Clamping Octagon Joints
Taping the joints and folding them together works the best. November 26, 2006
Question
I am building a custom end table that is an octagon. It is enclosed with raised panels and has two doors at one of the corners. The panels are 10" wide 18" tall. Each panel has a 22.5 degree bevel on each side. I plan on gluing two panels at a time using biscuits, then assembling from there. I have two problems. First, I need a way to clamp the two panels together to start. Second, a way to clamp each set of panels to another set of panels. I don't want to do a band clamp for two reasons: 1) trying to glue several joints at one time and get everything to line up is a bit difficult. 2) I don't have a solid shape because of the doors. I thought about the tape method, but I still don't see how to keep the joint closed.
Forum Responses
(Furniture Making Forum)
From contributor R:
3M makes a strong tape used in v-folding panels, #355. It's very strong and won't stretch. You could butt the joints together and tape them, then roll the joints together. When you are ready to take the tape off, use naptha to dissolve the glue so you don't ruin the finish or raise the grain. I have used this tape for years and you won't believe how nice your joints look.
From the original questioner:
Where can I get this tape, and when you "roll" the joints together, what happens with the biscuits? Don't they interfere? Plus, not so sure about having to dissolve the glue...
From contributor R:
Go to the 3m website, see tape #355. Try to find a dealer where you live so you can buy by the roll. It was about $6.00 a roll last time I bought some. The glue should be stronger than the wood, so I don't use biscuits. I tape all the joints back side first. A couple of pieces across the joint to pull it together, then a piece down the center of the joint vertically, then a piece on each side of that. Rub it down with a solid piece of maple - it will stick real good. After it is dry, when you want to remove the tape, if you don't use naptha, it will tend to raise the grain on your product. Naptha does not affect finishes, but it does a great job dissolving the glue on the tape. That way you don't have glue residue on your product.
From the original questioner:
I may give this a try. Are there any other suggestions out there?
From contributor B:
I have gotten good results by using plain old masking tape to hold eight panels. Spread the adhesive and roll the thing up. Then tape the final joint. That will hold everything in place while you get web/band clamps in place, and using very moderate pressure, snug it down. Then you can peel most of the tape before the glue sets, and clean up squeeze out. I don't know if this will work so easily with biscuits.
From contributor G:
It seems to me that the tape method would be easiest. I've used it with great results. If you're set on using biscuits, though, I think you could get away with using pinch dogs on the top and bottom of each joint (on the end grain of the adjoining rails) to glue it all up. This way, too, you'd be able to glue up all of them at once, or a few at a time - it wouldn't matter. You can purchase pinch dogs at Lee Valley's website, under the clamping stuff.
From contributor T:
I use shrink wrap for these types of glue-ups. The more you wrap, the tighter the joints become. The corners just naturally line up. Try it dry first and see for yourself. Skip the biscuits. This is long grain to long grain. Besides, biscuits are for hobbyists - overkill. If your joints/angles aren't perfect, use PL Premium caulk adhesive. It is thick enough to fill any gaps. I like to over cut the corner angles slightly so that the corners are tight with no glue line and glue is squeezed out the back. PL Premium cures slowly so that you can make adjustments for half an hour or so. I was in Florida last week and noticed it was not available in the Home Depot there.
