Hi, I’m making two replacement doors with glass for a small cabinet. The original doors were T&G but I’m in a hurry and came up with this. Doors are 13 X 20 out of 2¼” oak.
Porter Cable FF biscuts, doubled and I’ll route out for the glass later.
Will the joints hold?
Replies
The two biscuits side by side in relatively thin material will not be as strong as a single biscuit in the same material. The biscuits are made of Beech and are not as strong as the door material. You are sacrificing native material glue surface for inferior material glue surface.
With that said, do not scrap what you have already done. I would recommend using only a single FF biscuit in the future.
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Michael in San Jose
"In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted." Bertrand Russell
Interesting take, I thought using two biscuts would be increase the gluing surface and stop the joint from twisting. You say it is weaker.
I'll have to do a mock-up and smash it.
Thanks
I think.
I disagree with MichaelP. I like the idea of using two biscuits in the stock you pictured, mainly because the door will have less tendency to rack.
Will they hold? Absolutely -- maybe not quite as strong as a mortise/tenon, but better than a cope/stick joint.
I would consider using a floating tenon. The mortice can be the same outline as the slots that are there, just deeper and a lot stronger with a hardwood tenon. It shouldn't take long to do, either.
"I cut this piece four times and it's still too short."
Thanks highfigh. I was going for speed and hopefully strength.
Fingers crossed, I deliver tomorrow.
Another thing you could do that only requires one cut per joint is a spline. You could use the same kind of wood or a complimentary one. If your table saw blade has alternate tooth bevel, you would want to flatten the groove bottom, but other than that, I don't think it would take very long. If you decide not to do it for this project, it's something you could use in the future.
"I cut this piece four times and it's still too short."
Forgive my ignorance. A cope/ stick joint is the common panel door joint?
<<"A cope/ stick joint is the common panel door joint?">>Yes.
If you aren't willing to bridle or M&T it then that is your best bet. In that case two is absolutely better than one. Because of the end grain the butted surfaces are worthless as far as glueing goes. In fact if the origional T&G was small this might be stronger.
Mike
Gordsco,
I'm a little late coming in here, but I have to comment on this joint. You are really asking for trouble. There's a very good reason that the original workmanship used a M&T joint - its strength. There is no strength added to a joint by biscuits. Like dowels, their most useful function is for alignment. That's the reason they were developed originally. Yet they have gained enormous popularity, all for the wrong reasons. I'll never understand why so many workers have embraced this technology, almost to the complete exclusion of understanding joint anatomy and the requirements of proper long-grain to long-grain mating (whether oriented in the same direction or crossed at 90 degrees).
While they may have a little more strength than a similarly doweled joint, that's about it. The joint will hold for a little while when new, but will eventually fail as the joint is basically end grain to long grain joint with some of the joint surface taken up by the biscuits. They are NOT splines, just because they look like they MIGHT be.
Many joints will outlive you in this application if competently done (M&T, splined ("floating") M&T, bridle). But the design you picture is a very poor one.
Rich
The joint will hold for a little while when new, but will eventually fail as the joint is basically end grain to long grain joint with some of the joint surface taken up by the biscuits. They are NOT splines, just because they look like they MIGHT be.
'have to admit i don't understand this. Aren't the biscuits in fact splines, albeit small ones? Ahd they yield long-grain-to-long-grain glueing (i.e., from stile to biscuit, and also from biscuit to rail), which gives the joint almost all its strength.
Since the glue surface area of the bisuits are so small, the joint isn't as strong as those with larger long-grain-to-long-grain contact, but hey, at least it's not pocket screws.
Barry
On a good day I can break a FF biscuit in my hands. They do not add strength, and two of them as portrayed above add less strength. The biscuit is a lesser material compared to the two pieces being joined.
A cope and stick joint is stronger because it gives you more wetted surface of the same material. A spline joint is stronger because it is binding two pieces with the same material, much as a M&T joint. A M&T joint, and a spline joint bind similar materials in a cross grain manner adding strength._________________________________
Michael in San Jose
"In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted." Bertrand Russell
The biscuits are stronger than a butt joint because there is material to resist the tension on the joint when something tries to rack the joint, but the commonly used biscuits are pretty weak. I have seen plastic and metal "biscuits", but I don't think I would use them for anything like a door with glass. If solid material was used (poplar would be better than the thin, stamped plywood used currently), the joint would be considerably stronger as long as the grain was oriented properly. Personally, I think the biscuits could be thicker. They're OK for a face frame when it has dados with the sides, top and bottom of the box inserted and glued, but a door with glass puts more stresses on the joints. Pocket screws are pretty common now and they are a quick way to put the frames together. Nothing particularly resembling craftsmanship like a cope and stick or M&T, but they work. A haunched tenon would probably be the strongest joint, but this door isn't very large."I cut this piece four times and it's still too short."
Edited 11/28/2004 6:12 am ET by highfigh
Barry,No they are not pocket screws. But why even entertain them? A screw (or 2) driven straight into the joint through the vertical member into the end grain of the horizontal member will give better service than the biscuit joint. Just sink the screw head a little and apply wood putty or a plug.You're simply not accepting the reality of the strength potential of the biscuit material, its mechanical characteristics and the needs of a joint for strength. Or you haven't had enough experience with biscuits to understand their uses and limitations. While they are "splines" by their position in the joint, they are not strength-giving members at all.The buscuit technique was developed by Lamello over 30 years ago as an expedient method of aligning boards to be glued edge to edge. The technique was (is) superior to using dowels for alignment as the biscuit could slide slightly in the prepared slot with no loss of alignemnt accuracy. The biscuit was also allowed thickness slop in its slot as it was designed to swell with absorption of water when glue was applied, resulting in perfectly aligned boards. It's a pretty impressive technology for its intended purpose.Biscuits have their own sets of problems, however. Chief of which is the tendancy to telegraph their presence to the face of the boards. The combination of their swelling and water from the glue can raise a biscuit shaped mound on the face. It will go away if the joint is allowed to stabilize for a while (sometimes weeks). But if you plane or sand it right away (a BIG temptation for the typical biscuit joint fan) it will eventuall sink below the face surface, leaving an ugly hollow that can't be repaired well, if at all.Dowels, on the other hand have to be drilled very accurately and can cause a lot of problems in assembly and glue-up if one is out of line. Time is money in the furniture business.An edge glued panel of boards has greater strength at the glue line(s) than the wood itself. The biscuits do not add any strength in there. They actually weaken the joint(s) by a miniscule amount because they take up some potential long grain to long grain contact area. So they must be used sparingly.But just like with dowels, a lot of woodworkers have misunderstood a technology from the furniture industry and assumed that these devices are the way that joints are to be made and have embraced them wildly. Who hasn't seen furniture advertised to be strong because its joints are dowelled? (NOT!)Except for use to draw a M&T joint together by being driven into slightly offset holes, a dowel NEVER adds strength to any joint. I think biscuit joints have been embraced because the slot cutter is such an attractive tool. And, after all, we are all such tool freaks.Cut some quick biscuit slots into joint members, pop in those puppies and glue 'em up! Hey, I'm a furniture maker!Maybe it shows. I have no use for biscuits. And except as mentioned above, across a M&T joint (when I use square pegs), little use for dowels. Every joint that can be made in wood can be constructed quickly, once one knows the principles and the needs of the joint without these quick-assembly aids that the furniture industry must use if it is to build large quantities of goods that can be affordable.I didn't mean to go on quite this long. I recommend that if you have already glued up your frames, that you carefully add screws to reinforce the joint. Drill the screw holes as I described above, using a smaller that normal pilot drill into the endgrain portion of the joint. Good luck.Rich
It sounds like we're all trying to get the doors to last forever. A.) It won't happen and B.) They're not going to be banged around very much. If they need to be modified later, it's not going to be the end of the world. The doors can be rabbeted to accept the glass and it can be held in by toggle retainers. Go to a home center and see what they have. They're similar to what holds a mirror onto a wall (plastic piece with a screw holding it on, which can be loosened and pivoted out of the way if the glass needs to be removed or replaced). If making doors becomes a major part of the business, cutting a groove and using the flexible strip, tapped into the groove is a really common method cabinet manufacturers use to hold the glass in. If you're going to Home Depot, etc anyway, look at the kitchen cabinets for ideas. This strip comes in brown, white and translucent (not quite clear).
"I cut this piece four times and it's still too short."
"It sounds like we're all trying to get the doors to last forever."Yes, I didn't mean it to get that involved.The original question was simply, "Is this buiscuit joint acceptable? Will the joints hold?"Simple answer, No.
Unfortunately, the fatal words,"but I'm in a hurry"were also posted. In my experience people in that frame of mind never listen to the advice they seek. They never have time to do things right, but plenty of time to do them over.Interesting.Rich
In my experience people in that frame of mind never listen to the advice they seek. They never have time to do things right, but plenty of time to do them over.
You are absolutely right, (in this instance), but it doesn't mean I didn't learn something from the discussion.
I came here for knowledge and advice.
I got both
Thanks.
while this thread has probably gone on longer than need be, let me say that the double biscuit joint is MORE than strong enough for your doors.
I have built many this way, and have never had one fail. Purists or others may scoff at biscuits, but biscuits are a useful and sturdy innovation.
What has not been mentioned here is that biscuits are compressed beechwood with grain running diagonally. When glues hits it,it expands and locks into place. This is not "cheap" joinery, just another method of joinery that has it's place.
It's popular because it works. If it didn't, the market would've resigned it to the scrap heap long ago.
Edited 11/29/2004 10:25 am ET by JACKPLANE
Amen ........
Gordsco,Best of luck!Rich
If the joints fail I will certainly replace them. I thought it would be okay because they were small. As I mentioned I am in a hurry. Replacing the original doors was an oversight as of 6pm fri. and the refinished cabinet will be stained/ finished Monday.
I plan to router the back of the doors to accept the glass.
How would you fasten the glass?
I think you'll have a problem when you cut the rabbets for the glass - you may expose one side of a biscuit and you'll certainly weaken the connection since you'll have less material on one side.
Personally, I would have used a single #20 biscuit and 'cheated' it toward the front of the door (so it would be centered in the non-rabbeted part of the rail/stile).
A better solution (if you have the tools) would be pocket screws. I've used biscuits for years and never had a failure but I'm beginning to like pocket screws since you don't have to wait for glue to dry and they seem to be even stronger than biscuits. Another advantage is that you could could re-tighten pocket screws if the joint ever loosened and you would be as good as new.
All non-mechanical joints (i.e. glue only) will fail sooner or later since you're dealing with a cross grain glueup. A simple butt joint will fail first and a well made M&T will last longest. It's all about the amount of glue surface you get (and the kind of glue you use).
>>>>I think you'll have a problem when you cut the rabbets for the glass - you may expose one side of a biscuit and you'll certainly weaken the connection since you'll have less material on one side.<<<<
If you go back to the picture I posted, you'll notice I cheated the biscuts to the top of the frame to allow for the glass.
The frame is only 2¼" the slot for a #20 or #10 is outside of that, even a #0 slot is very close to 2¼" thats why I went PC mini biscut FF with an 1½" slot, I thought the joint might twist so I doubled them, thinking it was stronger. Some agree, some don't.
I glued and clamped the assembly for about 20 hours and have already sanded flush.
I'm ready to cut the rabbets.
How would you attach the glass?
I use a clear adhesive caulk to adhere the glass to the door. A small bead around the rabbet (in the corner) should be plenty. As a backup, I'll sometimes put in some glaziers points as well.
Dave,<?xml:namespace /><o:p />
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FWW did a study a while ago comparing M&T, biscuits and various other methods of joinery. What they found is that a double biscuit approach was remarkably strong compared to some other systems such as lag screws. <o:p />
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That being said, and from personal experience, double biscuits are fine for relatively low stress applications. Certainly a door would qualify; a leg to frame would be a bad idea.<o:p />
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Best of luck <o:p />
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Neil<o:p />
Neil,The article was by John D. Wagner. I can't locate the FWW issue it appeared in, but I have its reprint in Taunton's, "Practical Design, Solutions and Strategies."That article was one of the poorest studies FWW ever published. The methods used were terribly flawed and inconsistent. Unfortunately, nothing was "prooved" and the real problem is that the results continue to pop up in discussions as though they were authoratative.Among other conclusions in the article, the strength of 2-biscuit and 3-biscuit joints "tested" superior to several M&T joints in exactly the application discussed here. Surprisingly, not a shred of doubt about that result seemed to occur to the testers or the writer.It's interesting that early in the article, there is a disclaimer that, "It would be a stretch to call these tests a rigorous scientific examination," and, "a truly definitive study was far beyond the facilities and time that Taylor and Brungraber had to work with." Yet, the rest of the article proceeds as if the testing IS a rigorous scientific process with charts of force applied, breaking force, gap measurement, etc.Ironically, that same paragraph notes that, "Even within its limits, though, their work may help settle an argument or two." Unfortunately, the reputation of FWW lent an aura of authority to the article and its flawed "conclusions" have done nothing but fueled even more arguments.I don't think anyone here would have cared to champion the biscuit method as superior to a M&T joint!Rich
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