How bad is too big a domino?

[Toller]

I am making a frames out of 13/16" wood 2" wide.  I wanted the longest domino I could get, so I intended to use a 8x50.  Only I installed the wrong cutter and put the 10mm in, not noticing until I was done cutting everything.

So...  is the problem big enough to do something about it (I am not quite sure what I could do, except start over) or should I just ignore it and go on, safe in the knowledge that it isn't a problem?

It is in a pair of benches for my prospective DIL, so i would prefer they not break; but if I have to start over, I am not likely to finish in time to give them to her.  [sad]

 

[Ken Nagrod]

How many did you cut on the 10mm setting and how many to go?

 

[BobKovacs]

13/16" is just over 20mm, so assuming you centered the Dominos, that leaves about 5mm of material above and below the Domino.   If this was a non-structural application (like holding a face frame on a cabinet) it'd probably be no big deal, but since you mentioned that this was for a bench, you may not have enough meat there to keep the Domino from ripping out the side of the piece if it's loaded too heavily.

 

[Jesse Cloud]

Get some 10mm dominoes, cut them to the depth of your mortises.  Glue them in, let the glue dry.  Clean up the face with a handplane or sandpaper.  Then mortise again with the correct cutter.  No problem cutting into the 10mm domino.  I have to confess that I have done this many times  [embarassed] and it is perfectly strong.

 

[Mac]

Get some 10mm dominoes, cut them to the depth of your mortises.  Glue them in, let the glue dry.  Clean up the face with a handplane or sandpaper.  Then mortise again with the correct cutter.  No problem cutting into the 10mm domino.  I have to confess that I have done this many times  [embarassed] and it is perfectly strong.

Clever fix, and so simple! 

 

[Rick Christopherson]

The reason for sizing a tenon to be 1/3 the thickness of the stock is so that you do not create one weak-link in place of another. When the non-mortised material of your stock is thinner than the thickness of your tenon, it becomes the weaker of the members (sort of, because it also has adjacent material to assist in strength). Even though I would not deliberately use a 10 mm tenon in 13/16" material, it is not the end of the world that you have. Leave it be and assemble the components.

My apologies to Jesse, but under these circumstances, inserting a 10mm tenon for the purpose of re-mortising that same location for a thinner tenon is the worst thing you could do in terms of structural integrity. It won't remove the weakness that was already there, and it will compound that weakness by adding one more glue joint to the same location.

 

[Alan m]

i think you should do a test . get 4 scaps and domino 2 together with the 10mm and 2 with the 8mm. let them set over night and try o break them . my suspicion (only that  but would like to hear test results) would be that the 10mm would be plenty strong , maybe not as strong as the 8mm but good enough

 

[Jesse Cloud]

The reason for sizing a tenon to be 1/3 the thickness of the stock is so that you do not create one weak-link in place of another. When the non-mortised material of your stock is thinner than the thickness of your tenon, it becomes the weaker of the members (sort of, because it also has adjacent material to assist in strength). Even though I would not deliberately use a 10 mm tenon in 13/16" material, it is not the end of the world that you have. Leave it be and assemble the components.

My apologies to Jesse, but under these circumstances, inserting a 10mm tenon for the purpose of re-mortising that same location for a thinner tenon is the worst thing you could do in terms of structural integrity. It won't remove the weakness that was already there, and it will compound that weakness by adding one more glue joint to the same location.

Rick and I differ on the structural integrity of the re-mortised joint, but I agree that your situation is "not the end of the world." [wink]

 

[mastercabman]

The reason for sizing a tenon to be 1/3 the thickness of the stock is so that you do not create one weak-link in place of another. When the non-mortised material of your stock is thinner than the thickness of your tenon, it becomes the weaker of the members (sort of, because it also has adjacent material to assist in strength). Even though I would not deliberately use a 10 mm tenon in 13/16" material, it is not the end of the world that you have. Leave it be and assemble the components.

My apologies to Jesse, but under these circumstances, inserting a 10mm tenon for the purpose of re-mortising that same location for a thinner tenon is the worst thing you could do in terms of structural integrity. It won't remove the weakness that was already there, and it will compound that weakness by adding one more glue joint to the same location.

Rick and I differ on the structural integrity of the re-mortised joint, but I agree that your situation is "not the end of the world." [wink]

I love it!!! My favorite quote when i have a problem!!

 

[Wonderwino]

If you cut your mortises on the "narrow" setting, I don't think you have a structural problem.  If you had lots of space around the sides of the tenon, that would weaken the structure.  Of course, that also depends on the species of wood; if it's hardwood, less problems than softwood.

 

[Toller]

Maple, all cut with narrow setting.
I thought of plugging and recutting also, but figured that wouldn't improve the situation; if the plug strengthens the wood, then the domino will also.  Or so it seems to me.

 

[Jesse Cloud]

Maple, all cut with narrow setting.
I thought of plugging and recutting also, but figured that wouldn't improve the situation; if the plug strengthens the wood, then the domino will also.  Or so it seems to me.

I think the issue, if there is one, is that with the original 10mm mortise, there just isn't much wood left between the mortise and the outside of the workpiece.  When the bench gets some sideways racking stress, the tenon will be a big sturdy lever pressing against a thin wall.  If you go back to the tests Fine Woodworking did a year or so ago on strength of different joints, mortise and tenon (and domino) often failed by breaking the wall left by the mortise.  The glued in remortised plug makes for a thicker wall, and the glue will be stronger than the wood.  If this was a shop bench, I wouldn't think twice about leaving the 10mm in there, but for a "prospective daughter in law" I might go the extra distance.

Also, I kind of feel like we are shooting in the dark, not having seen the details of the joinery.  Is there room to just cut a new mortise?