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Dado joints -- how tight is too tight?

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Forum topic by nwbusa posted 366 days ago 1528 views 0 times favorited 15 replies Add to Favorites Watch
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nwbusa

1015 posts in 788 days


366 days ago

Or, I guess a better way to put it is, how much “slop” do you allow for when cutting your dado joints? I’m building my router table cabinet (version two) now, and I have my dado stack set to allow a tight fit with just moderate hand pressure, but that’s on a 3” wide piece of scrap. I’m wondering if that might be too tight over a 20” joint, especially when glue is added. Would an extra .002” or .005” be a smart move, or would that be too sloppy?

I know this kind of stuff comes with experience and we all have our own ideas about what constitutes an acceptable joint, but I’d appreciate opinions on this one.

-- John, BC, Canada


15 replies so far

View darthford's profile

darthford

518 posts in 426 days


#1 posted 366 days ago

Add some clearance, how much depends on the wood, glue, environment. Recommend you mill some scrap for trial purposes. I once marveled how perfectly I milled some dovetales, until I applied glue and the fibers swelled up and I had to beat it together with a hammer.

View steve's profile

steve

316 posts in 495 days


#2 posted 366 days ago

I simply cut a dado to fit as tight as a firm press-in by hand or soft mallet blows allow. I always put glue “in” the dado, spread it with a small brush, and clamp, or pin with a pin-nailer, or brad nailer. Done.
There is really no need, I have found, in complicating a perfect joinery system as dado joints. Just make sure the cutter blades, are cutting square cuts at a snug fit. I generally use a router for my dados, I have plywood sized bits for undersized ply. And straight bits for sized material. With the stacked dado, just test cut with shimming and have a snug/tight fit. Use glue sparingly. It does not require a lot of glue to secure a joint. The mistake, in my opinion, most people make is over applying glue…and OVER-thinking stuff. Good luck.

-- steve/MA/USA

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steve

316 posts in 495 days


#3 posted 366 days ago

Woodworking is not AS complicated and glossary/definition filled as many…umm, LB’s would make you “feel” sometimes. I’ve let “woodworker” intimidation of values influence me in the past, but have thought better about my approach to further projects, and have found that my most instant, first instinct, has become the correct way to attempt my issue in the first place. Ask, ask questions…above all, never stop seeking knowledge, but be simple in your attack of the original issue…it usually ends up being a logical reason why something “seemed” problamatic. Peace.

-- steve/MA/USA

View Grandpa's profile

Grandpa

2984 posts in 1177 days


#4 posted 366 days ago

I like my joints to fit snug but not tight. I want to be a ble to spread glue and assemble without a hammer. This has worked well for me for over 50 years so that is my story. The joints are still holding and I was able to get them together. I think there is some experience required because snug to me might mean tight to you and loose to Bill. This is about like knowing how fast to travel with a router.

View Moron's profile

Moron

4666 posts in 2395 days


#5 posted 366 days ago

snug but not so tight as I need a mallet to fit them together. Glue has a tendency to swell wood, to the point where snug becomes tight, and tight becomes impossible

-- "Good artists borrow, great artists steal”…..Picasso

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MonteCristo

2088 posts in 690 days


#6 posted 366 days ago

Snug, but it’s also worth remembering that dado joints don’t involve long grain to long grain contact anywhere, so they are inherently weak as a glued joint. They are also not mechanically strong in all directions . . .

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View nwbusa's profile

nwbusa

1015 posts in 788 days


#7 posted 366 days ago

Thanks guys. I’m using Baltic birch plywood for this project, and I probably cut the dados a little on the snug side this time, but if need be I’ll sand the board edges a bit.

-- John, BC, Canada

View MT_Stringer's profile

MT_Stringer

1553 posts in 1733 days


#8 posted 366 days ago

I took a different approach. I made a jig similar to the one in The Wood Whisperer's video of his exact-width dado jig with a few changes.

Mark uses a guide bushing and a straight bit. I used leftover stuff I had in the shop which included some 1/2 inch mdf. Like his jig, I made one side fixed and the other adjustable. The difference is I used a flush trim bit and simply followed the mdf sides until I had cleaned up the pass. I make three passes to get a 3/8 inch depth.

I just finished gluing up a book case and the dados fit great. I am using white pine that has been ripped, glued up and planed to smooth. So obviously, the boards are shy of 3/4 inch but with this jig, it doesn’t matter as long as it is greater than 1/2 inch for the trim bit to make the cut.

Hope this helps.
Mike

Watching glue dry…BORING! !!

-- Handcrafted by Mike Henderson - Channelview, Texas

View Moron's profile

Moron

4666 posts in 2395 days


#9 posted 366 days ago

a few well thought out and well placed, hidden pocket holes for screws (with a “Kreg Jig”) can turn a weak joint into a much stronger one, and if you step the dado joint and make it a dado rabbit ?……you can pull the joint tight, in any direction for long enough to effectively make a superior piece of cabinetry within the parameters of how long glue remains effective.

Simplified

never panic and stay calm : )

-- "Good artists borrow, great artists steal”…..Picasso

View nwbusa's profile

nwbusa

1015 posts in 788 days


#10 posted 366 days ago

Calm is my middle name!

-- John, BC, Canada

View pintodeluxe's profile

pintodeluxe

3032 posts in 1315 days


#11 posted 366 days ago

I like dados for case construction. Just a friction fit will do. Super accurate with a dado blade on the tablesaw. I usually add some additional reinforcement to a case assembled with dados, such as a through tenon or pocket screws.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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Moron

4666 posts in 2395 days


#12 posted 366 days ago

how to fix fkd

is easy if your not paying for it

: )

I figure that wood is one of the greatest teachers on this planet

it always gives you the test before the lesson

-- "Good artists borrow, great artists steal”…..Picasso

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Moron

4666 posts in 2395 days


#13 posted 366 days ago

mastering a single joint is hard enough

trust me ?

take some time to wonder and quit worrying about failing as that is an inevitable fact too many seem to forget. Those who have self imposed rules can say what they may and claim what they claim but seriously it is possible to think rapidly and doing a “dado joint gone bad”

isnt the end of the world from this dudes perspective

-- "Good artists borrow, great artists steal”…..Picasso

View nwbusa's profile

nwbusa

1015 posts in 788 days


#14 posted 366 days ago

Everything is a matter of perspective, truly.

-- John, BC, Canada

View Moron's profile

Moron

4666 posts in 2395 days


#15 posted 366 days ago

suddenly the “fun” is removed and the “intellect” has to kick in

from hunting to being hunted, the indistinguishable line between knowing the difference is thin at best

-- "Good artists borrow, great artists steal”…..Picasso

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