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View Belg1960's profile

plywood carcass construction dado depth

by Belg1960
posted 542 days ago


21 replies so far

View bluekingfisher's profile

bluekingfisher

987 posts in 1565 days


#1 posted 542 days ago

Pat, usually about half the thickness of the material, therefore 3/8” although 1/4” is suitable for some projects.

I wouldn’t however exceed half the thickness

-- No one plans to fail, they just, just fail to plan

View bondogaposis's profile

bondogaposis

2416 posts in 937 days


#2 posted 542 days ago

I go 1/4”.

-- Bondo Gaposis

View ClayandNancy's profile

ClayandNancy

479 posts in 1601 days


#3 posted 542 days ago

What if you have two dadoes on opposite sides at the same spot? Is 1/4” ok or too much?

View SamuraiSaw's profile

SamuraiSaw

429 posts in 550 days


#4 posted 542 days ago

Agreed on not exceeding half the thickness. A lot depends on the span of the shelf, if there is a back to the cabinet, and the fastening mechanism of the shelf. If you will be using screws to hold the shelf in place or if you will be able to attach the back to the shelf a 1/4 dado will be sufficient. All you’re doing is registering the shelf to the side. If the sides are visible you’ll want to go deeper to provide more stability.

-- Artisan Woodworks of Texas.... www.awwtx.com

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1744 days


#5 posted 542 days ago

I normally do 3/8”, but beware that 3/4” plywood is not necessarily 3/4” .

-- jay, www.allaboutastro.com

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1744 days


#6 posted 542 days ago

@ClayandNancy – I would use a 3/16” dado in that situation, likely also mounting it in a face frame or edge banding.

-- jay, www.allaboutastro.com

View JesseTutt's profile

JesseTutt

792 posts in 696 days


#7 posted 542 days ago

I tend to use about 1/4 to 1/3 the thickness of the material, so I would normally use 1/4 dado on 3/4 plywood. I would use less if I had a dado at the same location on the opposite side.

-- Jesse, Saint Louis, Missouri

View Gene Howe's profile

Gene Howe

5267 posts in 2014 days


#8 posted 542 days ago

As SamuraiSaw said, it depends on the application. However, with today’s glues, 1/4” is sufficient for MOST applications. It’s the span and prospective weight on the shelf that deserve consideration. The actual joint will be strong and solid.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1744 days


#9 posted 542 days ago

@Gene – I’m trying to think when you’d even need glue (from a structural standpoint), especially if there’s a face frame and cabinet back to lock it in? To me, I often just glue it in to make sure it doesn’t shift around and rattle over time.

-- jay, www.allaboutastro.com

View SamuraiSaw's profile

SamuraiSaw

429 posts in 550 days


#10 posted 542 days ago

I always glue shelves/partitions in place to provide additional stability. I’ve never had a customer complain because I over-engineered a piece, but I have certainly regretted the opposite when (and invariably it will) a joint fails and I have to repair it.

-- Artisan Woodworks of Texas.... www.awwtx.com

View Belg1960's profile

Belg1960

779 posts in 1651 days


#11 posted 542 days ago

The span on the two units is only 20” and it will have a back of either 1/4 or 1/2 material probably luan ply.
Another thought I’m using unfinished ply to build these but decent quality material, to hand finish it would most of you assemble first, or prefinish large sections and then machine them? And assemble after?
For the smaller cabinet like this I think the 1/4” will do, for the dado. Never thought about the situation where 2 dados would be at the same height but not in this case. Thanks much

-- ***Pat*** Rookie woodworker looking for an education!!!

View SamuraiSaw's profile

SamuraiSaw

429 posts in 550 days


#12 posted 542 days ago

If it is stain grade, I tend to machine the parts, apply stain, then assemble and top coat. That helps prevent problems with glue interfering with the stain. If paint grade, do the complete assembly then finish.

-- Artisan Woodworks of Texas.... www.awwtx.com

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1744 days


#13 posted 542 days ago

@Samurai – I’m not suggesting that you could always leave this joint unglued. I wouldn’t. I was thinking more in terms of a shelf/divider (see OP) as opposed to the cabinet box itself. I should have clarified that.

-- jay, www.allaboutastro.com

View SamuraiSaw's profile

SamuraiSaw

429 posts in 550 days


#14 posted 542 days ago

Cosmic, I tend to over-engineer stuff. My theory is if you can’t park a car on it, beef it up!!!

-- Artisan Woodworks of Texas.... www.awwtx.com

View bondogaposis's profile

bondogaposis

2416 posts in 937 days


#15 posted 542 days ago

What if you have two dadoes on opposite sides at the same spot? Is 1/4” ok or too much?

In that case I’d go 1/8”.

-- Bondo Gaposis

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1744 days


#16 posted 542 days ago

I hear you, SS.

-- jay, www.allaboutastro.com

View Lee Barker's profile

Lee Barker

2163 posts in 1436 days


#17 posted 542 days ago

Industry standard is 1/3 the thickness of the vertical material. That holds true for dadoes both sides. There’s no structural concern here because the load is down, not lateral.

The compelling reason to keep them the same is that the math stays constant; therefore, the machine settings and the shelf adds do not vary. This can be critical to consistency and quality.

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View ClayandNancy's profile

ClayandNancy

479 posts in 1601 days


#18 posted 542 days ago

Samurai and Bondo Thanks there will be a face frame and a 1/4” or 1/2” back. Sorry Belg1960 for hijacking your post. As for normal dadoes in ply I go 1/2 the thickness, glued and sometimes I use brads just to help hold until the glue dries.

View Belg1960's profile

Belg1960

779 posts in 1651 days


#19 posted 541 days ago

Thanks for the input guys, all the info was taken in for future projects.

-- ***Pat*** Rookie woodworker looking for an education!!!

View BinghamtonEd's profile

BinghamtonEd

1149 posts in 955 days


#20 posted 541 days ago

I’m in the process of building a kitchen island for my wife, and just glued/screwed the cabinet box together yesterday. The box has the bottom and one shelf. Sides and horizontal pieces were made out of 3/4” ply, with dadoes 3/8” deep. Back was 1/2”, with 1/4” dadoes for the horizontal pieces. Strips of 3/4” pocket-screwed across the top to fasten the top to. Bottom shelf also is screwed in from outside of cabinet through the dadoes (to be covered in trim later). Overdone? Maybe. But when it came time to assemble the whole thing, it all came together rock solid and square. I should also note that this is a mobile island with a butcher-block top, so it will be going through slightly more stress than some other basic cabinets might.

On a side note, like others have said, measure your plywood first. I bought plywood listed as 23/32, used a 23/32 dado bit and come to find out, nothing fit, because the plywood was actually 3/4”. Rather than re-route all of my dadoes on the sides and back, I just used the dado bit to cut a 1/32” rabbet on the undersides of the bottom and shelf to bring the mating thickness down to 23/32.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View oldnovice's profile

oldnovice

3520 posts in 1953 days


#21 posted 541 days ago

I agree with Lee. Simplicity and consistency!

-- "I never met a board I didn't like!"

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