Blind Dado vs. Butt Joint

[Brett Nelson]

Forgive the heresey for a moment. Planning to build a house full of cabinets out of 3/4" melamine. :o They will all be painted except for one piece, that will be dark dye stained alder.

Anyway, gonna send my ecabinet files to a shop to have the parts cut and wondering if I should specify blind dadoes or butt joints with confirmat screws. ???

[Chris Padilla]

I would just do the confirmat screws...they work very well in this situation. I would imagine it would be cheaper than the dadoes you are thinking about.

[Mike Cutler]

I'll offer a contrary opinion to Chris' and say to go with the blind dado's.
I'm sure that the confimat screws have a lot of "engineering fat" in their design and application, but the shoulder that the dado offers can't be ignored for strength.

[Brett Nelson]

I'll offer a contrary opinion to Chris' and say to go with the blind dado's.
I'm sure that the confimat screws have a lot of "engineering fat" in their design and application, but the shoulder that the dado offers can't be ignored for strength.

There really isn't much of a cost increase by going with the dadoes. The shop charges me per sheet to cut the parts regardless of joinery. So the only cost increase is that dadoes require a bit more material.

I usually work with ply rather than melamine. I know that the melamine coating doesn't accept glue at all, thereby necessitating the confirmat screws. But, how well does the PB core accept glue. IOW, does the blind dado create enough core:core glued surface that I would no longer need the screws?

[Chris Padilla]

Use Roo glue...not the most pleasant stuff to work with.

[frank shic]

pin them while the glue dries so you don't have all those clumsy clamps in the way

[jack duren]

Adding the blind dadoes will help with alignment of the parts. You only need change the configuration in eCabinets. If your building kitchen cabinets,you should or should get a 1/4 staple gun. Most melamine cabinets are covered by veneer or laminate and cover the staples. Roo glue or similar works on melamine.

Are yo building single units or ????....Jack

[Peter Quinn]

How about blind dados with confirmat screws and a bit of glue? I've seen cabs cut by Halls Edge, who supports the ecabinet's software, absolutely perfect. The samples I saw were blind dados in 3/4" plywood, frameless setup that came edge banded. The joinery was so tight a 220# man could and did sit on the dry assembled boxes without fasteners! It would take me forever to do what a thermwood CNC can do in minutes. Strong stuff.

IMO butt joints are the stuff of the lowest grade of production cabinets, and if a CNC machine is doing the milling, why not get the premium strength? You will get ten guys to tell you they have been using but joints for years and no call backs, I say bologna! I've seen that junk fail too many times a few years down the road. Not in my house, and certainly not for uppers.

I like dados with screws for rabbits in carcasses in any event, perhaps a simple Hi/lo particle board screw would suffice? Or maybe SPAX? The problem with glue alone on particle board is that while it will bond the leading edge effectively, the material beneath is week so the joint provides little strength. That is why good screws are necessary beyond just clamping force and glue. The glue is a bit of added security, the screws are the business end of the operation.

Roo glue I believe is meant to glue the cut butt end of a horizontal member to the melamine face of a verticle member. With butt joints you may want them to drill for dowel reenforcement and should use confirmat screws. Perhaps you could get the confirmat screw holes drilled by the fabricator as well regardless of which method you choose?

[Mark Boyette]

Personally I'd go with dados. Makes for a very easy assembly also. They do make a melemine glue but I'm not completely sold on it's strength.
I do a ton of melemine cabinets this way.
Dado the bottoms, rabbet the 3/4" back in, drawer dados only have to go back 7" or so.
Titebond wood glue and 1 1/4" staples and you're set. If I have a cabinet that is over 24" I do screw the back to the bottom. Not a big deal since this is on the backside of the cabinet. Laminate wood on finish sides, wood edgeband and you have a nice cabinet for stain or paint.
If you really want to add screws just put a 1 5/8" drywall screw into the dado but it's really not necessary. 1 1/4" don't seem to sink into the melemine face but 1 5/8" work very well and countersink themselves flush.
PM if you want additional info.
hope this helps.
Mark.

[Mike Cutler]

IOW, does the blind dado create enough core:core glued surface that I would no longer need the screws?

I wouldn't use glue only in this application. I think you need the engagement of the fasteners, no matter what the adhesive used. I tend to go for overkill though.
I always remember the words of my woodshop teacher when screws are used. " Think of a woodscrew as a permanent, disposable clamp."
.

[Joe Chritz]

It is difficult to argue that lots and lots of cabs are built with just butt joints and confirmats. The question is how far over built do you want them?

I am surprised there isn't a substantial increase in cost for dados since there is a lot more machining involved. If the cost is close then by all means go with the dadoes. They will increase strength and make alignment many times easier and faster. The alignment issue alone is probably enough to justify a decent premium in cutting cost.

Yes use some kind of fastener. Staples then a few screws would suffice.

Joe

[jack duren]

"You will get ten guys to tell you they have been using but joints for years and no call backs, I say bologna! I've seen that junk fail too many times a few years down the road."

Works just fine. A lot of shops dont have access to CNC and dont dado of any kind. Butt joints, staples and screws are used all the time. We send a lot of upper units out up to 48" long. Architects design these cabinets. We create the shop drawings. They are resent for approval and are signed off. Cant always blame the cabinet shop;)....Jack

[Sonny Edmonds]

While I don't know much about particle board coated with anything, I do know a bit about dovetails.
I wouldn't have a non-dovetailed drawer. The dovetailing speaks of craftsmanship and care in the strength and longevity.
It takes care, planing, and concentration.

Butt joints are the weakest of all joints. I'm surprised that if you want fast, cheap, and easy, you aren't considering drawer lock (http://www.woodmagazine.com/woodworking-plans/routing/drawer-lock-bit/) joinery.

Anyhow, I like dovetails. Mama's Lingerie Dresser is solid oak and the only metal used is the drawer pulls. Otherwise it's solid oak, precision joinery, and glue. The drawers are dovetailed on all corners.

[Mark Boyette]

very nice sonny!
Mark.

[Dennis Hook]

My first post so an intro is in order I guess: I have been in commercial cabinetry for the past 26 years. I love building, making stuff and would do this as a hobby, which it is as well, if it weren’t my occupation. Guess you could say I get paid to play.

One thing to consider is the gain versus loss of the dado. The glue surface provides little tensile strength, as Peter noted, and you are better served by using a proper staple and screw format.

The dado does provide a good amount of shear strength but what is often not considered is the loss of structural integrity of the vertical panel when the melamine surface is compromised across the entire surface. Rabbits are fine but the weakness of the panel with a dado is not worth it in my opinion.
I would suggest using biscuits if shear strength is a concern.

Dennis

[Sonny Edmonds]

Thanks, Mark.
It is destined to be an heirloom.

[Sonny Edmonds]

Hi Dennis!
Welcome to the creek from a new comer as well.
I'm a home hobbyist woodworker.
But I love wood and what I can find in it. :)

[Dennis Hook]

Hey Sonny,
Thanks for the welcome. Buy the looks of your work, you do your hobby proud.

[Brett Nelson]

Thanks for the responses guys. I'm thinking I will go with the blind dadoes, Roo Glue, and staples. I already have a 1/4" crown stapler. Does everyone still think I should throw a few screws in there too?

As far as cost is concerned... The guy running the shop normally just charges $30/sheet without any upcharges for the different types of joinery. I'm probably gonna go ahead and have him fabricate my drawer box parts too as he won't charge me extra for dovetails. Probably go with Baltic Birch there.. prefinished. I'll be using Blum Tandem with blumotion, so the dovetails will look really nice when the drawer opens. I had considered going with ply for the carcases too, but there are a ton of cabinets and I don't think I can afford the cost increase on this one. Gonna spend some extra money on large cornices throughout most of the main floor. I'll try to post some pictures as I get things going. BTW, does anyone have any ideas on traditional mantels and box newels?

[Brett Nelson]

I forgot to also ask. If you would still add some screws with the staples and glue, would you go all out and use confirmat screws, or just something more light weight?