Domino observation and potential problem

[OrindaDan]

Hi Folks,

I am new to the board and recently purchased a Domino.  In an effort to ease the tight fit between mortise and loose tenon, I further rounded one of the rounded sides of the tenon with sandpaper which made the fit easier.  However, I noticed that if I removed only slightly more material, the fit quickly becomes too loose.  I believe the reason is due to the thickness of the flat cheek of the loose tenon is actually not thick enough to achieve a snug fit within the mortise.  This looseness is evident if one inserts an unmodified tenon obliquely without fully inserting the tenon to test the fit of the cheek to mortise.  This looseness was observed fitting multiple loose tenons in multiple mortises. 

This rather loose fit concerns me as a traditional mortise/tenon fit between the flat wide cheek to mortise should be snug.  It appears the tight fit of the Domino joint is due to the tightness of the rounded sides of the loose tenon against the rounded portion of the mortise.  I am also concerned that the tight fit of the Domino system does not allow enough glue to be applied to achieve a better bond between the flat cheek and the meatier portion of the mortise which is on the loose end to begin with.  Furthermore, in rail/stile construction, if the tight fit of the mortise/tenon within the stile is between the rounded portion of the loose tenon and the rounded portion of the mortise and not between the flat cheek and the meat of the mortise, then the joint is more dependent on end grain adhesion within the stile.  This problem should be less of a concern in the rail.  Could this be the reason the Domino did not test better in the discussion of the article comparing different joints posted earlier?

Has anyone else had similar experiences or did I end up with a too-big bit or too-small loose tenons.  Should I be concerned with these observations?  For now I still round one of the rounded ends of the loose tenon to allow more glue to be applied which is a real PITA.  I may eventually resort to making my own loose tenons or try another tenon supplier.  Any thoughts would be greatly appreciated.

Dan

 

[ROb McGilp]

Welcome OrindaDan,

This suggests that Tezzer's home made tenon design makes even more sense for obtaining structural stability.

Regards,

Rob

 

[Lou Miller]

My experience with Festool dominos is different from yours Dan. Dan, do a simple test. Don't modify the domino at all. Set your tool to make a mortise that is either 6mm or 10mm wider than the domino. This will eliminate the problem of the rounded sections causing the tightness. Now see if you still have fit issues. If so, your bit could possibly be off, or you might even have a bad batch of tenons. My Festool dominos are still very very tight even when the machine is set for a wider mortise. So much so that I stopped using them and now make my own.

 

[Eli]

I've been using only the medium width mortise setting and have had no fit problems.

 

[Mike_Chrest]

I also had problems with Domino's that were too tight. I moved them to the boiler room at work for a week and they shrunk back to a perfect fit( press in / need pliers to remove). I also tried the microwave for a couple of minutes and this also works.
Mike

 

[eweber]

Same here, I have no fit problem

 

[Warrior]

Im with Lou on this one. Check out the thread on American made tuffer tenons in the sals zone.

 

[greg mann]

Hi Folks,

In an effort to ease the tight fit between mortise and loose tenon, I further rounded one of the rounded sides of the tenon with sandpaper which made the fit easier.  However, I noticed that if I removed only slightly more material, the fit quickly becomes too loose.  I believe the reason is due to the thickness of the flat cheek of the loose tenon is actually not thick enough to achieve a snug fit within the mortise. 

I am also concerned that the tight fit of the Domino system does not allow enough glue to be applied to achieve a better bond between the flat cheek and the meatier portion of the mortisewhich is on the loose end to begin with. 

Dan

Dan,

These two statements seem to be in direct contradiction. First you say the cheeck are too loose, followed by concern about the tight fit not allowing enough glue, followed by restating your concern about the loose fit. Am I missing something here? As far as the tight fit on width is concerned, I believe this is somewhat purposeful on Festool's part to guarantee alignment in zero clearance situations. This is also the direction of greatest movement in the Domino as it reacts to moisture. Festool is making these things in one environment and shipping them all over the world where thay are used in all kinds of different environments: Arizona, Washington State, Australia, New Zealand, etc. No wonder Lou's fit better. He makes them to his preference in the same place they are used. If you want to sand the width a little, go ahead, I sometimes do. But I would not worry much about cheek to cheek fit.

 

[OrindaDan]

Greg,

Sorry about the confusion.  The problem I am having is the tightness between the rounded portion of the joint prevents me to apply enough glue for the flat cheeks which have a looser fit and where the strength of a mortise/tenon joint lies.  I find if I apply the usual amount of glue for a typical mortise/tenon joint, the loose tenon would swell even more and I can not insert it at all. 

However, if I remove some material from one of the rounded ends, I can apply the usual amount of glue for a mortise/tenon joint, but the fit of the cheeks is looser than I like.  This leads me to believe the problem about using too much glue in an unmodified tenon is the tight rounded side becomes even more of a problem and prevents me from applying glue to the cheeks where it is more needed.

I hope this explains the problem better and I will try the suggestions made earlier once I have some time back in the shop.  Thanks to all for the help.

Dan

 

[greg mann]

Unless you have an aversion to tapping the domino into the mortice after you apply the glue I don't think there is any reason to worry about the amount of glue on the cheeks causing the tenon to swell too much to allow for assembly. The fit at the rounded ends is essentially a line to line fit at the maximum width of the domino on the maximum width of the mortice. It is not a full fit all along the radius as there are grooves in the radii on the domino. For me, I could care less if this is a tight fit on width, unless I need to take the domino back out for some reason like dry fitting. I will then sand the edges a little to help with dry fitting and I may even need to hit the cheeks as well but I am only talking about .001 or .002. As far as looseness on the cheeks? I don't seem to have that issue. Maybe it is Michigan humidity and will change this winter. Either way, I don't remember much concern about loose cheek fits. I'm not saying you don't have that condition, I am just saying I don't.

Again, I think we are in subjective territory here. Some guys like their M & Ts tighter, some looser. When we each make our own we aim for what we each prefer. In tool and die work one can order press fit dowels or slip fit dowels. I think it is unrealistic for us to expect Festool to do the same in wood and have us all perfectly satisfied regardless of the humidity in which we live. I am not implying that you are actually asking for that. All I am saying is that it only matters if you have a hard time dis-assembling a dry fit. Heck, some guys think it is great that a dry-fit assembly will stay in place and not move even under significant force. Others complain that the dominos are too hard to remove. Can't be both.