Working to close tolerance with wood

[J-G]

Most of today I've been working on my latest clock which has a timber dial and case. The dial is mostly what was sold to me as 'Marble' wood but in fact is some form of Palm which is 'evil' to work but perfect (as far as its appearance is concerned) for this project. It is inset with Ebony, Pink Ivory & Maple - - - viz:

You will see that the Maple (Dots and Battens) are rather small.

In fact the Major Hour markers are 8mm x 3mm, the Minor Hour battens 5mm x 2mm and the Minute Dots 1.6mm Dia.

They are all 2.5mm long (or 'deep' if you wish)

If I had made the Major Hour battens 8.1mm long they would not have fitted the slots - or only 2.9mm wide then they would leave a space.

Similarly, the 'Sun' had to be 24mm dia. - not 23.9 or 24.1.

This is not yet the finished product, the battens & dots are currently glued in but not cured. Once the glue has gone off they will be sanded down level and the whole dial reduced from the current 10.3mm thick to 10mm. There is still a curved slot to be taken out as a 'window' for the day name to show through.

To give a better perspective as far as scale is concerned here is an image of one of the Minute Dots held in Nº5 tweezers (with a 5p piece for scale) :

I doubt that many of you will have applied glue with a scalple but that is what I had to resort to for the dots. Each one was turned to 1.6mm dia. - a length of ~10mm at a time - and sawn to length with a 4/0 jewellers saw.



I'll agree that the beautiful work that @Adam W. creates does not necessarily need to be as precise as my clock dial but if my dial was out of round by 1mm it would most certainly be noticed and detract from its appearance.

If I were to be building a house/shed/workshop - - - even a table or chair - - - then I would be happy to work to within a mm but there are projects which most definitely do need a higher precision.

 

[Fitzroy]

With all made items the relative and the absolute are important. I doubt anybody would argue that a 15mm or 17mm tenon are any use in a 16mm mortise, I bet most mortice and tenon joints are within 0.1mm of each other. However on a 8’x3’ table 1mm is more than accurate enough. Your clock face requires greater accuracy than many items as the human eye is very used to looking at a clock face and would spot a small inaccuracy very quickly.

 

[Daniel2]

It is quite usual to work around a tolerance of 0.10 mm.
What's the issue ?

 

[Jacob]

With all made items the relative and the absolute are important. I doubt anybody would argue that a 15mm or 17mm tenon are any use in a 16mm mortise, I bet any mortice and tenon joints are within 0.1mm of each other.

Exactly.

However on a 8’x3’ table 1mm is more than accurate enough.

Of course.

 

[J-G]

I'd consider easier ways to fit your dots, rather than making them to measure one by one.

????

 

[eribaMotters]

I always thought that with metal you worked to a tolerance. With timber you work to a fit.

Colin

 

[Jacob]

I always thought that with metal you worked to a tolerance. With timber you work to a fit.

Colin

Yes. Well put!

 

[Noel]

I've edited or deleted various parts of this thread. If one or some members want to make personal attacks on others and drag up disagreements from other threads this ain't the place to do it.
Try www.stopgurning.com

This is a one off moderating post. Please do not quote or ref it. Either carry on discussing wood and tolerances or start a thread on sharpening or ballooning or how a Protocol works or something........

 

[Phil Pascoe]

Oh, dear ...
You work to the tolerances the job demands, surely? The practice might be difficult but the theory isn't.

 

[J-G]

Oh, dear ...
You work to the tolerances the job demands, surely? The practice might be difficult but the theory isn't.

That is basically my point. Previous comments have ignored that fact, just suggesting that due to the nature of wood whatever you do it will 'move' so trying to work closer than 1mm is futile, without referencing the phyisical size of the object being made.

You put it more succinctly than I did.

 

[Spectric]

I think @Phil Pascoe has pushed this in the right direction, tolerances are not a simple one rule covers everything as they are three dimensional and often non linear. Wood is just strange compared to metal as I find it often behaves without following any rules, but the one thing that I do find is that the longer or thicker the piece of wood then the more it misbehaves and moves which is supported by the fact that with much smaller workpieces they seem to remain more stable. I would say that taking this further like J-G has with very small components with little mass then the change would be very minimal and therefore if the potential for change is that small then you can work to much tighter tolerances. I reckon that the guy who makes those wonderful aeroplanes would also be able to add to this.

 

[Bojam]

Most of today I've been working on my latest clock which has a timber dial and case. The dial is mostly what was sold to me as 'Marble' wood but in fact is some form of Palm which is 'evil' to work but perfect (as far as its appearance is concerned) for this project.

The wood used in the dial looks exactly like marblewood. The species Zygia racemosa is native here (French Guiana) and is known locally as "bois serpent". What makes you think it isn't in fact that? It is dense and pretty hard. Prone to checking. I have a few boards and bigger blocks on the rack awaiting suitable projects.

 

[Bojam]

Lovely work btw J-G!

 

[J-G]

The wood used in the dial looks exactly like marblewood. The species Zygia racemosa is native here (French Guiana) and is known locally as "bois serpent". What makes you think it isn't in fact that? It is dense and pretty hard. Prone to checking. I have a few boards and bigger blocks on the rack awaiting suitable projects.

Thanks for that afferimation @Bojam - I accepted the description without question when I bought it about 2 years ago but that name didn't return any hits in the Wood Database. It has sat in my store awaiting an opportunity to present itself for a project. When I'd designed the 'African Sunset' concept it became obvious that it would be ideal.

Even Zygia racemosa doesn't feature in the Wood Database, though I have now found a reference to it previously being called Albizia zygia which does get listed but only the ferruginea specie which I have a small lump of called Tanga Tanga. - - - - What a rabbit hole!!!

I hadn't appreciated that it was 'fibrous' and similar in construction to some Black Palmera (Borassus flabellifer) that I also have until I began to cut a slice off the block. I then realized that it must be from some form of Palm.

Thanks for your second comment as well

 

[Bojam]

Even Zygia racemosa doesn't feature in the Wood Database

It does - see Wood Database page here.

More info here also.

It's used a lot by artisans here for small decorative items like boxes or inlays in larger furniture peices. Quite a lot of turned products too like bowls, pens, etc. Not sure what I'm going to with mine. I was given some big blocks by a friend. A while back I came across a high end artisan / artist in Paris who sells pendants made from bois serpent and zebrawood which looks quite similar. Very small and simple peices, finished to a high standard. Selling for upwards of 60 Euros a pop. Food for thought perhaps. Or maybe I'll build some boxes lol.

 

[J-G]

It does - see Wood Database page here.

D'oh!!

I only looked as far as 'Mab...' rather than 'Mar...'

I made quite a few errors when slicing the block up so I now have many quite small offcuts that may well end up as Jewellery, or boxes, just like the Snakewood I also have.

 

[clogs]

love the clock......
having lived in Africa it make me feel good......some good memories......
thanks

 

[Just4Fun]

I always thought that with metal you worked to a tolerance. With timber you work to a fit.

Colin

I can't comment on working with metal but certainly with wood I always work to a fit, so I like this comment. I always try to get an exact fit; a small gap annoys me no matter if it is on a tiny bit of trim or on something like a dovetail on a large box. I am not claiming I never get gaps, just the accuracy I aim for is always the same.

Lately I have been working without measuring anything. I don't really care about actual sizes at all. I just care about proportions and fit.

J-G your comment about applying glue with a scalpel made me smile. I have resorted to a toothpick before now.

 

[Adam W.]

I'd easily notice a 1mm gap on most things that I make, even large things made from green timber which has dried after being assembled.

I hope my work lasts a long time and just because I have a relaxed attitude to verticality and squareness, I wouldn't call the stuff I make rough, but period and place correct and precise to its purpose.

The only time I use a vernier is when I'm adjusting the brakes on the car, thoughbut.

 

[Jacob]

...

The only time I use a vernier is when I'm adjusting the brakes on the car, thoughbut.

I use one whenever I'm machine thicknessing. It's literally very 'handy' in that you can pick it up and work it with one hand and the scale is easy to read, at least on the simpler ones like my Draper, which is also tough enough for a workshop environment, whereas the fancier ones might not survive getting dropped and trodden on etc. Can work to 0.1mm if needs be. Regular check on the output and occasional tweaks of adjustment.