How many dominos to use on table top ?

[Intex]

I am gluing up 5 pcs of oak, for a tabletop 2 76/8" thick and 40" long x 40" wide .
Should i put in one row of 10mm dominos in the center of the thickness, every foot or so, or two rows ?
I am mainily using these to aid in glue up and get  all boards flush on top and bottom??
Just received my new 500 and have never used it before

Also have 4 pcs that will only be 18" long.

Thank you!

 

[sancho57]

Id just placed them evenly spaced across the joint.

 

[Birdhunter]

For what you are doing, One row of tenons spaced every foot should work as long as your boards are flat and not warped.

My experience is to glue up boards in twos, then glue the middle board to one of the glued up pairs, and then to glue up the remaining pieces. This approach takes a lot of the "drama" out of a glue up.

I would highly recommend practicing on some scrap before tackling your nice wood. Halfinchshy and Peter Parfitt have excellent Domino videos.

I'm unsure how to interpret your comment about 4 boards being 18" long. Are you trying to join them end to end to use on the table top?

 

[Intex]

Birdhunter:
I was told by someone that for the 40" long 3" thick board use TWO rows of dominos, but so far everyone has said just one row.

For the 18" long x 3" thick boards I use as the face, I was thinking maybe of using 1 row, since it isnt very long of a glue joint?

My question was more , if I need two rows or just one row

 

[thudchkr]

As long as you are gluing face grain to face grain, and not to end grain, the dominos are not needed for strength.  That is why you only need a single row of dominos.  Their function will primarily be to help align your boards and provide little to no additional strength to your joint.  This assumes you have straight clean surfaces that are being glued together.

 

[Intex]

I am gluing up 5 boards approx 8" wide each to make the table top, so I will NOT be gluing face to face, but rather EDGE TO EDGE.

Will I need 2 rows?

Also my domino only adjusts to about 30mm (1.1") so if its single row, i will not be in the middle, unless I am missing a way to make it in the center??

 

[Svar]

Will I need 2 rows?

No. One row. Does not matter is they are in the middle, it's for alignment only.
I typically don't use any tenons at all when glueing table tops.

 

[ChuckM]

One single row of 4 to 5 (max) dominoes since the boards at 40" are not long.

 

[Intex]

Thank you everyone, I will use one row, not centered on the thickness

 

[rmhinden]

Thank you everyone, I will use one row, not centered on the thickness

One thing to add.  See the supplemental manual on the Festool site:

Domino DF 500 Supplemental Manual

It describes what you are doing, see page 13.

Bob

 

[Birdhunter]

The key is if you are gluing boards long grain to long grain, the glue joints are almost always very strong. Gluing end grain to end grain or end grain to long grain produces very weak joins and you need mechanical (tenons) supplements.

I'd strongly suggest laying the boards out on a flat surface as they would lie once glued up and verify 1. they lie flat (don't rock or curl) 2. that the joints almost disappear when clamped together and 3. you like how they look together.

If 1. and 2. are not right, your glue up will be a nightmare.

 

[Intex]

Thanks again, I will let you know how it turns out
Just waiting for a new jointer to arrive so I can joint them edges before glue up
I wii
lol take the suggestion to glue up 2 then another 2 then add 1 to one set then add the 3 to the 2 = 5 boards
First time I’ve worked with this heavy of boards, each about 25 lbs

 

[Birdhunter]

Jointer good, but also need a planer.

 

[Gregor]

Just waiting for a new jointer to arrive so I can joint them edges before glue up

There's the trick to put them flat ontop of each other (upper sides touching, seam where the glueup will happen aligned) - then one cut with the tracksaw to both of them at the same time, cleaning up the seam. Will give a perfectly closed glueup, even with the blade at a sligh tilt as the angle will be identical on both pieces so any deviation from 90° will cancel itself out after flipping the top piece over. Sharp blade and the cut shouldn't need any further processing, except glue and clamps.

 

[Intex]

Just bot a de Walt 735 for 5his job. I was surprised at the clean surface it left on the faces of 5he 3” thick boards. I thought the weight would cause a problem but none so far

 

[Stone Message]

I am gluing up 5 pcs of oak, for a tabletop 2 76/8" thick and 40" long x 40" wide .
Should i put in one row of 10mm dominos in the center of the thickness, every foot or so, or two rows ?
I am mainily using these to aid in glue up and get  all boards flush on top and bottom??
Just received my new 500 and have never used it before

Also have 4 pcs that will only be 18" long.

Thank you!

If you have jointed your boards accurately so that they have square edges which are flat then the purpose of the domino is not structural but for alignment only. The glue will do the rest. Let me explain in more detail...

The concern is probably because you expect the boards to move in some way. Even well seasoned boards will move across the grain through the seasons and your fixing of the top to the legs/frame should take this into account. Dominos or biscuits will not stop this. If your boards decide to twist due to poor seasoning before machining square then all the dominos in the world will not stop that and you also run the risk of the piece failing, not at the glue joint but at some other part of the structure.

The key thing to remember is that you must not apply glue to the dominos (or biscuits). If you do this then movement across the grain (which will happen) can cause the joint to fail. This happens because the glue in the domino prevents free expansion and contraction along the region of the joints. The dominos do not expand and contract along their length and so will have to try and move relative to the wood that they are in. Better to let them do this by not having any glue there.

The type of glue for the long glue joints is also important. I am rusty on the argument for this but my woodworking guru is adamant that Cascamite or similar urea/formaldehyde resin glue should be used rather than PVA. When gluing up a large top, made of several pieces, PVA can start to bond whereas Cascamite will give up to 3 hours of wiggle time. There are other reasons which I hope an experienced professional on the FOG can add to this. One of these will be that the excess glue is easy to remove after it has gone off and does not stain the wood.

I have recently made a large dining table with matching benches from solid oak and explain most of the above in the video.


Good luck.

EDIT: I forgot to answer the question - I used 4 or 5 biscuits across a 2200 mm long joint.

Peter

 

[Mario Turcot]

If you have jointed your boards accurately so that they have square edges which are flat then the purpose of the domino is not structural but for alignment only. The glue will do the rest. Let me explain in more detail...

Peter nailed it.

Since it's for alignment and not for structural support (unless you plan to put some heavy stuff on the table top) only put a few dominos. Make sure to have one side mortises on the tight position and the opposite on medium. I would also try to not align the dominos all at the same distances (from one glue up to another), even if they are 8" wide.

 

[Svar]

The key thing to remember is that you must not apply glue to the dominos (or biscuits). If you do this then movement across the grain (which will happen) can cause the joint to fail.

No. Dominos or biscuits are too short to to noticeably interfere with seasonal movement. Think of all regular mortise and tenon joints, dovetails, etc. Do they fail because they are glued cross grain?
Most people glue dominos in panels, some don't. Does not make any difference.

 

[ChuckM]

The key thing to remember is that you must not apply glue to the dominos (or biscuits). If you do this then movement across the grain (which will happen) can cause the joint to fail.

No. Dominos or biscuits are too short to to noticeably interfere with seasonal movement. Think of all regular mortise and tenon joints, dovetails, etc. Do they fail because they are glued cross grain?
Most people glue dominos in panels, some don't. Does not make any difference.

Svar is correct in the case of a long-grain to long-grain edge joint as posed by the OP. Using a wood movement chart and 6% for moisture content fluctuation, I worked out that a 20mm wide domino would move about 0.009" to 0.018".

I have never used dominoes (close to 1,000 of them) without glue, even when the purpose was for alignment. (The MC in my location is even lower at 2% - 3%.)

It'd be a different story if the OP was doing breadboard ends to a tabletop.

 

[butzla]

None.

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