Be careful not to anger the gods

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lab123

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Mar 22, 2007
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I pre ordered my domino, waited patiently for the release, watched the ups tracking like a hawk, received unit a day early ( quite a surprise).  Unpacked the unit, plugged it into my ct mini dust collector, go to flip the switch, and power goes out for the rest of the night.  Couldn't even heat up my sandwich in the microwave.  All is right with the world today, power is restored and no disappointments with my first festool purchase (so far).  My only concern is that the slot fits so tight on the domino, will there be room for the glue?  Any thoughts?

Lab123
 
What a bummer!  Did turning on the Domino cause the power outage or was that something different? :D :D

I was concerned about room for glue, too.  What I did was to put glue just on the tenon, not in the mortise.  Got a little bit of squeeze out (and thats a good thing), but no hydraulic push back.  A little dab will do you!  By the way, the tenon does have some indentations to capture glue so it won't all squeeze out.
 
Watch the Domino video on the festool web site. They show adding glue to the mortise not the tenon.
 
I don't feel safe putting glue only on the mortise or the tenon...especially with a tight fitting tenon.

I had no problems wetting the mortise (not slopping it in) and then a very light wipe on the tenons.  Glue on both tenon and mortise and no hydro lock.

IMO glue on only one surface when you have a tight fit is a failure waiting to happen.

YMMV
 
OK Bill, but can you prove it? ::) If you can, then there's a lot of us out there that's going to have joints failing. ;D When ever I applied glue to both surfaces, the only thing I noticed was I had more squeeze out. I worked with the inventor of the Katie dovetail jig, Terry Hampton. He told me he talked to Franklin about the what is the best clearance between two mating surfaces. According to Terry, .006 between the two  surfaces to allow for a .006 glue bond. Doesn't make a difference if both surfaces are wet or not. If I'm wrong, or Terry is wrong, please let me know.
 
Les, everything I've ever read about aliphatic resin glues says that you should wet both mating surfaces.  Just because you have a tight mechanical fit doesnt mean that the joint is going to survive wood movement and abuse.  Common sense tells us that for the glue to work it must penetrate both surfaces.  Starving the joint, which IMO can happen when you push a dry tenon into a very tight mortise, makes for less penetration and a weaker joint.

Proof?  I started my statement with IMO and ended it with YMMV.  I'm confident that my joints wont fail because of poor glue adhesion. I'd rather use a little more glue then run that risk. :)

Edit: as far as wetting 2 surfaces, if you can get good penetration by wetting only one then it should work just fine.  What if by the time you get to the last joint it is 15 min...going to get the same amount of penetration on the dry side? I'm not convinced that you can and I don't get hydro lock nor a mess of squeeze out.
 
Qualifications,

What I know about glue's could fill a shot glass. (1/2 true)

What I have in practical and common sense is a truck load.

(slight exaggeration)

Coating both surfaces is not necessary as long as you have adequate glue

on one surface for transfer.

Whether it gets there by wood , brush or bottle makes no matter.

Good bond comes  from the clamping pressure and duration

of clamping time. To short and to long a time are both detrimental.
Yellow glues when clamped correctly, bond at the cellular level.

To this redneck that is pretty intense.

Per
 
Interesting thread.  If I get some time today, I'll rip open the joints I glued yesterday and see it there was penetration into the mortise side.

Bill, had to laugh at the thought of having 15 minutes for glue up.  Out here in New Mexico, with single digit humidity, the open time for PVA is about 4 minutes :o  Complicated glue-ups get pretty dramatic. :D
 
I am probably a bit uninformed about glues, but what is running through my head would be to thin the glue out a bit and put some on both surfaces.

Maybe there's a glue chemistry problem with doing this.  Anyone know?

Loren
 
Some cabinet shops use types of dowels that are "pre glued". They are sprayed with glue  all you have to do is add water, I used a spray bottle, what I found was, it was very hard or next to imposible to apply too much. It was very rare to see "hydro lock" the reason I guess is, water is very thin and can flow out.
Maybe this is the answer we are looking for, and I predict Festool will sell these kind of Dominoes in the future. the only down side is the glue is not water proof.

Mirko
 
Per Swenson said:
Qualifications,
What I know about glue's could fill a shot glass. (1/2 true)
Click to expand...

I've got a lot less experience than you, and probably a lot less common sense as well.  But one time I decided to see what would happen if I edge-glued two pieces of wood, like you'd do for a table top, but only coat one piece with glue.  After a minute of two of clamping time, I took the clamps off and took the two pieces of wood apart.  The amount of glue that was on the second piece of wood was surprisingly little, and it was not distributed very evenly.  So ever since then, I've always followed Franklin's directions and coated both pieces.

Now I'll admit that I didn't do anything further, like re-doing the experiment, but allowing the joint to stay clamped until the glue was cured, and then testing it against another piece that was done the "orthodox" way.  Maybe both would have been just as strong.  Or maybe the experimental joint would have been "strong enough," even if it was not as strong as a typical glued joint.  I've done a few other experiments with simple, butted glue joints, and I'm pretty amazed at the strength of today's white and yellow glues.  Definitely stronger than I was taught 25 years ago, the first time I tried to learn woodworking.

I also have to wonder what would have happened if I had glued only one side, but then moistened the other side with a "wetting agent" (a dilute solution of dish soap and water).  That might have increased the transfer of glue from one surface to the other.  It would be really easy to do with Domino tenons, too--just put a little glue in the mortise, then quickly dip each tenon in a little cup of solution just before insertion.  Yeah, it's extra work, but not much, and if it decreases the risk of joint failure and hydro-lock, then it might--might--be worth it.  Something tells me David Ronyak might be able to contribute a little expertise on this point...not to put him on the spot  ;)

Regards,

John
 
I think you're on to something with the wetting idea John. Wet stuff prefers to migrate to areas that are already wet. Squeeze out follows the path of wetness before it starts spreading to cover the previously dry areas so even if some glue does squeeze toward the dry areas while clamping it often won't be enough to soak into both surfaces enough to form a full strength bond. But, it usually good enough anyway. You may have noticed that the polyurethane glues instruct you to moisten the opposite surface, explicitly to "activate" the glue but I expect it also helps the glue migrate.

I've done crude testing of glue bonds as well and my conclusions are the same as the manufacturers advice - apply a thin even coat to both surfaces. I've learned the hard way that the only true short cut is to follow directions, the manufactures want it to be easy to use their product so deviating from the "instructions" usually has undesirable consequences.

I usually wear disposable nitrile gloves while working and in addition to their other benefits they transform your finger into a great tool for spreading glue. I run an 1/8" bead (depending on the absorption of the material) down a 3/4" surface and spread it out with the nitrile covered finger which tends to leave a thicker coating on the edges of the surface where I don't want so much so I then quickly spread it back to the middle or pickup and transfer to the other surface. It takes less glue than most people think as long as it is evenly spread (unless you are edge gluing MDF which takes much more glue). I keep a damp paper towel nearby to keep my glue trowel in good condition.

 
Hi All,

The technique I use is to coat the walls of the mortise by spinning a solder brush inside the mortise.  Then I put a swipe on both sides of about half a Domino and insert it all the way into the mortise.  By pushing it all the way in any glue that is wiped off of the sides or resides in the bottom of the mortise well will be pushed up the rigged edges of the tenon.  Wipe off any puddle that forms around the tenon and use that to apply to the protruding sides of the tenon.  Spin the brush inside the other half of the mortise and put the joint together.  Since the Domino tenons are 1 to 2mm shorter than the nominal length, the well in the second half of the mortise is plenty big enough to handle any resulting glue wiping off the tenon wall. 

What I found was if I just insert the tenon part way into both mortises and then tried to force the joint closed it is possible for glue in the well to try to come out up the edges of each tenon only to meet at the glue line of the joint where there was no more space for the glue to move causing the hydro lock.  It doesn't happen all the time, but can happen once in a while.  If you follow the technique of inserting the first tenon all the way into the first mortise to the point it bottoms out and then wiping the glue puddle away to put on the walls of the tenon sticking out you eliminate this possibility.

The Dominos tend to be very consistent in size.  They do not swell up the way biscuits do.  I laboriously measured several hundered Dominos from multiple sources one day.  They all were within 0.1mm of the stated thickness and the center of the distribution was right on the stated thickness.  The mortise cutters I have measured appear to be 0.1mm under sized.  With the 5mm Dominos if the cutter is 4.9mm and the Domino happens to be at the upper end of the measured range, then it will be somewhere around 5.1mm in thickness resulting in a 4% interference fit.  That is quite a tight tenon face to mortise wall fit.  Using a 10mm Domino and the same disparity it is only a 2% interference fit which is not overly tight.  In reality I find the 5mm Dominos usually fit tight and the 10mm Dominos rarely fit tight.  The others fall predictably in between. 

The stamped name and ridges on the faces of the Domino appear to be sufficient in depth to overcome any disparity in measured thickness of the Domino so they appear to form a glue well along the mating faces that will hold something like a .004" to .006" glue line which is what most glue manufacturers recommend.  When I was using my industrial slot mortiser and making the loose tenons, .004" to .006" (about 0.1mm) was the fit I was after so this all seems consistent to me. 

Jerry
 
I received my Domino set last week.  My first orientation project was reinforcement of a couple of 5 ft span shelves made of particle board core melamine.  Can you say "sag" even without any load on the shelves?  I decided to see how accurately I could mill all the mortise holes just using the centering marks on the tool, leaving the width of all the mortises on the "tight fit" setting.  Amazing - all eleven mortises on each shelf matched those on the maple reinforcing strip to be added.

I first machined a set of mortises into the edge of a shelf, for the tenons to be inserted parallel to the shelf.  Then I machined the mortises into the maple reinforcement strip.  To my chagrin, I then realized that somehow the vertical fence adjustment had slipped progressively as I went from mortise to mortise, resulting in a nonaligned row.  I simply filled those mortises with dominos.  Then I reset the fence and remachined the mortises.  Because I had not waited long enough for the glue to fully dry, this resulted in gumming up the bit with a glue and sawdust mixture!

I also had a bit of trouble trying to apply the Titebond glue onto the sides of the 5 mm mortises using a solder fux paste brush.  The brushes I have are a bit too large for the 5 mm mortises.  Application of the glue is far more time consuming than laying out and machining the mortises.  Has anyone any ideas how to speed this up while still insuring that all surfaces are wetted with glue?

Also, I learned that particle board core melamine does not have much holding power if those tenons are under tension (due to the bowed shelf).  It's best to position the Domino tenons so they are in shear loading, i.e. with the tenon length parallel to the plane of the shelf.  But the arrangement of one of my shelves did not lend itself to applying the reinforcement strip to the edge because it was contoured around some door trim.

Rick Christopherson,

Thanks for your "pre-release" manual.  I found your tip regarding machining mortises for bookcases very helpful!  Very fast, simple and accurate!  I am looking forward to using this fine tool for many  projects. 

Jerry Work, I am looking forward to your manual.  Any idea when it might be released?

Dave R. 
 
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