Domino Oops

[Birdhunter]

I’m building a two level coffee table out of black walnut. I attached the legs (18” and 1.75” square) to the rails (34” x 2” high by 1.75” thick). I used my standard method of one mortise narrow and the other medium wide. I didn’t think I needed double mortises.

Wrong! The joints were weak and separated. Fortunately, this happened as I was working on the table and not after it was delivered. I redid a joint using one tenon but with both mortises being narrow. I also pinned the tenons with. brads.

So far, the new joints are solid. Next time, I’ll use double tenons.

 

[jarbroen]

This is a good warning, especially for new Domino users.

I'll do medium width Domino mortise on all but one hole when I'm joining plywood panels or using for alignment when edge joining lumber.  That's a pretty common recommendation by other Festool users/experts.

When I'm building stick frame it's always the tight fit on all mortises.  I built a 36"x72" walnut dining table with slightly splayed 1 3/4"x4 legs and 1 1/2"x2 1/2" aprons.  I used doubled up 10mm tenons wherever was practical.

 

[Birdhunter]

in retrospect, I should have used my Mafell duo Doweler for the thick top rail-to-leg joints using heavy dowels instead of a single tenon. That was a dumb move. The single tenon with two tight mortises would have been my first choice instead of having to redo the joints.

Live, do, and learn!

 

[grbmds]

Thanks for the information. It verifies my feeling since I've owned the Domino; namely, that using the narrowest, fixed slots on all joints may be the strongest. I do sometimes use one small and the rest medium, but it's usually when I'm gluing up boards edge to edge and want to make sure they align properly. In this case, since there are multiple Dominos and there is plenty of strength on the glued edges, strength isn't the issue; alignment only. It's always nice to have some verification of what you do though.

 

[tjbnwi]

Thanks for the information. It verifies my feeling since I've owned the Domino; namely, that using the narrowest, fixed slots on all joints may be the strongest. I do sometimes use one small and the rest medium, but it's usually when I'm gluing up boards edge to edge and want to make sure they align properly. In this case, since there are multiple Dominos and there is plenty of strength on the glued edges, strength isn't the issue; alignment only. It's always nice to have some verification of what you do though.

Use epoxy in the wider mortises if you need the added strength.

Tom

 

[Birdhunter]

The wide to narrow mortises works well for me gluing up panels since the isn’t much stress on the joints. The rails to legs joints do impose a lot of stress on the joints. Just a little bit of looseness will cause the joint to fail.

The paddles on my 500 are not as accurate as just using really accurate pencil marks. As I said above, the Mafell pins are super accurate.

 

[Bernmc]

I also started off using the one narrow-rest-wider method because that's what everyone seemed to do. However, after watching Peter Parfitt's basic domino howto, I switched to just narrow as he does. I can't see many reasons not to now - as long as you can mark a straight line, and reference off the correct faces, it's an accurate tool and there's enough side-to-side play with narrow domino slots to correct any minor misalignments (and I am not an accurate worker).

The only time I use a wider setting is if I'm assembling a (usually poorly planned) box or cabinet where I need to angle one side or back in and I need the extra domino width so slide the panel in.

And the repetitive spacing pins and wings are now useful!

 

[afish]

It might just be me but I always felt the medium slot was a tad too big. Instead of +6mm perhaps +3mm might have been better From my experience any joint misalignment was always very minor less than 1 mm.  If your off by 6mm you are doing something wrong or need to fine tune the machine. 6mm of adjustment seems excessive to me.  So I always use the narrow slot as well and if I run into a situation that a joint is out of alignment I fine tune the domino on a belt or disk sander.  Typically if im careful with layout its not an issue but it only takes a few seconds to swipe a domino across a sander if needed. Of course if you do a lot of domino work then you may want to find different method.  It would have been sweet if instead of 3 pre set widths if Festool could have made the slot adjustment variable perhaps 0 to +10mm with positive click in +1mm increments. Just throwing that out there if festool ever decides to do a redesign. 

 

[grbmds]

Thanks for the information. It verifies my feeling since I've owned the Domino; namely, that using the narrowest, fixed slots on all joints may be the strongest. I do sometimes use one small and the rest medium, but it's usually when I'm gluing up boards edge to edge and want to make sure they align properly. In this case, since there are multiple Dominos and there is plenty of strength on the glued edges, strength isn't the issue; alignment only. It's always nice to have some verification of what you do though.

Use epoxy in the wider mortises if you need the added strength.

Tom

I've always been sort of a "purist" with the Domino. I like the assembly with all slots the same size. Plus, it gives me more satisfaction with a piece because I'm a bit of a perfectionist. I almost never have any alignment problems, even without using the larger slots, as long as I'm patient and I use the correct techniques. Then I don't rely on woodworking for my survival so I can afford to take more time on my work.

 

[Cheese]

I've always been sort of a "purist" with the Domino. I like the assembly with all slots the same size. Plus, it gives me more satisfaction with a piece because I'm a bit of a perfectionist. I almost never have any alignment problems, even without using the larger slots, as long as I'm patient and I use the correct techniques. Then I don't rely on woodworking for my survival so I can afford to take more time on my work.

A big +1 on this statement.  [big grin] [big grin]

A person just has to be careful when marking, aligning & cutting the Domino mortises. I've never had an alignment issue when using the narrow option on every Domino mortise. That includes boards that are 8' long and contain 7-8 Dominos.

I always use the clear plastic cursor for alignment and forget about using the pins/paddles because they can be off by just a little bit.

 

[Michael Kellough]

I think the wider mortise settings are to accommodate the cumulative error that results when using the pins/paddles instead of the cursor. The farther you go without precise registration marks the wider a mortise you need to avoid having to re-mortise. If the tenons aren’t needed for strength using the pins and wider mortises is very efficient.