Domino glue up question

[Phil Mueller]

Sorry for the naive question. I borrowed a DF500 to put together a kitchen table for my son...so I’m a first time user. The rails/aprons to leg will be a double tenon. One will be on the exact fit setting and the other on the middle (wiggle room) setting. When glueing up, does the wiggle setting domino need a glue that is gap filling? I do plan to reinforce the legs/aprons with corner blocks. Seems everything I’ve seen just uses regular glue, but....

Thanks!

[Jonathan Jung]

I always use the tight setting for something like this.

[ChrisA Edwards]

I put glue in the mortise and on the dominos and glue. I don't worry about the slight gap in the oversize mortise.

I use the one tight domino for alignment and middle (oversize) setting for all others.

Although with that said, I'm not sure the DF500 will give you a big enough mortise for strength without some other mechanical support in other areas of the table.

[Mike Henderson]

I agree. The strength is in the face glue surface of the domino, not on the sides. Even the tight mortise has a bit of wiggle room on the sides, probably to let glue come up from the bottom (when you put too much glue in the mortise).

So don't worry about the sides, just get glue on the faces of the domino and on the sides of the mortises.

Mike

[Jeff Roltgen]

Two point answer:
- If you haven't already cut them, I'd strongly urge you to run tight for all, using super crisp pencil lines for marking. I do hundreds of joints like this every year with my DF500 for chairs, and everything works fine, every time. In fact, I almost never use the over-size setting in close to a decade of using this tool.
- If you decide to go one tight, one loose, use Weldwood Plastic Resin glue, or similar powdered plastic resin. Absolute best for furniture joints that will take abuse. Epoxy, okay, but plastic resin is just less of a mess, cleans up with water, and squeeze out pops off very nicely.
- Okay, third point, FWIW - if you want to control squeeze-out, use a small brass-piloted chamfer bit around edge of domino holes. Creates a well to trap squeeze out, reducing and practically eliminating squeeze out, regardless glue of choice.

[Phil Mueller]

Thanks all for the quick input! I have only done the one tight fit at this point, so I’ll see how accurate I can get to make them both that way. And yes, I was also concerned that the DF500 might not be a large enough tenon for this, but I didn’t have access to a 700...so plenty of additional mechanical support will be added.

I’ll look into the plastic resin glue...thanks for that input.

[Cliff Polubinsky]

Sat through a Festool demo at the local woodworking store. The Festool rep specifically said that using the wider settings on the Domino doesn't make any difference. The strength comes from the long grain to long grain glue joint. The sides don't add anything important to the joint strength. In fact he said to use tight on one side and wide on the other.

Cliff

[Jeff Roltgen]

The sides don't add anything important to the joint strength

When flexing across faces, like a table-top glue up where the sole purpose is aligning tops of slabs, perhaps.
In the context of chair and table legs, it's wiser to be 100% tight all around, as there's a tremendous amount of pressure exerted at those joints.
Every ounce of glue surface counts, even end-grain.
While I'm sure he's well schooled by Festool, I still feel no need to use over-width mortices, especially considering, it's super easy to align with accurate layout marks, given the accuracy of the tool.
I regularly do so with 5-8 foot long edge joints, 7-10 dominos with no problems.

Have you ever seen over-width mortices advocated in any other instruction for proper mortice and tenon joinery of table and chair legs?

Not I.

[Andrew Hughes]

Jeff why do you use so many dominos for edges on long grain. If your using plastic resin glue or any of the titebond that’s fresh it should be incredibly strong. I’d even wager the joint looses strength as it looses long grain. From so many dominos.

[Greg Quenneville]

I am with you, Jeff. I never understood the assertion that a mechanically tight joint didn’t matter. Last year I made 25 doors and 34 shutters for our new old house, and cut so many 14mm holes that my cutter is now polished like chrome. A couple of thousand, all on the tight setting without problems. I get that using loose dominoes for long grain alignment is fine, just like a biscuit. But for any stile/rail type joint tighter is better. Why else would the gold standard in conventional joinery be the wedged tenon?

[Jeff Roltgen]

Andrew - I shifted suddenly there from traditional M&T joinery to plywood joints. More accurately, I eyeball 12-14" increments. This is instances where I'm applying solid edge to plywood, or ply to ply butt joints.
Simply trying to emphasize the point: if your marks are accurate, wider holes aren't needed, regardless of the count.

I apologize for the inaccuracy!

[Andrew Hughes]

No problem thanks for the reply.
Im a big fan of the Domino I use when I can.