angled tenon or angled mortice?

[cerdeira]

I'm planning to build some chairs based on a traditional design ie with a front rail (the one under the seat) longer than the back one. That calls for angled tenon joints: they're much easier to make by hand than chopping an angled mortice and dealing with angled tenon shoulders.

Yet, I've recently stumbled upon an article online (can't remember where) describing the construction of a period chair where angled mortices were used because that was the traditional way.

Why did ancient craftsmen do that? Can't think of any advantage unless the angle is so small that an angled tenon would degenerate in almost end grain, which isn't the case of a chair.

Am i missing something?

 

[jasonB]

If the angle of the tennon is too steep you can get short grain - tennon likely to snap as the grain runs accross it rather than along it, thats the only reason I can think of.

Jason

 

[Larry James]

I'm planning to build some chairs based on a traditional design ie with a front rail (the one under the seat) longer than the back one. That calls for angled tenon joints: they're much easier to make by hand than chopping an angled mortice and dealing with angled tenon shoulders.

I can't post a picture, however, visit Project Gutenberg EBooks at: gutenberg.org.

Search for this book: EBook #21531, The Project Gutenberg EBook of Woodwork Joints, by William Fairham. Look at Fig. 173.—Tenoning Narrow Rail. You will need to view the HTML version to see figures.

By chance, I happened to be looking at M&T joints in this ebook yesterday. I'm sure you will find this book very interesting. Not ancient, but early last century.

Trivia:
PRINTED IN GREAT BRITAIN BY THE WHITEFRIARS PRESS, LTD.,LONDON AND TONBRIDGE.
THE WOODWORKER SERIES
WOODWORK JOINTS: HOW MADE AND WHERE USED (Revised Edition). With 400 Illustrations and Index. 3/6 net.

Larry

 

[cerdeira]

I think i've got it.

The joint between the seat side rails and the back legs is the most stressed one in a chair.
Angled mortices will prevent the joint to come loose acting somewhat like a dovetail.
One can figure this out by mentally assembling the chair: the sides must be assembled before the front and back rails and crest, otherwise it would be impossible to drive the tenons in the side rails into the back leg mortices.
Those guys from ancient times were smart.

 

[Larry James]

I think i've got it. ...
...Those guys from ancient times were smart.

Sounds logical.

We stand on the shoulders of the ancients. We find the answers using the internet, books, magazines, etc. Imagine the ancient woodworker - he used trial and error, genius, hard labor, and necessity to do what we take for granted. I'm awed by what they accomplished.

Larry