Domino placement/quantity advice

[Naildrivingman]

I assembled a table top last night and upon glue-up, I had some of the edges out of plane. The top measures 24" x 42". The boards run the short dimension. I used 3 8mm x 40mm dominos per seam. I spaced the dominos at 4", 12" & 20". Should I have added an additional domino or should I have used a spacing more along the lines of 2", 12" & 22"?  The difference in plane is less than 1/32" and can easily be flattened with my Rotex 150. I just don't want to make the same mistake twice.

Thanks,
Chris.

 

[Rob-GB]

I tend to keep the domino's between 1" and 2" in from the edge unless a later moulding will impact them and between 4" and 6" on centre on panel/table top glue ups. Sometimes boards need some attention from a block of wood and a hammer during cramping if it slides a bit on the glue.
Alternating cramps from one side of the board to the other also helps minimise creep or introducing a bow into the panel.

Rob.

 

[Stone Message]

Domino joints has a bit of wiggle room Rob-GB implies. I know that where I to join a pair boards then I could encourage about 1.5 mm of movement between the boards along the long jointed edge and probably just over 0.5 mm across thickness.

To make an adjust along the length I would use a single long clamp and either use it at a slight angle so that it moves one piece relative to the other or I would give one end a good hit with a soft face hammer.

To make the adjust to get the two boards in the same plane I would use a Bessey clamp at each end evenly across the joint. If there is some misalignment in the middle of the board then I would try and use some thick blocks of hard wood, one each side, (oak would do) and clamp these at both ends so that they apply the flattening effect over the joint. If this appear ineffective putting a short 3 mm thick slither on each side across the joint will create more pressure at the centre of the thick blocks.

Peter

 

[Naildrivingman]

Thanks Rob and Peter for your replies.

I think the main culprit was the camber of a few boards. I did give a little convincing with a rubber mallet, but the variance returned. Unfortunately I did not have any c clamps or the like to apply mating tension, but I will in the future. I did have alternating clamps to minimize overall cupping of the piece.

I have to admit that I am probably too frugal for my own good, but if extra dominos would make the difference, I need to temper my frugality to match my expectations. As it stands I used 48 dominos for the task and an additional 12 wouldn't break the bank. Luckily the finished product needs to be 3/4" and I thickness planed the material to 13/16, so I have a little grace there.  I will defininitely move my dominos closer to the edge in the future.

Until next time, kind regards from this side of the pond.

Chris

 

[Birdhunter]

Rob's technique is how I do Domino joints. I space 1-2 inches from the edges and then spaced every 4-6 inches. If you are exceedingly frugal, buy the long tenons in bulk and cut them to whatever length you need.

I usually butt the ends of a glue-up against a straight edge to ensure accurate alignment. I use a jointer and a planer to flatten the boards before assembly. Extreme care using the Domino usually results in a near perfect joint.

 

[Rob-GB]

I thought I ought to expand on my reasoning for the spacing of domino's just briefly.
The thinner the board the closer the spacing to counter any flex in the timber. The upside of that is the thinner the boards the smaller the domino's and the more you get in a pack. [big grin]
On tricky glue ups another trick is to do the initial cramping and if the ends are being awkward place a cramp at 90° to the face of the panel on each end, nip it up then encourage the alignment with said hammer and block of wood and tighten up further. Takes a few minutes longer glueing up but saves time, sandpaper and electric later.

Placement of, and sizing of domino's for a project is a bit of educated trial and error. It also helps if the client is getting the bill for them  [wink] I try to use domino's that are in the region of 1/4 to 1/3 the thickness of the pieces being joined and if I have no domino in that range for thicker timbers I consider doubling up (one above the other with at least 3/8" (9mm) between or staggered upper and lower domino's. (again it helps make that choice if someone else foots the bill, I am very aware that home woodworkers don't always have a budget as great as their desire to make something for their family, it is why a lot of my projects use free or surplus materials.)

Rob.

 

[Tezzer]

Rob, you should think about making your own Dominos out of scrap. It's quick and easy and saves a heap of money.

 

[Naildrivingman]

Rob, you should think about making your own Dominos out of scrap. It's quick and easy and saves a heap of money.

Terry brings up an interesting point. I wonder how much better (if at all) that a domino made from similar material as the pieces being mated, would perform. It stands to reason that a same/similar joint would be more homogeneous than using beech or sipo (hardwoods) with pine (softwood).  Then one may ask if a same/same joint is even better.

I'm guessing that Festool has done enough research to reveal that the two species selected as tenons are either the most universal or the most cost effective or both.

 

[Stone Message]

Hi Chris

The are pros and cons to making your own.

Yes, they are easy to make and you can have a little production line to do them quite quickly.

Having them of the same species is no big deal as their grain direction will not be the same as the wood into which they fit (most of the time) and so their behaviour would not be identical to the adjacent wood. They would however blend in if parts had to be exposed.

Festool dominos are compressed and have a pattern that allows glue to travel over the surface. I made some extra wide tenons for a garden gate and did not allow enough space for the glue - the hydraulic locking was almost a catastrophe. I would prefer my dominos to be as strong or stronger than the wood that they are going into.

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Peter

 

[Rob-GB]

I have done but tend to only make them for decorative effect like:-

Thread here

Or for this latch

Thread here

That thread actually has a pic of how I sometimes clamp the board ends, although in this case it is supposed to be curved.

Rob.

edit- [member=11196]Peter Parfitt[/member] you can reduce hydraulicing by scratching the domino with a piece of coarse hacksaw blade, scratch stock style.

 

[Tezzer]

Festool dominos are compressed and have a pattern that allows glue to travel over the surface. I made some extra wide tenons for a garden gate and did not allow enough space for the glue - the hydraulic locking was almost a catastrophe. I would prefer my dominos to be as strong or stronger than the wood that they are going into.

Peter

Peter depending on the application I will pop some home made domino's into the jaws of an engineers vice and give it a 1/4 turn to compress and add indentations for glue. Works a treat and is quick.

 

[Tezzer]

Rob-GB that latch is outstanding. Excellent bit of lateral thinking