Assembly clamping pressure

[Matt Benton]

I am about to assemble a dovetailed blanket chest. The sides have about a 1/16th gap over 16" where they join the front of the chest. Is this too much to force square during assembly? I'm afraid that if I do, the joint could come apart down the road...

Thanks!

[Chris Friesen]

Do the dovetails lock it mechanically, or is it in the other direction?

If you can straighten it out by hand it's probably okay. If you need clamps to straighten it, you might want to rethink things.

[Matt Benton]

I didn't quite make the joints tight enough, so no, the boards don't straighten mechanically, although I can straighten them with physical force.

I'm starting to think my best bet is using an Epoxy with light clamp pressure, since I have a few gaps to fill anyway. Just really don't want this coming apart down the road....

[Bob Coleman]

Matt -

The glue will be stronger than the wood (at least titebond is) so you shouldn't have a problem using clamps to straighten everything out upon glue-up. I had basically the same problem with a mahogany blanket chest I made last year (I'm at work so I can't post pictures, but look in "projects" for some). I was working sporadically so there was a month or two between milling, cutting dovetails, and glue-up.

You bigger problem might be if you marked and cut the dovetails with the board clamped straight or not. That might affect how it goes together.

Long story short - I would clamp them straight.
-Bob

[Matt Benton]

Bob/Chris,

Thanks for the replies. The boards go together without any problems. They are fairly tight, but not overly so.

Think I'll try Titebond III, as it should match the walnut better. I'll clamp them down and let you all know how it goes...

[glenn bradley]

A little persuasion is probably OK. The side effect to watch out for is that by forcing the joint closed the tension is such that you pull the carcass out of square once the clamps are released. This can be very disappointing; DAMHIKT.

[John Coloccia]

Do the dovetails lock it mechanically, or is it in the other direction?

If you can straighten it out by hand it's probably okay. If you need clamps to straighten it, you might want to rethink things.

I usually use a couple of fingers to check. If it feels like I could close it up with just a couple of fingers, I close it up. If not, I'll figure out what went wrong, and try to correct it if I feel I have to. I've found that Titebond does indeed creep, I don't care what the literature says. If I'm depending on the glue joint to keep things square, I'll fix it. If the joinery is keeping everything square, and all the titebond has to do is keep it from falling apart, I'd probably just clamp it if it wasn't too bad. Does that make sense?

So for example, I stole a great idea from Robert Benedetto and I make my guitar neck dovetails so it's tighter on the bottom than up near the neck. That sucker will never pull away at the heal under string tension so I don't worry about Tightbond creep. If I were using a more traditional joint, I would use a different glue (probably hide glue) that doesn't creep.

[Matt Benton]

Keeping the carcass square will not be an issue. It isn't enough deviation to throw the whole chest out of alignment.

All the glue needs to do is close up the gaps 3/64th or so where the tails meet the pinboard. I can close the gap with hand pressure, so I think I'll use either Titebond III or something else that will match walnut.

Will the hide glue fill any of the smaller gaps I have, or should I look to epoxy?

[John Coloccia]

Hide glue doesn't fill gaps very well at all. For hide glue to work properly, you really need a more or less perfect joint.