Glueing Dominoes or loose tenons

Re: Glueing Dominoes or loose tenons

Jesse Cloud

Given the very close fit of the dominoes, I go a little thinner with the glue than I would with other tenons.

In any case, give your dominoes a little tap to ensure they are fully set before cleaning out any squeeze out. If the tenon is setting in a pool of glue, it may wind up sticking out too far for tight assembly later on.

I have never had a domino fail due to lack of glue.

Re: Glueing Dominoes or loose tenons

Jim Dillon

Barry, as Jesse said, due to the tight fit of the Domino I apply a thin coat to both mortises and Domino using a cut-off solder brush. Haven't had a failure yet. Jim

Re: Glueing Dominoes or loose tenons

William Duffield

I usually glue dominos the same way as Jim, both surfaces lightly with an acid brush. However, on at least two occasions, I've put shop projects together with dominos and no glue at all. My router table and K-body clamp rack show no signs of coming apart after several years.

Thanks, that's reassuring...

Barry Irby

I will continue my practice of coating all the surfaces.

William, I hope your clamp rack does not look anything like mine. You are just waiting for the next earth quake.

To make this more interesting,

Barry Irby

I am assembling chairs, made of oak. I don't have huge experience with the Domino and was a little skeptical of the size of the ones I have. They appeared too narrow and I don't have room for two so I cut all the mortises with the machine set on the wide setting and made dominoes to match out of the same oak.

I am concerned the Dominoes are a tiny amount two thick. Considering drying them in the oven or a light hand pass over a piece of coarse sandpaper, or tamping them down a bit on an anvil.

Most useful thing I learned in the Headley shop

Bill Tindall, E.Tn.

A proper fit joint can be assembled with hand pressure.

This tolerance not only ensures no disasters of locked up or broken joints during assembly, it also ensure the optimum amount of glue in the joint.

The other essential element of gluing is that both surfaces must be wet by the glue to make a bond. Either wet one and with proper technique rely on transfer to the other, or coat both and get it assembled before the surface begins to dry.

One of the other things was reinforced by working in this shop was optimum glue application. I have not had to deal with squeeze out for a slid together joint (M&T, dovetail) in many years. Learn to avoid it. Those that suggested trimmed "acid brushes" have learned this wisdom.

Re: Most useful thing I learned in the Headley sho

Barry Irby

I have seen your discussions on glue ups before. And have heeded the advice. Not quite as frugal with the glue as you are, but much better than I used to be.

I find with the Dominoes things change. Not only are end grain mortises different from side grain ones they change in a few hours. I spent a lot of time getting the Performax set to exactly the right thickness and sanded enough stock to make about a hundred fifty dominoes. Cut them down to length and left them sitting on the counter until the next day. Some that were just right are now too snug and some that were a tiny bit loose are now better. I am guessing that the stock changed by exchanging moisture with the atmosphere during the night. The shop is unconditioned and it's starting to rain. The stock for the Dominoes was stored in a conditioned space. Not a real problem, just interesting.

One failure that I've seen

GolfSteve in Calgary

For what it's worth, I have seen domino glue failures in chairs I bought from an Amish Furniture place, manufactured in Indiana.

The problem was three-fold:

First the design put a lot of stress on the seat apron to leg joint.

Second the builder put only a single domino in a 3 inch wide apron. There was room for at least two, and maybe three dominoes. A single three-quarter inch wide tenon for a structural joint was inadequate. The mortise was also cut using the "wide" setting, so there was a gap on each side of the domino, providing even less support.

Third, the joints failed only weeks after the chairs were bought because the glue joints were dry. When I took the chairs apart, it appeared that a bit of glue had been smeared on the domino and none in the mortise. A light tap with a mallet on the domino stub would break the glue bond, and I could pull the domino out.

So, don't do what these guys did. Design for strength, use the maximum domino surface area that you can (multiple dominoes), and ensure adequate glue coverage.

When I use dominoes I spread glue on both the mortise and the tenon. For larger glue-ups I have to have my wife help my to speed up the application time.

Re: Glueing Dominoes or loose tenons

Jesse Cloud

When I was taught woodworking in the Santa Fe Community College, a little squeeze out was ok in the Intro class, but after you had completed a few classes the instructors expected you to know how to apply ample glue with no squeeze out.

And they always expected glue on both the tenon and the mortise.

Only exception I ever make is with veneer.

On a new type of project I've never done before, e.g. a new chair design, I always make a prototype. I never glue up the prototype and have always been able to lift the chair by the bottom of one leg and shake it around with no loosening of the joint. I never use the wide mortise option on furniture.

Re: Glueing Dominoes or loose tenons

Steve Elliott

Domino tenons are engineered in a way other loose tenons aren't. The sides of the tenons are slightly corrugated, which allows glue to be forced up along the sides if the right amount of glue is put into the mortise.

When gluing up I start by putting glue into the part of the joint which will have grain surfaces at 90 degrees. This is the side of the joint which will have the greater chance of failure and which also has a tighter fit. By pooling a little glue at the bottom, I can drive the tenon home with a mallet and keep tapping until I see glue starting to ooze out at the surface in all the tiny corrugations. If there is too much squeeze-out I can remove it before completing the assembly of the joint.

For good measure I do put a little glue at the top of the mortise and on the end of the tenon before inserting the tenon, using an acid brush. Those two bits of glue get spread over the sides of the mortise and the sides of the tenon when the tenon is tapped into place.

Since Domino machines have three settings for mortise width, using either the exact width setting or the middle setting for a little lateral leeway is better for this technique.

For the second part of the glue-up (the stronger part of the joint where the grain is parallel on both surfaces) the pooling technique doesn't work very well because the tenon is shorter than the mortise. It's hard to know how much glue would be necessary and tenon insertion can't be stopped at just the right point. But since the grain orientation is favorable that part of the joint is plenty strong anyway. I add glue liberally to the mortise because it won't show up as squeeze-out. On the tenon a little glue at the leading end is enough to coat the tenon. If I get a few little pin-heads of glue squeezing out I leave them till they're set and remove them with a chisel.

Re: Glueing Dominoes or loose tenons

William Duffield

Further, you are never going to get a strong glue surface between the bottom of the mortise and the end of the tenon (unless you are using epoxy) because the Domino cuts the bottom of the mortise slightly concave (dished), and not flat.

Thanks, lots of help here...

Barry Irby

I agree with Steve. Other than squeeze out, there is not advantage to starving the joint or taking the risk of starving it.

I made a Domino mortise and cut it apart to see what was going on. The bottom is slightly rounded. Dished. This could be a little reservoir for excess glue.

As far as the setting goes....I used the widest setting because I did not like the looks of a single domino and did not have room for two. So I used the widest setting and made dominoes out of the same oak and fiddled with them until I got a very accurate fit. I even considered radiusing the ends slightly to match the profile of the bottom of the mortise, but sanity prevailed.

I have assembled two of the chairs and the one that is fully cured and out of the clamps seems very solid and true.

Thanks for the help. I tried to discuss this more fully along the way but ran into computer issues.