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Is clamping box (finger) joints necessary when gluing?

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Forum topic by TopamaxSurvivor posted 08-01-2011 11:15 AM 3743 views 0 times favorited 24 replies Add to Favorites Watch
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TopamaxSurvivor

15088 posts in 2428 days


08-01-2011 11:15 AM

Topic tags/keywords: clamp box finger joint gluing glue up dry fit

I am wondering if clamping a good tight box joint is really necessary when gluing? If they are tight enough to stay in place when dry fitting, do you need to clamp to have enough pressure to make the glue work? Some adhesives are pressure sensitive and you need to hold pressure for a few seconds to make them stick well. Is that the case with wood glue like Titebond II?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence


24 replies so far

View jim C's profile

jim C

1455 posts in 1850 days


#1 posted 08-01-2011 01:12 PM

My guess is with glue in between any joint, it is never quite seated until it is clamped. The glue sitting there is not forced into the porous wood without clamping, causing the joint to be weaker than it would otherwise.
I’m no expert but it’s just my thoughts.
You know the old saying “Squeeze it till it Squirts”

-- When I was a boy, I was told "anyone can be President", now I'm beginning to believe it!

View helluvawreck's profile

helluvawreck

16043 posts in 1618 days


#2 posted 08-01-2011 02:01 PM

Topamax, I think I would clamp it but I’m no expert either. However, another reason for it to be clamped would be that it makes it less likely that someone or something may come along and bump it or knock it off and disturb the alignment or break the bond while it is sitting there unattended.

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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richgreer

4525 posts in 1826 days


#3 posted 08-01-2011 02:30 PM

If I have a tight fitting box joint (or dovetail joint) I don’t bother with clamps. For me, a tight fitting joint is one that requires some persuasion from a mallet to fully seat the joint.

If I have a loose fitting joint, I always clamp.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View Karson's profile

Karson

34916 posts in 3152 days


#4 posted 08-01-2011 04:09 PM

I’ve done a lot of glueing that I slide the pieces to get good glue distributation and then let them sit.

When making toys their are a lot of parts that are impossable to glamp easily if they cdan sit for 20 minutes they are usually hold enough for you to stack them higher. Glue takes about 24 hours to cure fully but Titebond is set pretty well in 1/2 hour or so.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1910 days


#5 posted 08-01-2011 04:21 PM

I use large rubber bands to assure that the finger bottoms seat properly. Before I got the Incra LS setup and used a homemade box joint sled, I would purposely leave the finger joints proud so as to use regular parallel clamps to allow for the clamps to dig in.

IME, you should use some form of light clamping pressure though in order to keep things square, seat those finger bottoms, and firmly seat in your floating bottom panels. Sometimes, I cut box bottoms a little too snug and I need that pressure to close the joints.

-- jay, www.allaboutastro.com

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teejk

1215 posts in 1436 days


#6 posted 08-01-2011 05:20 PM

I vote with Rich. If it’s tight inside and out (and square), I don’t know what the clamps are going to do for you.

View DLCW's profile

DLCW

530 posts in 1406 days


#7 posted 08-01-2011 06:00 PM

You should clamp. Glue will expand and contract as it dries causing your joint to become loose and things not fit right.

-- Don, Diamond Lake Custom Woodworks - http://www.dlwoodworks.com - "If you make something idiot proof, all they do is make a better idiot"

View jim C's profile

jim C

1455 posts in 1850 days


#8 posted 08-01-2011 06:42 PM

I agree with DLCW
Why not clamp it and risk movement? It only takes a second.

Per Titebond II (right on the bottle)

”Surfaces must be clean and dry. Joints should fit tightly.
Apply a heavy spread of glue to surface and CLAMP for 30 minutes. Do not stress joints for 24 hours. Remove excess glue with clean, damp cloth. Close cap after use.

Game, Set, and match.

-- When I was a boy, I was told "anyone can be President", now I'm beginning to believe it!

View Bertha's profile

Bertha

12951 posts in 1445 days


#9 posted 08-01-2011 06:45 PM

I can actually contribute to this! I’ve done them both ways. I found that without clamping, the joint is a lot more visible (if that matters; heck, it might be desirable). I’ve clamped them just to wipe up the squeeze-out and let them sit for as little as 20 minutes to a few days. I can’t say that there’s been any appreciable difference. Once, I let a larger box sit entirely unclamped and it racked itself a bit out of square somehow. I just cranked it back square once dry and kept moving. Fingerjoints are ridiculously strong in my experience. I don’t think they need much help at all.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View SnowyRiver's profile

SnowyRiver

51450 posts in 2232 days


#10 posted 08-01-2011 07:36 PM

I have done it both ways too, but I find the clamps help to seat the joint even if its for 30 minutes or so. I find though its easier to clean up the joint if there arent any clamps on it.

-- Wayne - Plymouth MN

View TopamaxSurvivor's profile

TopamaxSurvivor

15088 posts in 2428 days


#11 posted 08-01-2011 07:45 PM

Thanks guys. I was just curious. I thought they would be fine without clamps after they were seated with a mall, oops, mallet ;-)) or with clamps. Since I used clamps, I left hem on.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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Grandpa

3209 posts in 1427 days


#12 posted 08-01-2011 10:16 PM

I would use clamps and something to keep it square if it is that kind of piece. Somehting like a drawer should be squared. I have some home made squares I use. They are 3/4” plywood triangles. I cut the outer ends parallel to the back so I could use clamps out there. I cut the corner off about an inch in case glue squeezed out. I didn’t want any extra wood glued inside my drawer. I leave them 30 minutes then they can be unclamped and set aside untill tomorrow if you need the clamps. Just my way I suppose.

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Bertha

12951 posts in 1445 days


#13 posted 08-01-2011 10:34 PM

Pa, I bought some expensive Bessey 90-degree clamps. They were so fussy that I use your triangles now;)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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Grandpa

3209 posts in 1427 days


#14 posted 08-01-2011 10:36 PM

I like the Irwin one hand clamps that most folks don’t like. I use them for this purpose and they work well. I can hold the square with one hand and tighten the clamp with the other.

View Bertha's profile

Bertha

12951 posts in 1445 days


#15 posted 08-01-2011 10:57 PM

I have about 20 of those Irwins. Those and some bigger Kobalts are my go-to clamps unless I need the pipe. I don’t own a single K-body but I want them (for no good reason).

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

showing 1 through 15 of 24 replies

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