Carcus Joints Question

Hi All
I'm starting to build my own kitchen cupboards, The base carcass's are done and I'm starting work on the upper ones. I know my dad always used a rabbet joint at the corners of the carcass's and then used a finish nails. I am wondering about using a biscuit jointer with no rabbet. Just flushing the 3/4 ply with the face out and using about 4 biscuits across the 12 inches of joint. I figure it should hold along with the glue then fire a 3 brads in there. Then I can shore it up with the face frame, if it need any after 4 biscuits.
Any thoughts on this approach.
Cheers Mike H
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The beauty to the rabbet is that it hides the end of the board. If the cut is not perfectly straight that is OK. If you butt joint with biscuits the joint line has to be perfect. Additionally the rabbet holds the joint in place perfectly during clamping. Biscuits can have a little play. I'd stick with the rabbet.
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I don't know that I'd bother with the bisquits Mike. They make alignment easier, but they don't strengthen the joint. I'd rabbit it like you Dad did, but that's just because I like the extra strength of the added glue surface. I'm not sure I'd really be comfortable with just a butt joint glued up - even with bisquits. I'd want some mechanical fastener in there. Finish nails or brads, if you have long enough ones.
--

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It's a shame this myth continues on the wreck. Many a great kitchen cabinet has been built with biscuits and they haven't fallen off the wall. If one takes time, you will learn biscuits are a wonderful tool to use in woodworking, and they easily perform structural tasks.
--
Rumpty

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Rumpty wrote:

Nobody is saying biscuits are useless, but just because the cabinet hasn't fallen off of the wall doesn't mean they strengthen the joint (depending on the joint).
Certainly a biscuited right angle joint would be stronger than a butt joint, but I'd like to hear the science of how a biscuited edge joint would be stronger than a non-biscuited edge joint.
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| | Rumpty wrote: | > >I don't know that I'd bother with the bisquits Mike. They make | alignment | > easier, but they don't strengthen the joint. | > | > It's a shame this myth continues on the wreck. Many a great kitchen | cabinet | > has been built with biscuits and they haven't fallen off the wall. | If one | > takes time, you will learn biscuits are a wonderful tool to use in | > woodworking, and they easily perform structural tasks. | | Nobody is saying biscuits are useless, but just because the cabinet | hasn't fallen off of the wall doesn't mean they strengthen the joint | (depending on the joint). | | Certainly a biscuited right angle joint would be stronger than a butt | joint, but I'd like to hear the science of how a biscuited edge joint | would be stronger than a non-biscuited edge joint. |
This may not please you, but; a biscuit seems to me to be of about the same value to a joint as a floating tenon in that it will serve to increase the glue area thereby increasing the durability and stability of the joint.
That said, the actual durability of the joint would seem to be dependant upon the quality of the glue and glue-up, and the drying time. Issue 157 of WOOD (Sept 2004) has a comparison of various glues - polyurethanes, PVA's and water-resistant PVA's. The following tests used only but joints with no additional reinforcment. All the glues tested seemed to achieve maximum strength after 30 minutes of drying time except for the polyurethanes which required 120 minutes.
When joining edge grain to edge grain, almost all the glues tried resulted in the wood failing before the glued joint. The pressure required to "break" the joint exceeded 1600 PSI in all cases. In this instance, a tenon of any variety would seem superfluous.
When gluing edge grain to end grain, the results are quite different. The use of a tenon/biscuit, dowels, cope and stick is highly recommended.
The polyurethane glues failed between 350PSI and 800PSI, the water-resistant PVA's failed between 1200PSI and 1800PSI, and the PVS'a failed between 1150 PSI and 1400PSI. Of note is the fact that 4 glues surpassed all others in this area (the wood failed before the glue). These glues are: Elmer's Carpenter's ProBond Interior/Exterior Titebond Moulding and Trim Loctite Professional Wood Worx Elmer's Probond Interior -- PDQ
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snipped-for-privacy@here.inv says...

joint a lot easier than I can break a floating tenon 1/4" or 3/8" thick.
However, to be fair, I don't know if that kind of strength is required.
--
Homo sapiens is a goal, not a description

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If you can "break a biscuit across a joint easier than a tenon", then I would suggest you are using the wrong quality of glue. Read the rest of my reply of which you cited only a part.
--
PDQ --
| > This may not please you, but; a biscuit seems to me to be of about the = | > same value to a joint as a floating tenon in that it will serve to = | > increase the glue area thereby increasing the durability and stability = | > of the joint. | > | But not the equivalent in strength. I can break a biscuit across a | joint a lot easier than I can break a floating tenon 1/4" or 3/8" thick. | | However, to be fair, I don't know if that kind of strength is required. | | -- | Homo sapiens is a goal, not a description
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I'm not so sure of that Rumpty. Correct me if I'm wrong, but haven't a few tests been done that showed that biscuits don't add any strength? You're absolutely correct in saying that many cabinets have been built using them, but many more have been built without using them, and they're still hanging on the walls too. That really doesn't make the biscuit the reason for the cabinets holding together. I'll agree that the slightly increased surface area provided by the biscuit must increase strength somewhat, but again, remembering back to tests people have published, it does not seem that it was all that great.
--

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There are a few books out on the subject of biscuit joints and most have the strength comparisons.
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Mike,
This always comes up on the wreck that biscuits are good for alignment only. My shop, as well as many other shops have used biscuits for years in all sorts of structural joints etc. They are a wonderful tool. Learn to use them correctly and you won't have any failures.
The Shakers would have loved biscuits.
FWIW, the last thing we use biscuits for is alignment during glue ups.
--
Rumpty

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Your next acquisition should be a good book on the subject. Authors Jim Tolpin, Danny Proulx and Udo Schmidt, amongst others, have done an excellent job in presenting joinery and design methods.
A few things may have changed since you watched your dad.
Note #2: A prototype may be in order, with which you can test alternate methods. You needn't make it full-scale. And the person(s) with whom you share the kitchen then can express an informed opinion before you have to redo it to suit them.
Patriarch, who swears he's a realist, and not a cynic...
ps: Biscuits are great. Pocket screws are great. Together, they're even better.
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Your dad did it right. The rabbet is a stronger joint than biscuits because of more gluing area and fit.

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I'd leave out the brads. nothing like having a nail hit on a biscuit and turn out the face....
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Consider pocket screws (Kreg jig), with or without the rabbet. I like to use rabbets myself. Adds some strength and makes alignment easier at assembly. All in all, easier than biscuits IMHO.
-- ******** Bill Pounds http://www.billpounds.com
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Well folks, thanks for the input, well the varied responses to my question has left me with only one point to ponder, I have had great luck using my biscuits joiner, its worked well for many projects. My first thought was to basicly be lazy and not cut the rabbet, though I knew it was the way to go. Actually my dad build one heck of allot of cupboards in his life and they never fell off the wall. And his rabbet joints never used glue, just finish nails. You all should have seen me taking out the old cupboards ( my dad built them) hammers, recip saw, crow bar, and pull like heck. So i'm going to use rabbets and glue. By the way, most of the carcasses will be 3/4 in birch ply, but I did not want the ends of the cupboards, the ones you see when you come into the kitchen and down the stairs, to be a flat plain, so I have made then out of 1 inch birch stock stile and rail with a flat panel. I think it will look great.
I'll keep ya posted.
Cheers Mike H

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Mike,
For what it is worth, I built my kitchen about 10 years ago using 3/4 birch ply, rabbets, and glue. No failures. I had some ply end panels showing and some with rail and stile panels to cover the ply. Both are fine. I'm just starting the cabinets to go into the new house. Same technique (but with lots more tools this time). Biscuits are nice for alignment, but I still do it the old way-good straight edges glued carefully.
Good luck on your project.
Len ---------------
Mike Harvey wrote:

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