Has anyone actually seen a dado fail to keep case sides straight over time?

[Eric Phelps ON]

Hey All,

I'm wondering if anyone here has actually witnessed a solid case construction (for example lets say dovetailed corners, with a couple shelves dadoed into the sides) have the dado joint fail as the case sides bow / cup over time.

For reference I'm working on a small solid sapele cabinet: approx 16in wide, 25 in tall, 19in deep. Two sides dovetailed into the top, and a shelf offset about 4 in from the floor, dadoed into the sides. M&T faceframes on the front and back.

Originally I thought I might tackle tapered sliding dovetails for the first time, but I don't think on this particular piece its necessary. But I'm still curious if any of yall have actually had problems with solid case sides and dadoes over the long haul.

[Mike Cutler]

If we're talking "real wood", or cabinet grade ply, No, I've never seen it.
For your particular construction, I've always seen the front of the piece pinned close to the front, this allows the width of the shelf to expand and contract at the back. If these shelves are 19" wide, there's going to need to be accomodations built in for them to expand and contract with humidity.

[Eric Phelps ON]

I actually think I’ll be okay in that department. My description may not have been sufficient. The case sides, top, and shelf /bottom are all solid wood glueups, so they should expand/contract at the same rate, and the cabinet depth will fluctuate. The hypothetical “concern” is, if the case side decides it wants to cup along the depth of the cabinet, will the dado joint be able to withstand that without failing.

I’m just wondering if anyone has actually seen a dado torn apart in this way.

[Richard Coers]

I consider the back as most critical status when using dadoes as joinery.

[Eric Phelps ON]

Rich, That’s sounds like a smart way to approach things. This will have a frame/panel back, and face frame front for that matter.

[Mark Rainey]

Eric, a great question. Mike Cutler has never seen it. Neither have I. Is it myth? Is that myth about to be broken?. Everyone, let's see your dados.
Here's mine. These two are from 20 years ago and the mid-size book shelves have seen heavy use and have been moved to different houses several times.

dado 1.jpg Solid butternut - one of my first projects 22 years ago...dado with stub tenon

dado 2.jpgMahogany 21 years ago. Hidden dado.

[Eric Phelps ON]

Mark, Now that’s what I’m talkin about! That’s a pretty solid testament. Can you recall how the backs, if they have backs, are attached? Thanks for sharing.

[Mark Rainey]

Mark, Now that’s what I’m talkin about! That’s a pretty solid testament. Can you recall how the backs, if they have backs, are attached? Thanks for sharing.

Furniture grade plywood in a rabbet secured with screws for the backs.

[Lee Schierer]

I can't speak for sapele, but I made this bookcase back in the 1960's. It is similar to the dimension you listed except for the depth. Mine is only 9-1/2" deep and made from pine. As you can see the shelves are set in dadoes about 3/8" deep. No miter joints on top or bottom just rabbet joints. The shelves were glued in place with Elmers white glue. They are all firmly attached and solid. The finish was Deft Clear wood Finish all those years ago.
20230716_191333.jpg
As you can see the shelves have substantial weight on them. This bookcase has survived at least six state to state moves. The back is 1/8" masonite attached with small nails.

[Mark Hennebury]

I made a small curio cabinet 40 years ago with dado's and cross-wedged tenons, mortise and tenoned frame and panel back.
I don't think the side bowed, just a guess of course.
CabinetDetail.jpgProfil97.jpg027.jpg

[Eric Phelps ON]

I made a small curio cabinet 40 years ago with dado's and cross-wedged tenons, mortise and tenoned frame and panel back.
I don't think the side bowed, just a guess of course.
CabinetDetail.jpgProfil97.jpg027.jpg

Beautiful cabinet Mark. I was actually considering adding a couple of through-tenons to the joint. That would put it sort of in-between the dado and the sliding dt in terms of the technical challenge, and structural integrity as well I would think.

[Eric Phelps ON]

I can't speak for sapele, but I made this bookcase back in the 1960's. It is similar to the dimension you listed except for the depth. Mine is only 9-1/2" deep and made from pine. As you can see the shelves are set in dadoes about 3/8" deep. No miter joints on top or bottom just rabbet joints. The shelves were glued in place with Elmers white glue. They are all firmly attached and solid. The finish was Deft Clear wood Finish all those years ago.
20230716_191333.jpg
As you can see the shelves have substantial weight on them. This bookcase has survived at least six state to state moves. The back is 1/8" masonite attached with small nails.

Thanks for the input Lee. Not bad at all for a cabinet that's been around for ~60years.

Also, I've been pleasantly surprised at how the sapele has been reacting to environmental changes. I milled the boards oversize back in march, and they've sat (stickered) since then in my totally unconditioned apartment workspace. RH in march would have been 35%, and its been around 60-65% since mid june. Out of maybe 20 or so boards only a couple have done funky stuff.

[Derek Cohen]

Hey All,

I'm wondering if anyone here has actually witnessed a solid case construction (for example lets say dovetailed corners, with a couple shelves dadoed into the sides) have the dado joint fail as the case sides bow / cup over time.

For reference I'm working on a small solid sapele cabinet: approx 16in wide, 25 in tall, 19in deep. Two sides dovetailed into the top, and a shelf offset about 4 in from the floor, dadoed into the sides. M&T faceframes on the front and back.

Originally I thought I might tackle tapered sliding dovetails for the first time, but I don't think on this particular piece its necessary. But I'm still curious if any of yall have actually had problems with solid case sides and dadoes over the long haul.

Eric, you would have to experience MASSIVE temperature/humidity swings to cause the panels to bow/cup by greater than the depth of the dados! While there may be some bowing/cupping, it should be minor since the ends are mechanically held by the dovetails.

If you are concerned, there are two methods to follow:

1. Add deeper rebates at the rear, and frame the back.

2. Add on sliding dovetail along the centre of each side. This will anchor the sides.


Just dados in a dovetailed Walnut case ...



... and the vertical dividers since there was no chance of deflection with the full, solid construction design.


These were dados ...



But the vertical drawer dividers were sliding dovetails .... because this was needed to pull the open construction together ...




Unless your horizontal dividers are long and will deflect under load, you should be fine with simple dados.

Regards from Perth

Derek

[Eric Phelps ON]

Derek, Thanks for the tips. I was so focused on wood movement alone, I almost decided I'd never need to attempt a sliding dt. But yes, depending on the construction / application of the piece I can definitely see where I'd want that structural integrity.

That first cabinet must be heavy for its size!

Thanks Again Everyone

[Tom M King]

Sorry I don't have better pictures, but these cubby dadoes are under way more stress, with much simpler construction than any piece of furniture. The cubbies those toolboxes are in are just built from 3/4 and 3/8 construction grade plywood. The verticals are 3/4" with dadoes on both sides for the cubby shelves. Some of the toolboxes are quite heavy. They've been moved multiple times since I built them in 2012. The ones behind the bandsaw and the ones with more boxes stacked on top are not much shorter than 7' tall.

I originally built them for a cargo trailer, but they never ended up in a trailer. They don't have any backs so boxes are accessible from either side. To move, the boxes were unloaded, and the cubbies slid to the door, and lifted onto a trailer. To get them into a house with a raised porch, we slid them over the edge to a pivot point under one of the vertical bulkheads, and pivoted it up onto the porch floor. They do flex noticeably.

They're just stuck together with West Systems epoxy. There are three of them. Not a single joint has broken. I need to build some more because the total number of boxes has grown to over 140 and I only have cubbies for a hundred.

I don't think you have much worry for such construction in a piece of furniture.