Tenon joint into curved surface

[Tetsuaiga]

Im looking for a bit of advice with this. Unfortunately I don't think I can alter the design to avoid it.

I presume it's okay to simply shape the tendon and cavity to the shape of the curve. Will this work?

To try and give some clarity what I have is a two slightly wavy pillars which will need a beam inserting between them roughly 3/4 of the way up the pillars. The beam will have to support some weight.

 

[Tetsuaiga]

Ah I should say the curve is horizontal in magnitude. Can't think of a better way to describe it.. more or less an S shape but much less severe.

 

[Benchwayze]

Welcome to the forum Tetsu.

A picture would help, but if I had to tenon a rail into an S shaped stile, I would cut the mortice and tenon straight, and form the shoulders of the tenon to suit the curved stile. So, you'd have to allow for that when setting out.

HTH

 

[Jacob]

Tenon needs to be straight grained and parallel sided but everything else can follow the design.

 

[Tetsuaiga]

Thanks.

Benchwayze - So you would use the depth you wanted on the bottom but alter the top depth to fit.

.........\
..........\
\..........\_______________________________
.\.....____\
..\...|
....\.|______
.....\...........\____________________________
.......\..........\
........\...........\

Hope the piocture helps a bit. The .... are meant to be empty space.

 

[Benchwayze]

Thanks.

Benchwayze - So you would use the depth you wanted on the bottom but alter the top depth to fit.

.........\
..........\
\..........\_______________________________
.\.....___\
..\...|
....\.|______
.....\...........\____________________________
.......\..........\
........\...........\

Hope the picture helps a bit. The .... are meant to be empty space.

Tetsu,

How are you morticing, By hand or machine?

 

[Tetsuaiga]

Most likely hand, though I might start it with a drill.

 

[Benchwayze]

Tetsu,

PM sent.

 

[Benchwayze]

Tetsu,

I'm still not exactly sure what you are making.

But to cut the joint you showed, you either have to angle the mortice, so you can have a straight tenon with angled shoulders. (as you are showing in the sketch).
or;

You work the mortice at 90 degrees to the stile, which means you'd have to cut an angled tenon. Not so desirable because of short grain problems.

Hope that makes sense.

 

[AndyT]

Here's an example of a mortice and tenon at an angle:

This is the bit with the tenon on - you can see that the short-grain corner has been cut off. This also eliminates the need to do any undercutting on the mortice, which is difficult to do and not strong:

 

[Benchwayze]

Dual-purpose item Andy?
Chair and steps?
This is the one you got from the old 'Woodworker' Magazine.. Right?

 

[AndyT]

Dual-purpose item Andy?
Chair and steps?
This is the one you got from the old 'Woodworker' Magazine.. Right?

Yes, and there will be some more progress and an update soon - the pile of bits makes me feel guilty every time I go in the workshop!
But the bench is full of a very dull bit of diy at the moment - re-gluing the joints in a (commercially made) bed.

 

[Tetsuaiga]

Thanks for the updates. I think i've found a way I could simply place the whole beam into the pillars as it can be slightly smaller without effecting any of the functionality I need. I presume that would be just as strong.