Info on London-style dovetails wanted

[Jacob]

Looks like a rural piece, and the tradesman was cutting down on time. The iron nail is a nice touch, looks horrible overall but functional. Doesn't look that old to me either.

Was old. Well 150 years at least I'd guess. Possibly a lot older. The back boards were rip sawn by hand - looked like they'd been scratched by bears. Everything hand done, no sign of machine marks anywhere. Adze type marks , more likely a heavy cambered plane, on fronts of back boards. Fronts of front boards still showing hand plane marks from fine cambered plane done in very neat parallel passes, just visible in the right light. The most modern thing about it was the nails!
I wouldn't say it looked "horrible" at all. I really admire this sort of practical woodwork. Nothing "rural" about it either - "country furniture" is a bit of a myth; you'd find the same sort of stuff made in towns, but in the backwoods things get left behind and change is slower.

 

[mtr1]

Just a taste thing, looks horrible to me(the dovetail).

Was old. Well 150 years at least I'd guess. Possibly a lot older. The back boards were rip sawn by hand - looked like they'd been scratched by bears. Everything hand done, no sign of machine marks anywhere. Adze type marks , more likely a heavy cambered plane, on fronts of back boards. Fronts of front boards still showing hand plane marks from fine cambered plane done in very neat parallel passes, just visible in the right light. The most modern thing about it was the nails!
I wouldn't say it looked "horrible" at all. I really admire this sort of practical woodwork. Nothing "rural" about it either - "country furniture" is a bit of a myth; you'd find the same sort of stuff made in towns, but in the backwoods things get left behind and change is slower.

The drawer doesn't look like its had much use imho, and the fact that its hand made despite its late age points to a rural piece. In the backwoods things get left behind and change is slower after all. French rural pieces tend to be a bit more rustic(look older) than an English piece which is probably what threw you.

 

[Jacob]

I did actually see this piece, inside and out. You didn't. I'm not thrown at all!

 

[Benchwayze]

In carcasses, I like to see asymmetrical dovetails, a'la Krenov. For drawers I like Jacob's layout, but there's nothing wrong with having a large dovetail in the middle, or say between every other smaller tail. More gluing area I would say!

Just to be different though I think 'London dovetails' were what some folk call 'proud' dovetails, as found in some Arts and Crafts work, but I could be wrong. 8)

As for two dovetails v one, my old mentor said one dovetail was strongest. More side grain for gluing, but it just didn't look so nice. He could have been wrong too! :wink:

(FWIW!)

John

 

[Racers]

Hi,

Well the amount wood between *London* dovetails is so little you can probbaly ignore it, so it's just one big one.


Pete

 

[János]

Hello,

Strength of dovetails was researched in the XXth century systematically. The strength of a dovetail joint depends mostly on the angle of the tails and pins. An angle between 14 and 18 deg gives the most strength… For sliding dovetails an angle of 20~22 gives the most strength. No coincidence that most machine cut (routed) dovetails were/are made with 14 degree pins and tails… So Jacob’s higher angles would result in stronger joints.

There are methods to determine the strongest possible layout for carcass dovetails, but the resulting pattern is not too nice, resembling the machine cut joints, as the resulting pins are quite wide, nearly as wide as the tails.

But for practical purposes, like craft work, the difference does not count. Almost any arrangement would provide adequate strength for use in furniture. I seldom use dovetail pins narrower than 5mm at the base, and do make them with an approximately 1/9 slope. In very soft woods I change the slope to 1/6.

On traditional Japanese furniture, the drawers were made wit rabbets and rice paste as an adhesive, plus a few nails. This very crude construction was used even on high class pieces. And they held up quite well.

Bye,

János

 

[Jacob]

....The strength of a dovetail joint depends mostly on the angle of the tails and pins. An angle between 14 and 18 deg gives the most strength…

Depends on the glue of course, or a zero angle box joint would not work. And on the size of the pins. Thin pins could snap off

There are methods to determine the strongest possible layout for carcass dovetails, but the resulting pattern is not too nice, resembling the machine cut joints, as the resulting pins are quite wide, nearly as wide as the tails.

As is done for max strength on ammo boxes, water tanks etc. Pins and tails about the same size

But for practical purposes, like craft work, the difference does not count. Almost any arrangement would provide adequate strength for use in furniture. I seldom use dovetail pins narrower than 5mm at the base, and do make them with an approximately 1/9 slope. In very soft woods I change the slope to 1/6.

I quite like steeper angle and single kerfs making little triangles, just for the visual effect

On traditional Japanese furniture, the drawers were made wit rabbets and rice paste as an adhesive, plus a few nails. This very crude construction was used even on high class pieces. And they held up quite well.

Bye,

János

The Welsh used nails too, in this example at least (about 90years old)
The bottom is set in between the sides and everything nailed, including the false front.

 

[Benchwayze]

I would say that the strength gained from slope of the dovetail, is only relevant when force is applied against the slope itself. (As in the front of a drawer, when the drawer is being opened)

If you apply force to the side of a dovetailed joint, it probably has little more strength than a finger joint.

Agree? :wink:

John

 

[János]

Hello,

One must select the joinery used in accordance with the type of load. Dovetails were developed to withstand pulling loads and racking, in an age of unreliable adhesives. Dovetails are joints based on mechanical interlock, and would hold without any adhesive. The adhesive put into a dovetail simply locks the joint, and provides some strength against racking, but has no real effect on the pull strength. Perhaps the actual cross section of pins matters more than the width of individual pins, so a few wide pins would held as well as more numerous narrow ones. On some ancient pieces you can see dovetails fixed with wooden pegs... Widely available reliable animal protein adhesives were a development of the XVIIth century...

Have a nice day,

János

 

[Jacob]

...... Widely available reliable animal protein adhesives were a development of the XVIIth century...

Hmm. Invention of fire about 800000 years ago. Cooking of animals followed. I'd be very surprised if bone and hide glue were not extremely ancient. Resins even older?

 

[yetloh]

Think you are right there, Jacob. It is believed that the Egyptians used animal glues and there is evidence that the Sumerians used it even earlier, so hardly an invention of the 17th C.

Jim

 

[János]

Hello,

Widely available reliable animal protein adhesives were a development of the XVIIth century...

And the accent was on WIDELY AVAILABLE RELIABLE.

Hot hide glue as a reliable commercial product was a development of the XVIIth century in Europe. And this development served as the base of the "veneered furniture revolution"... Before that marquetry and veneering was a rarity on European furniture.

The production of high and consistent quality animal protein glue is a demanding task, even today, in the age of automated processes, and was much more difficult in the past...

Not too hard to find texts about the development and history of hot hide glue in conservation/museology resources....

Have a nice day,

János