just take the profit and buy myself more tools)
 

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Allen,

The guys are right. Bisquits give no strength. None. Zippo. They're just there to help you align the pieces. That's why I've put my bisquit cutter away. Couldn't find it if I wanted to... ;)

On the other hand, a long grain to long grain glue joint might just hold a good long time, if done properly. Do you have a jointer?

I've heard people criticize dadoes and half laps that are long grain to end grain, but I have the impression that argument's for purists. So far mine have always held... ;)

Thanks,

Bill
 
Allen,

The guys are right. Bisquits give no strength. None. Zippo. They're just there to help you align the pieces. ...


Can't agree with you on this Definative answer. true they add little strength in the shear factor across the biscuit bit they do serve a good alignment and lengthwise shear strength but due mainly from the adhesive along the joint. So there is some strength added by their use as well as the alignment issue.

The biscuit acts similar to ever popular Loose Tenon that is so popular these days, the strength is in the structure of the Tenon, just as with the Biscuit, so try breaking a biscuit across and lengthwise, You can snap it laterally but to shear is quite impressive. Make up a test piece and using good adhesive and given suffencient time to allow glue curing completely , snap the piece and you will fint the wood fails either side of the Biscuit, not at the buscuit, the biscuit will stay intact and the wood will fail, so where is the strength? In the adhesive and the compressed football biscuit.

I too don't use mine much but when I do it is for alignment and quick assembly but I don't discare its value, For it is just another tool in our Arsonal of Goodies.

From the sketch I would suggest that biscuts 3"-4" apart will add some stability and strength, But the effort to cut a slot and cut a mortise into the legs would be near the same and to slot the panel or cut a tenon would also be the same and a M&T panel would be VERY strong and fit your need better. And make those Biscuit Neigh-Sayers happier.
 
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Can't agree with you on this Definative answer. true they add little strength in the shear factor across the biscuit bit they do serve a good alignment and lengthwise shear strength but due mainly from the adhesive along the joint. So there is some strength added by their use as well as the alignment issue.

Bill,

So I dug a little deeper. You're right, the wood magazine test showed an end grain to end grain butt joint breaking at 139 pounds of force, and the same joint with bisquit breaking at 220. Not a big difference, but something. ;)

Here's a start for research:
http://www.google.com/search?q=Wood...s=org.mozilla:en-US:official&client=firefox-a

and an actual video of the test:

http://woodmagazine.com/jointtest

Thanks,

Bill
 
my 135 lb daughter sat on my telephone table I just finished yesterday, to test the height, it held, made with biscuits. (she wanted to tell me about how high to make her coffee table, so she sat on the table to see about how how her couch is, my heart stopped for just split second, didnt make that tiny thing for so much weight)


Im going to get a dado set, I cant continue making walls and bottoms and shelves using a handheld router, its hard for me, confusing at times, and a dado blade seems just such a simpler path to take.
I think Ill attempt to mortise the legs, can go up to 3/4 inch deep, and then I can put 2 screws, one at top and bottom, from inside, coutersunk, and it would hold the weight.I thought a half lap kinda joint between the panel and leg with a few screws would hold it just as secure, or secure enough, but I guess if Im using the dado blades, the cuts will be similar in task.
I appreciate the input.(i really love the biscuit cutter, Im sorry I wont get a chance to use it. When I got it, I told my wife I just took many years of joint learning off my list)
 
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allen there is a place for them as the guys have said,, they are great for alignment purposes and for other applications too.. its just some of the ways to do things are better than others after you learn how..
 
Bill,

...the wood magazine test showed an end grain to end grain butt joint breaking at 139 pounds of force, and the same joint with biscuit breaking at 220. Not a big difference, but something....

I'd say that is something , do the math, that is a 63% increase in strength.

I don't pay much attention to these staged fail tests (we did all them when I was in school) The wiggle and daily stress that a piece normally suffers is the real test. Also there is a point of diminishing returns where you need to factor the amount of stress you need to withstand.
 
It seems to me that most of the biscuit failures I've seen (including that one from Wood Magazine) show forces far in excess of what the joint would ever endure in the real world. Common, they (Wood Magazine) were pulling the piece being tested off the surface by quite a bit.

Add to that the fact that they used a single #0 biscuit on a miter (where I would have used two of the largest biscuits that would fit if I was concerned about strength). Compound that with the fact that biscuit failures typically occur in the biscuit itself (and plywood biscuits will fix that if you really need the extra strength).

I think biscuits get a bad rap. Very often the design of the piece (like a five-sided box) multiplies the strength of the joint (for example, the back of a shelving unit prevents racking, meaning the corner joints will undergo far less stress).

I realize that large cantilevered members where the design of the piece provides little additional support won't fair well with biscuits and therefor a M&T joint is more appropriate. But for a shelving unit or cabinet with a back, biscuits provide plenty of strength and are nice for the increase in speed with which you can build your project.

That is just my opinion.
 
this will be my first attempt to actually build something using MT joints for the weight bearing sections.
The shelves will be dadoed to the walls, so I will MT the side walls to the legs.
The back rails, one top, one bottom will be attached with glue and screws, since IM going to rabbet out 1/4 inch on the back legs, attach bottom and top rail,kinda of a half lap joint, and use 1/4 inch oak ply pinned on.
Ill build the face frame with biscuits, Ive never been able to pull the few frace frames Ive built apart, and I will attach the face frame to the inner sides of the front legs with biscuits, but will put a cleat under the bottom shelf, so it wont be seen, and a cleat up under the top of the cabinet which will be unseen due to the face frame. I believe this is something I might be able to handle, not really sure, I will practice.
I drew up neat plans today, but made a few errors in measurments, so Ill try again tomorrow, just so someone could take a quick look to make sure it looks solid enough, as I believe it will be.(or hope so)
If it fails, or I fail, Ill just be out the cost of some 6/4 oak and a small piece of 3/4 oak.(plywood would never go to waste, just trim off the tenon part)
Ive got to build a ton of adirondack chairs Ive been paid to make.
I dont want to build for profit, but people insisted, but first Ill start one out of African Mahogany, then attempt Cumaru, one of each.

Then comes the liquor cabinet.( I have the 6/4 oak sitting nicely flat on a shelf off the floor)

I want to thank those that helped me here. It speeds up the learning process, but doesnt help the skills, that will only come with many failed attempts.
 
Allen, If you are worried about how much those Licquer bottles weigh, do as I do, and never put it back on the shelf over half full....:thumb: :rofl:

Remember that they were delivered in a cardboard box so your construction should hold up well (unless you start lightening up the bottles before you are done..) :eek: :p

will be looking forward to see a finished Cabinet (complete with half empty bottles) :thumb: :rofl:
 
again, not final measurments, but basically what I think I can do.
My only concern will be the rear legs. I dont want to compromise the integrity of the rear legs with the mortise cut and rabbet cut, but I think it will be strong enough.Im not one for drawings, but this will make me understand where I want to go.
 

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I have a friend that owns and operates a furniture factory. He has used bisquets for years and has always told me that joints in solid wood will have more strength that the wood itself. His unscientific test was to construct a 90 degree joint and put pressure on it until it failed. The wood almost always failed first. I would think that properly glued joints would be plenty strong. I would think that the only issue with plywood would be if the ply soaked up the glue and caused the joint to not have enough glue to hold.
 
before I through some of the scrap pieces of cumaru lumber into the trash, I took out my biscuit cutter and TB3 glue. I know its not the best lumber to glue, but I glued it up last night, let it set overnight, then this morning when having coffee with my wife, around 7:05 am, I lifted the barbeque onto the joint, put some lumber on top of that, and a couple of jugs of carwash on that, just to see if the joints would hold.
When I went out at noontime, it was fine.
I hit the joint with a rubber mallet on the table a few whacks, then pulled it with my hands up at my chest, pulled on each end, and I only managed to get one off, I could not pull the other joint apart. This is on wood that doesnt glue well.
 

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Hi Allen.

Beware but the pressure that you put on those joints with the barbeque and the rest in your homemade test is not the total weight as the whole set is resting on the other three legs as well.

Although most part of the weight seems to be on top of the piece to test, actually is being distributed between the four standing points.

As you know already its resistance depends very much on the forces that that joint will have to withstand and in which direction will they be exerted on it. Shear, Buckling, Bending and so forth
 
Ive given up the thought of not making money selling things.
People want side tables now, and I had to knock out 4 of them today.
Its alot faster and easier using a biscuit cutter and attaching everything then using a brad gun and attaching legs to table top.
I need speed and durability.
The most weight these tiny tables hold is a corona, a bud, an iced tea, and maybe a book.
I wanted to make sure without a doubt it would hold together if someone happenned to walk along and place 50 lbs on it, or a kid sits on
gotta go deliver 3 of them.
 
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