Festool Domino Help with an angled joint

[DeejayK]

Hi All,
Feeling slightly stupid, I cannot fathom a method for accurate and repeatable domino plunges to secure horizontal shelves to a sloping rail. I am thinking story stick rather than measure and mark.
Background - Built in shelving into a small cupboard in roof void. Essentially a square with the top corner cut off (not a triangle!). The 1st and 2nd shelves join the vertical section but shelves 3 and 4 join a 40 degree run, the 5th self is the top and that's not an issue. The shelf spacings are exactly 440mm apart with dividers separating them so any mis measure will show, especially as the shelving is underlit.
To make matters worse, the built in unit will fit snug into the space with a 20mm scribe all around (wiggle room) and the space is narrow with an acute access way so cannot be pre assembled (must be dry fitted, taken apart and re assembled in situ).
Not sure why I thought this was a good idea but hopefully some suggestions will come forward. Many thanks in advance. D

 

[ChuckM]

If I understand your requirements correctly, this is how I'd do it:

[attachimg=1]

The DF is the ideal tool for this kind of angled build.

Please don't forget to plan for the necessary clamping cauls or tools.

 

[DeejayK]

Hi Chuck,
Thanks for your suggestions. That was indeed the initial plan but I need a way to precisely position the rail mortice to ensure shelves are parallel. Unless I am overthinking it? [unsure]

 

[bobtskutter]

I've not got my Domino with me to play with (I'm in the office )

When you're plunging into an angled surface the reference FACE is the top of the board.  So the pivot point of the DF500 fence comes into contact with the top corner.
* make the first mortise into the shelf on the angled surface with the DF500 fence set to rest flat on the top of the shelf.
* set the DF500 so the fence is opened out flat, DO NOT change the depth position of the fence.
* mark the sloping rail where the top of the shelf touches it, then put DF500 on that line. You can use the reference edge on the DF500 fence to align with your mark.

That makes sense in my head, not sure it's that easy to read though - sorry.

Bob

 

[bobtskutter]

Plan B - do a through mortise from the top side of the angled surface then push the domino all the way through.

Bob

 

[ChuckM]

Hi Chuck,
Thanks for your suggestions. That was indeed the initial plan but I need a way to precisely position the rail mortice to ensure shelves are parallel. Unless I am overthinking it? [unsure]

Disclaimer: I'm just thinking aloud and haven't really verified to see if this would work. Can you approach the angled joinery like a typical T-shelving joint? You can use some scrap to check that out:

[attachimg=1]

If it doesn't work out that way, simply mill the mortises on the rail with a straight edge clamped on it to guide/position the Domino Joiner.

 

[Svar]

Assemble the entire piece except the sloping side. Make sure everything is square and parallel. Place the sloping side last and draw lines across edges where dominos would go, continue them onto the face/end grain of the mating pieces. Make mortices.

[attachimg=1]

 

[PaulMarcel]

Maybe I misunderstood, but you mentioned that it must be assembled in place. It sounds like the unit fits into a specific space so I'm wondering how you'll assemble in place when my brain is reading that, due to the confines, you wouldn't be able to get clearance for the Dominos to insert into the mortises.

So as much as I love my Domino and use it for a lot of non-Domino-y things, I think I'd consider two non-Domino ways to handle those sloped shelves...

If the left side of the sloped board is visible and the shelves are reasonably deep (150mm+), I'd cut stopped dados into the sloped sides using a table saw with the blade at 45º then use a slot cutter on a router to make a stopped slot in the angled side of the shelf. Now just take a narrow strip of 1/8"/3mm BB ply and use it as a loose tenon. I've had great results with this and it's easy. But it does require that the shelves be reasonably deep since the stopped dado in the side relies on the table saw blade and won't be able to get as close to the edge as you might like due to the radius. I buy "project boards" of 1/8" BB ply to have around for this.

The second much easier option is if the left side of the sloped board is not visible... Dry fit the shelf in place then drill holes through the outside of the sloped board into the shelf that is held in place. Glue in dowels then flush cut them. This is ridiculously easy.

What I like about these other options is that the tenon/dowel is in shear whereas the Dominos in your diagram are in shear and tension. It seems likely those would gap over time/seasons.

 

[Michael Kellough]

Secure the mitered ends of the shelves with a brad nailer.

Slot the top and bottom of the dividers to pass over Dominos or biscuits.

 

[DeejayK]

Hi All, thanks for the input and expertise you are sharing.
I agree with the numerous suggestions that, ‘to get it done’ one could dry fit, plunge from the outside of the slope in and drive a tenon home which the shelf would pick up again when rebuilt in situ. This will not show when fitted. With the accuracy of modern equipment I hoped for a stop block type approach, similar to when domino’ing mid position shelving with the shelf laid flat.
Great idea for the long loose tenon, have used that when doing scribes around built in’s. Shelves are 50cm wide and with the scribes not fitted around the outside, there will be up to 2 inches/50mm of wiggle room.

Paul, great point. Not for one moment had I considered the loading on the tenon through the shelf. These shelves are melamine covered mfc (left over kitchen carcass material) and so are not light to start with. You would propose a horizontal dowel, drilled in from the outside? I am very nervous of trying to slot the 2300mm rail at 40deg, the 2meter shelf could obviously be laid flat on a router table support or done freehand with a track as guide rail.

Whatever, the eventual placement solution, I now realise I need to incorporate some horizontal connections in the joints somehow.

Thanks again everyone, I have a few more days to ponder due to other commitments but will let you know how I proceed.

 

[ChuckM]

How thick are the mfc boards?

That's a critical piece of info. missing. If it's 3/4", given the width (50cm? per shelf/pocket) and the vertical supports there, the Dominoes alone will hold everything intact for normal loading (mfc is not a concern for wood movement, right? Not familiar with the material).

Zero issues (since March 2021) with this rock-solid Dominoed/knock-down melamine shelving (17mm x 300mm x 610mm; 6mm tenons):

[attachimg=1]

If I was building that angled storage unit, I wouldn't do it any other way but the DF500/loose-tenon, because of ease of execution. (I might add a back board or cross strips to resist racking if the unit was intended for unusually heavy loading such as metal machine parts, etc.)