Domino joints load capacity

[agarwalsa]

I am building my kitchen cabinets and bought a bunch of Festools for the purpose. I am using Domino as the joinery method and hoping someone here could help me.

Will a shelf joined by dominos take the weight of a 30" wall oven (250 lbs) or do I need to reinforce using dados or cleats? As this cabinet will hold the oven, the micro-drawer and a warming drawer, the manufacturer (Wolf) suggests using a 9/16" platform for even reveals for a flush inset installation.  I am planning to use 5/8" plywood for this shelf with 6mm Dominos but a 30" wide shelf holding 250 lbs is making me real nervous.  The sides are 3/4" prefinished plywood.
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Thanks for any advice!

 

[Chris Hughes]

I would cut a mortise to register the load bearing shelf and to shoulder the shelf weight onto the column/side panels.  I would also use dominoes which will help carry the load but mostly keep the shelf on the shoulder.  Usually I cut a 1/8" dado on the MFT, but have found that it is easier cut dominoes first and then the dado.

 

[clintholeman]

What's wrong with using 3/4"?  Domino into place and you're good to go with no worries.

 

[Chris Hughes]

Tearout at the mortise on the shelf.  You are in affect hanging 250 lbs on less then 1/4" of plywood.  The failure would not occur with the domino but at the domino.

 

[clintholeman]

If one Dominos and glues the joint - the load is spread along the perimeter of the joint - all good juju!  And strong. If one wants to add some insurance, put a dovetailed stringer across the middle - Domino'd into the sides.

 

[Chris Hughes]

Not to argue the point, but weight bearing bootoms are a major fail point in case work.  Glue is great but again you've designed a fail point as shifting weight can break a glue joint or tear the two pieces of wood apart while leaving the glue intact.  If it were me, I would design in regards to most likely failure.

Is this not why we use dovetails instead of staples and slot to install a drawer bottom instead of stapling to the bottom of that drawer?

 

[agarwalsa]

Thanks for the replies.

The discussion here is exactly my concern. To answer some questions - There is no space in between the microdrawer below and the platform of the oven to put any stringer down the middle. In fact that is why they suggest using 9/16" platform and not even 3/4" so that the reveal in between the two appliances is consistent with the rest.

Further the glue will not adhere to the prefinished sides so I might have to make the dadoes and reinforce with dominos. If I am using 5/8" plywood for the platform and a 1/8" dado then would you recomment 5mm or 6mm dominos?

 

[clintholeman]

In the drawing they show separate pieces - stacked, which is essentially a dado all the way through.  If this is a drawing from the mfg., I would build it like that in order to keep the warranty with no questions.

If this is your drawing, then one would need to know where the load bearing pieces are and how heavy they are at the contact points and their footprint and work out a static load for the piece, then see how that fit with the wood specs.

I don't think I would vary from the spec drawings.

 

[Dane]

You definitely need to dado that.  You need a continuous load path from the edges of the shelf to the floor or whatever support structure you have running along the bottom of the cabinet.  The dominoes are plenty strong enough, but as was said before, that 1/4 inch of ply that will be the bearing structure will be a fail point.  I take the point about the glue bond being strong, but unlike in solid wood, you also need to think about the glue bond holding the veneer to the substrate of the plywood.  You are essentially relying on the veneer layer to take the load.  I can just picture the ply failing at the domino joint and the added weight causing the veneer to peel away from the substrate, I have seen it happen. 

But hey, now you can use the OF1400 and guide rail!  An excuse to buy more tools!

 

[mastercabman]

I have done a lot of those platform for ovens.If you don't have any room for cleats,I would dado with the dominos.
But i wouldn't rely on just dominos for that much weight.

 

[agarwalsa]

This is the manufacturers drawing and yes it is showing separate pieces - essentially a dado as you pointed out - I did not notice that. Thanks for pointing out clintholeman! I will see if I have space for that else I will go with dado+dominos.

Thanks for all the help !

 

[Brice Burrell]

This is the manufacturers drawing and yes it is showing separate pieces - essentially a dado as you pointed out - I did not notice that. Thanks for pointing out clintholeman! I will see if I have space for that else I will go with dado+dominos.

Thanks for all the help !

I was having trouble figuring out your problem with the construction. But I guess you didn't look closely at the drawing and that's why you were thinking about dados. I'd built it exactly as shown in the drawing, screwing the joints, no dados or Dominoes. I'd screw the warmer box together wholesale then make up the microwave and oven portions three sided and join all three with pocket screws.

 

[clintholeman]

Instead of pocket screws, one could Domino the pieces to hold them together.  That is what I would do, even with a stack construction, just to hold the walls vertical.  Pocket screws would work, of course, but I don't use them.

Again, I think it is important to follow the drawings as closely as possible.

 

[agarwalsa]

Just when it all starts making sense, I looked at the entire drawing and it looks they have supported it just on cleats.

Will a 1" narrow (3-4") hardwood cleat be stronger than a 3/4" plywood sheet used more as a wall rather than a  cleat?

and yes Dominos could be substituted for pocket screws.

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[mastercabman]

This is the manufacturers drawing and yes it is showing separate pieces - essentially a dado as you pointed out - I did not notice that. Thanks for pointing out clintholeman! I will see if I have space for that else I will go with dado+dominos.

Thanks for all the help !

I was having trouble figuring out your problem with the construction. But I guess you didn't look closely at the drawing and that's why you were thinking about dados. I'd built it exactly as shown in the drawing, screwing the joints, no dados or Dominoes. I'd screw the warmer box together wholesale then make up the microwave and oven portions three sided and join all three with pocket screws.

OK,So this cabinet is designed to be 3 pcs,then stack on top of each other?  In that case then do what Brice is suggesting.
Are the sides going to be exposed?  If so,Are you going to put some kind of skin/panel on the sides to hide the seams?

 

[agarwalsa]

Thanks mastercabman and Brice.

This has been very helpful and I think I have this clear now. I will use what Brice suggested and keep the width 30 3/8 (the sides and construction will then be hidden by the face frame) and then put in the cleats if needed to make the cabinet space meet the spec as shown in the drawing.

The sides are not exposed so that is not my concern.