How many clamps?

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I find that the more simpleminded the question, the more likely people here will argue about it. This should be interesting.
I'm finally getting ready to attach the face frames to my first two bookcase units. Apart from some pocket screws for the top and bottom rails (whose holes will never be seen), I plan to just glue and clamp. I took a first stab at laying out where the clamps should go. I find that it's a little less nerve wracking if I have all of the clamps at hand and set to something like the right opening before I apply any glue.
http://www.flickr.com/photos/gdguarino/8583909737/in/photostream/lightbox/
and
http://www.flickr.com/photos/gdguarino/8585009670/in/photostream/lightbox/
I have two questions:
Do I need three clamps for each rail, as shown in the photos? Or would two (plus the clamps at the ends of the rails) be enough? The units are 21" wide.
I have shown five pipe-style clamps on each side (one at each T intersection) plus some cheap bar clamps in between the shelves that are further apart. Do I also need clamps between the shelves that are closer together? Those are 11.25" apart on center.
I feel I'm going to get a lesson on cauls, which, if quick and simple, I could consider. But my spare time has become very spare indeed lately.
Thanks in advance.
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Looks like enought to me if you use some cauls or blocks with those bar clamps.
--
Often wrong, never in doubt.

Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar. org
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You only need enough to eliminate/close the gap.

See above.

Calls would eliminate the need for so many clamps b

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On 3/24/2013 12:32 AM, Leon wrote:

Thanks for the helpful advice. I inspected the contact between the face frame and the unit with the clamps on (dry) as shown in the photos I posted. I could see a gap in one spot and made a mental note to add a clamp there as per your suggestion.
When I removed the clamps and the face frame to prepare for the actual gluing, I noticed that there was a very slight "lump" of glue near where I had seen the gap; it must have squeezed out of the end of the dado when I glued in the shelves. A few passes with a block plane evened it out nicely, there, and in another location. After I applied the glue, face frame and clamps, I inspected that area again: No gap.
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On Sat, 23 Mar 2013 21:19:32 -0700 (PDT), Greg Guarino

Despite the holding properties of proper glue usage and clamping, I'd never just glue on any part of your project. Almost everything I build, I overbuild. To that end, I'd use my Domino and/or my Kreg wherever possible.
But, if I was just gluing, I'd clamp the face frame enough to close any gaps.
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That's one of the reasons that I made all of the shelves fixed, in dadoes. My experience is limited, but I have trouble imagining these boxes failing with so many glued joints. They will also have backs, rabbeted in, and the face frames.
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On 3/23/13 11:51 PM, Dave wrote:

Coming from someone (me) who generally over-engineers everything, your statement in way too general to be good advice. :-)
You said it yourself in your first sentence, "Despite the holding properties of proper glue usage and clamping..." If there's no load on a joint, it's just plain silly to use dowel/tenons or screws for strength. In any non-load bearing joint, if the glue alone isn't strong enough, the joint isn't designed properly. Even a butt joint with modern glue is strong enough.
Unless they are serving another purpose, screws or dowels/tenons are a waste of time and resources. Tenons for alignment are a another story. They are great way to help perfectly align a joint while clamping or until the glue cures.
Pocket screws are a great way to clamp, but according to Kreg and confirmed by my experience, they negate the need for glue. I use pocket screws to clamp all the time, in places they won't be seen, when I don't have enough clamps or I don't want to wait for the glue to cure before moving to the next step in the project. Sometimes, after the glue dries, I'll take the screws out and recycle them because the are no longer doing anything useful-- they were simply tiny clamps.
For the OP's bookcase project, assuming he used dado joints for the shelves, I see nothing that requires anything other than glue for strength and holding.
--

-MIKE-

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Dave wrote:

"-MIKE-" wrote:

------------------------------------------------------------ With the advent of modern day adhesives, the relative strength advantage of fastners v. adhesives for joints is greatly over rated.
Ever wonder how Boeing is securing all that carbon fiber they are using to build the current airplanes they are producing?
Think maybe various epoxy formulations might be involved?
Adhesive for shear load applications is a tough joint to beat.
Tensile load joints, not so much, but then tensile joints are no winner for fastners either.
Lew
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The cabinet sides and shelving are plywood. That being the case, he would be gluing hardwood face frames to plywood edging. Maybe I've been doing something wrong all these years, but I've *never* been able glue wood to plywood edging and been able to call it a strong connection.
That's my reasoning for more than just glue.
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On Mon, 25 Mar 2013 06:51:25 -0400, "Mike Marlow"

Oh, I'm not saying that the face frame will move, just that my building preferences demand that most of what I build are comparable to a tank.
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If you have kidds and especially if some of them are boys that is the wise thing to do!
--
Better to be stuck up in a tree than tied to one.

Larry W. - Baltimore Maryland - lwasserm(a)sdf. lonestar.org
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On 3/25/2013 2:31 AM, Dave wrote:

I'm curious, did any such joints actually come loose? Did you perhaps try to pry one apart and find that it was indeed weaker than you would like?
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On 3/25/2013 11:32 AM, Greg Guarino wrote:

Greg, you won't have a problem with the face frame coming off. it will be fine.
--
Jeff

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On 3/25/2013 11:43 AM, woodchucker wrote:

At this point it really was more curiosity than worry. I'm always up for learning something more. In any case, the gluing was done yesterday evening. :)
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Greg Guarino wrote:

I don't know about him but I have *NEVER* had a glued joint fail. One of mine, that is.
A while back I had to make a couple of glued up arched jambs. I drew my arc on a piece of ply, put short pieces of 2x4 on edge at a few tangents. I attached them by squirting some yellow glue on them and pressing in place (no clamps). When I finished with the jig I reclaimed the plywood by knocking off the 2x4 pieces with a hammer. Generally took more than one hard blow and each one took plywood with it. NP, other side is still good.
--

dadiOH
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I've glued hardwood to hardwood, pine to pine and a combination of both and they've stood up well. It's just the gluing of solid wood to plywood edging that I've had this problem. Never could figure out why.
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Initially, I glued a 1" thick strip of pine to a plywood veneered table edge that I built. It started coming off about a month after I built the table.
I removed all the pine edging and then shaved about 1/4" off the plywood table edge to remove the remnants of soaked in hardened glue. Then I tried gluing again with a different brand of yellow carpenter's glue. Same problem happened again about two months later.
All of this seems really strange because after the second try, I glued on a roll of veneer stripping and that's stayed on quite well ever since then.
I can only surmise, that pressure (such as elbows) put downwards force on the table edge. Other than that, to be honest, I'm not sure where the problem lay. Maybe it was me and my technique, the type of glue I used or something else.
That's my limited experience with it. I've never tried again.
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On 3/26/13 3:40 AM, Dave wrote:

I wish you had pictures so we could help you out better. My first instinct is not tight enough clamping. Long shot, though, since it doesn't take much pressure at all. As another poster stated, just enough to close the gap.
My second is wet wood-- the pine, maybe. Silly question, but was either product pressure treated in any way? Was the pine recycled from another project and treated with any kind of finish or solvent?
(Please don't think I'm trying argue, here.)
--

-MIKE-

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Nothing pressure treated or finished in any way ~ at least before the glue dried and then I applied a Minwax stain and finish.
It occurred to me that the glue I applied didn't adhere well to the layers of wood already glued together with the plywood. Or maybe, just really poor quality plywood. In any event, it was a number of years ago that I last worked on this and I haven't tried a similar construction since.
Maybe it's time to try again, if only for information's sake.
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On 3/26/13 4:26 PM, Dave wrote:

I would encourage you to try it again if the need arises. It really is an easy and effective way to make plywood stronger and look a lot better.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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