The thicks and thins of Dominos

[Flowboy]

Hi all,

Today I performed a very loose, very uncontrolled experiment on the effect of heat on domino width.
I took 10 6x40mm dominos, measured their thickness using a digital micrometer and then moved them to a warmer, but not consistently so, environment.
I also measured the internal width of four 6mm mortices. Two with the Domino cutter width at position #1 and two at position#2.

Results. The dominos at base line measured between 6.01 and 6.08mm. They varied not only between dominos but from end to end of individual dominos.
After 8 hours in the warmer environment, all except one had lessened in thickness, by an average of 2.5% but some up to 4.5%. A stiking example is one which started at 6.06mm at one end and 6.08mm at the other, and reduced to 6.00 and 6.03 after warming.
So I guess what I'm saying is that the issue is related to environmental factors rather than manufacturing. I also suspect that length is affected. This may give rise to the scenario whereby some dominos in a bag may be longer than expected.
I have the data if anyone wants it and shall measure again in the AM.
Interestingly, the internal width of all four mortises measured 6.1mm

Regards,

Rob

[Auld Bassoon]

Hi Rob,

No surprises there methinks, as we get used to the tool, we find these little issues.

The lesson that I'm taking from this is to measure the Dominoes before using them in a critical application, or else build an environmentally controlled (temp, pressure & humidity) box to store them in. Perhaps a tad OTT, but maybe a lamp-box type of affair wouldn't go amiss. Hmmm.

Nice to know the tool is consistent in its cuts though. I must make a mental note to measure some test cuts too. If set to "6.0mm" and it cuts "6.1mm", ie just a poofteenth for clearance, well that's impressive when so repeatable :)

[Powertoolman]

Rob,
The reason why the Dominos shrank when you heated them is because the moisture content was reduced. In a sense, you re-dried them in a kiln (kitchen oven).

If you are getting variability in the Domnio tenon sizes, much of it has to do with how they are being stored. The best way to store the tenons is to keep them in a plastic bag in a dry environment. If you live in a humid climate, the tenons will absorb moisture and swell.

Dominos are not as susceptable to moisture as biscuits, but they will react similarly as any piece of wood will react with changes in moisture.
Rick

[Flowboy]

Hi PTM,
That's exactly what I was trying to prove.

Regards

Rob

[roblane]

apologies for this dimensional diversion but while you're on the subject of size can you tell me exactly how wide dominos are?

looking at any of the global Festool sites doesn't seem to say

background: I have no Domino but the time is very very near :D

I'm trying to work out the placement of multiple dominos per joint in some large hardwood frames I'm involved in building for a conservatory and it's late here in the UK so there's only you good folks to ask.....

thanks!

[nt900]

Hi roblane,

Domino sizes are as follows:
5 x 19 x 30
6 x 20 x 40
8 x 22 x 40
8 x 22 x 50
10 x 24 x 50

See attached images.

What sort of piece or joint do you have in mind, maybe someone here has experience with multiple domino joint placement.

[TassieKiwi]

Roblane

If you can describe or post a pic, Lignum or one of the other DAC club will be sure to offer ideas.

[Greg Q]

Hi all,

... all except one had lessened in thickness, by an average of 2.5% but some up to 4.5%. A striking example is one which started at 6.06mm at one end and 6.08mm at the other, and reduced to 6.00 and 6.03 after warming.



The recruiter said there'd be no maths on the forum, so forgive me if I've got this wrong, but isn't that reduction (0.06 mm) only just 1%?. Also, 0.06 mm is about half the thickness of a sheet of copy paper. Can you detect the gap visually in the joint?

Greg

[Auld Bassoon]

The recruiter said there'd be no maths on the forum, so forgive me if I've got this wrong, but isn't that reduction (0.06 mm) only just 1%?. Also, 0.06 mm is about half the thickness of a sheet of copy paper. Can you detect the gap visually in the joint?

Greg

Short answer Greg, is no. If a Domino "biscuit" is inserted into a Domino cut mortice and then cut flush, all one sees is the colour grain difference between the Beech of the Domino and the surrounding wood.

It's this level of fit that makes even a dry fit up almost as strong as a glued-up one.

Having learnt this lesson, I now (thanks Lignum!) keep a selection of drier Dominoes for dry fits - mainly so as I can get the bugger apart again :)

[Auld Bassoon]

Roblane

If you can describe or post a pic, Lignum or one of the other DAC club will be sure to offer ideas.

In my simple view, the same basic practices apply as with regular loose tenons.

I use a rule of thumb of one tenon to the depth of 20% ~ 30% of stock width, and max 30% stock thickness for the tenon every multiple of three stock widths - ie if tenoning a board 100mm wide and 22mm thick, I'd use 25mm depth mortice, with an 8mm thick tenon (Dominoe) every 300mm.

Because of the Domino's inherent accuracy, and the strength of the Beech 'tenons', it would be resonable to reduce the number of joints involved, but contrarily, because of the ease of use of the tool, it's probably better to increase the joints a little.

For thicker stock, I'd probably go with two rows of Dominoes, alternating their spacing.

Of course, one has to consider timber type, grain orientation, intended use and expected environment.

Very happy to listen and learn from more experienced Domi users ;)

[Greg Q]

Thanks Steve...I thought so. I auditioned the Domino recently...I was very impressed. Very. I need another sander right now, then a Domino's next on my list.

Greg

[Lignum]

I like the ones that are a bit loose. As Steve pointed out i just keep them in a seperate box and use them for dry fitting. This is the first time in my woodworking life that i love dry fitting what im making:D But ist a real bugger when you need to get the pliers out to get a Domi that is a "normal" fit out of the mortice.

[bsrlee]

Sounds like you need to make up a set of 'fit-up' tennons - say, soak them in water, sand to 6mm (or whatever), stain some bright colour & dry. Then you can dry fit the joints knowing that you can get them apart again in future, and being a very different colour, you won't accidentally glue them into the final joint.

As for the shrink & expand problem, just get some screw top plastic storage bottles, dry the tennons out thoroughly & stick them in the bottle with some silica bags/tins & only take out enough to do the job at hand.

Convert the supplied systainer into a tool box for something else.:)

[Flowboy]

Hi all,

I think that putting some sort of seal around the domino systainer is a good alternative, as it means the dominos are being stored in a way whereby they can be in useful quantities. This I felt was a concern for people going on site in a particularly humid day and possibly seeing the fit change over an 8 hour day. That was the other thing, how long does a change take.
The % change was taken as (starting width-final width)/100.
Steve, the fact that the internals were all identical is great, but I'm interested as to why a 6.08mm domino would have a problem in fitting?
Finally, and I think most importantly, I feel that while we all knew there was a change, we didn't know absolutely why. Now we know its atmospheric, that it is variable inter and intra domino and it definitely is not a production/QC issue. Only question I ask is why put them in a systainer without even some silica gel, when they need better protection from the elements?
If I start bringing the domino box inside, it's only a matter of time till the cats start building things!!

Regards,

Rob

[Flowboy]

Hello all Melbourne Dominators,

Hasn't it been nice having all your dominos fit during the recent warm weather? Since the humidity is on the rise again...
(I really just wanted to put a message above the WW Poll one, not that I am belittleing its importance)

Regards

Rob

[Lignum]

Rob, i have noticed the ones that stick are of the flat sawn vatiety and the qtr sawn are never a problem:)

[Rocker]

Surely this is a non-issue; if I notice that a domino is a bit tight to push into its mortice, I just give it a few strokes on some 120-grit sandpaper to remove the extra 0.05 mm that is causing the problem - not more than a few seconds' work. If dominos are made from natural wood, their dimensions are bound to vary slightly, according to the prevailing humidity.

Rocker

[Flowboy]

Hi Lignum and Rocker,

Lignum, thats a fascinating observation at several levels primarily with regard to moisture retention of cross cut v flatsawn timber in general.

Rocker, I guess this thread was an exercise in determining the effect of moisture over a given time frame and the effect on dominos in general. I think we are all aware of the moisture issue and ways to resolve it and I really was being tongue in cheek:D :D .

Regards

Rob