To All-
Last weekend, a friend and I assembled an entertainment center we built from 3/4″ plywood. It measures roughly 5’x5’x 18″. Without going into too much detail, the cabinet consists of a top joined to the sides with biscuits, a lower fixed shelf joined to the sides using dadoes, and an offset partition running from the lower shelf to the top, joined with biscuits. There are also two additional fixed shelves toward the top which are joined to the partition and the sides using biscuits. The back is a sheet of 1/4″ plywood 5’x5′ (factory edges). We did a dry assembly on the floor of his garage, and as near as we could tell, everything fit according to plan. Because of the design and joinery methods we had to assemble the cabinet in a particular sequence (top and upper and lower shelves to the partition, followed by sides to the top, shelves, …). After applying glue to the biscuit slots and dadoes, then frantically trying to assemble and clamp, not to mention wrestling with this behemoth to attach the back, we found that we had among other things, gaps where there should not have been (e.g. between the top and partition), the upper shelves were not aligned properly (one was recessed about 1/8″ inside the partition while the other shelf jutted out about 1/8″) ect.
Looking back, I probably should have used poly glue instead of yellow glue because of the setup times involved. For all those who have had similar problems, as well as those experienced in assembling large case pieces, how do you keep these kinds of mistakes from happening? I’m interested in knowing your sequence and approach to assembly and glue-up, and in particular keeping something this large square.
Thanks in advance for all your ideas and suggestions.
T2
Replies
Fitting everything dry is a good start. But for something this big (and clumsy), I'd have done the glue-up in stages.
Stage 1 would have been the top, lower shelf, and the vertical between the top and the shelf.
Stage 2 would have been the two shelves and the side which they attached to.
Stage 3 would have been the bottom and the other side and the back.
To keep the intermediate stages secure, I probably would have used some sort of jig with extra clamps so that the pieces didn't rack while gluing later stages.
John
I won't try to follow all your pieces, but I have a technique that has worked very well for me, assembling large casework.
I have a large L shaped jig - a piece of 2x4 about 5 feet high, with a horizontal leg and a diagonal to make a good right angle. I clamp this to the first side. From this point on, the unit (initially only one piece) will stand by itself.
Then I glue the bottom shelf in place, and clamp it to the first side. Usually this will stand by itself with only one shelf between the sides.
Then I glue and install the next shelf up, and slide the bottom clamps up between the two shelves. The unit is now stable, and basically square (as square as the shop floor is flat, but lets not gripe about uneven concrete)
When I tighten the clamps between the two lowest shelves, the sides bow a little, so the tops are farther apart, allowing the next fixed shelf to be glued and installed. By spacing the clamps, and tightening and loosening, I can work up the case, gluing one shelf (or one shelf and a divider) at a time. Makes assembly easy, even working alone. By the time I get to the top, I slide and tighten the clamps to a good square position. If necessary I put a temporary diagonal in the back to keep the case square, and get rid of the starting jig.
Note that I didn't put the back on at this time. I find large cases far easier to finish if they are lying on their back, on sawhorses. I can even stand inside the case to spray, and don't have to climb or lean over to rub out the finish. The back is finished separately, and installed last.
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Charlie Plesums Austin, Texas
http://www.plesums.com/wood
I've been there. What Johnhardy says is the way I'd go, except add the following:
1. When you dry assemble, make pencil marks for registration at the joints so that you can put the piece back together exactly.
2. When you glue stage one, dry assemble the rest onto stage one and clamp.
3. Repeat for subsequent stages until the final stage is glued.
Tuusche2,
I'm not experienced enough to offer specifics relative to sequence, but I have had enough bad outcomes to offer a few suggestions. The first thing I did when I got my Incra 1000se miter jig was to make a dozen right angle jigs that could be clamped to the sides of the carcas to help keep things square at glue-up time. The second thing I did was to make about 8 cauls so that I could have good pressure across the full dado/carcas side. Whenever possible I try to use my TS and fense in the clamp up...they are flat, square and perpendicular....it helps. Lastly, I will not use biscuits only when joining two pieces of ply...I'll make an 1/8" deep dado and cut the biscuits into the shallow dado....that avoids any gaps from appearing.
With all that the case can still get cockeyed and be twisted.....so I lay in, but not attach, the back panel asap in the process ...
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