Knockdown bookcases with Domino connectors: how many to a joint?

[Stan Tillinghast]

My wife wants some bookshelves for our overflow collection. I want them to be knock-down for potential move, plan to use Domino connectors.
If about 11 1/2 inches deep, do I use 2 connectors with a regular(unglued) domino in the middle of each joint, or is that overkill?
If I were doing full depth cabinets, that's what I would use, as I understand it.

 

[squall_line]

There's some good discussion in this thread:
https://www.festoolownersgroup.com/...-sys-d8-knockdown-hardware-auxiliary-manuals/

Along with a video from Peter Parfitt, which have almost never let me down.

There is also a PDF manual for the connector set on the Festool website:https://www.festoolusa.com/service/owners-manuals#DOMINOJoiners

 

[grobkuschelig]

I usually use two, to ensure the edges are tight front and back. If you intent to build for a little more weight, I would suggest either 2 or 3 wooden dominoes in addition…

Depending on shelf depth.

 

[Packard]

I found this online (but no data about holding strength): https://festoolcdn.azureedge.net/pr...ment/542c4d5d-40da-11e9-80f9-005056b31774.pdf

Only suitable for connecting wood or wood-like materials for
furniture construction (no lightweight construction materials).
The Domino connector is only a connecting element and not a
supporting element. Observe the minimum routing depths and
edge clearances. Use indoors only.

Compare with Lamello's site where they give full specifications for the strength of their connectors.https://www.lamello.com/product/p-system-verbinder/clamex-p-14/

They list 80 - 90 Kg tensile for MDF and Particle board.

 

[Stan Tillinghast]

Thank you for the help.
I will be using plywood not MDF.
I did view (again) Peter Parfitt’s video on the connectors.

 

[Cheese]

If this were my project...I'd use  a Domino on each side of the shelf on the rear and a Domino on each side of the shelf on the front. In the middle of the shelf on both sides I'd install a KV-D8.

This allows the shelf load & any structural twisting load to be carried by the Dominos while the KV-D8 connector continues to pull all of the elements together.

So, interestingly enough this is Festool's take on the situation. A vertical span being attached to a horizontal span in both cases...a KV-D8 vs a SV-D14.

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My thoughts are that the increased loading on the "big knock-down stuff" demands more Dominos to be used while the superior strength of the SV-D14 connector allows the use of only one connector.

The KV-D8 on the other hand is relatively stout for the lighter loads that it see's, thus you only need a single Domino to support the structure...however, I'd still use 2 Domino's and 1 KV-D8 on my project.  [smile]

 

[squall_line]

I second [member=44099]Cheese[/member] on this; both versions show a total of 3 mortises: two connectors and one domino for the smaller connectors, one connectors and two dominoes for the big connector.

 

[cpw]

I would try for at least 2 regular wooden dominos.  The wood dominos can pick up the vertical load very well; so that way the knockdown connector only needs to hold things together instead of also supporting the shelf.

Books are heavy, so I don't think there is such a thing as overdoing the support here and the wood dominos are not that expensive.  It is also important to consider sag calculations for the span you want to cover.

 

[Packard]

I looked for, but could not find any published specs on the tensile of the Domino fasteners.  They are quite specific that it is not to be used as a structural member, so shear strength would not be published.

Lamello also does not publish shear strength and my guess is that they do not consider it a structural member either.  But they do publish the tensile (pull-out) strength. 

Aside from that, the dominoes, like biscuits are made from compressed wood (birch?) that absorbs moisture and swells to tighten the joints.  For a bookcase that might be knocked down at some future date, the absorption of moisture (from the atmosphere) might swell the dominoes sufficiently to prevent removal, even in the absence of glue.

Does Festool make plastic versions of the dominoes to use in that situation?

 

[Cheese]

For a bookcase that might be knocked down at some future date, the absorption of moisture (from the atmosphere) might swell the dominoes sufficiently to prevent removal, even in the absence of glue.

Does Festool make plastic versions of the dominoes to use in that situation?

If that humidity absorption issue is a problem, and it may very well be as we've all read that some folks microwave their Domino's before assembly, then these could be an alternative.

I used 10mm x 20mm 6061 aluminum flat to fit into 10mm x 24mm Domino mortises. The aluminum was a real nice firm fit but the aluminum Domino's could still be removed by hand. They were installed into one side of a walnut countertop & epoxied in place.

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[Packard]

I made some "backroom" fixtures for my picture framing business about 25 years ago.  I needed storage for mat boards.  I built boxes with dado slots top and bottom that was a little over 1/4" wide.  I had a little over 12 feet of cabinets for the mat boards and the slots were 2 or 3 inches on center.  I slid 1/4"  thick masonite in the slots to hold the mat boards vertical and to divide by color. 

After about one year none of the masonite sheets were removable.  The humidity had either swelled the masonite or the particleboard and even using a vise-grip pliers, I could not pull the masonite out.

The masonite and the particleboard were not engineered to swell like the dominoes are, and yet they did and became as fused as if I had used glue.

The aluminum blocks look like a viable option, though an extrusion or a die casting would be less expensive. 

In any case, I would not guarantee that the bookshelf would be able to be disassembled.  Perhaps a light coat of shellac (Sealcoat) would prevent the swelling.  That would be cheaper than the aluminum blocks.

This is not my unit, but is typical of the type of case that I built.  I kept the masonite sheets spaced closer to  the boards would not develop a bow.