Chair back rest

[Colarris]

Just working on my first ever chair and I have to say I've forgotten a fair few points from my wood working lesson a few years back.
Im working on the uprights of the back rest back and just cut my first tenon but Im just wondering if the tenons are too long? I remember my teacher telling me they have to be about 2/3's of the width of the wood it was being slotted in to but the tenon is quite thin, just over 5mm, and Im wondering whether it might snap. Should I cut it shorter so it will be stronger? I can post images if that helps?

 

[OPJ]

A photo or some form of illustration would definitely help. You're probably right with the two-thirds ruling - unless, perhaps, your rails are 100mm wide or something?!? :wink: Generally speaking, you would also aim to make your tenon thickness equal to one-third of the rail thickness; depending on the closest chisel size available. So, 5mm may be about right, depending on the thickness of your timber.

 

[Colarris]

Thanks for the reply, here's the images.

Do they necessarily have to be that long and/or is the width and length an issue? [/img]

 

[OPJ]

Thickness looks fine so, I don't think it's likely to snap under load.

You could trim a few millimetres off the width (both sides) so that if the accidentally over cut the mortise or the timber shrinks slightly, the mortise cannot be seen. :wink:

Length-wise, I think 20mm would be fine, or 25mm at most, as it's only a stub tenon (ie. not going all the way through the rail).

 

[Colarris]

Thickness looks fine so, I don't think it's likely to snap under load.

You could trim a few millimetres off the width (both sides) so that if the accidentally over cut the mortise or the timber shrinks slightly, the mortise cannot be seen. :wink.

Thanks for the info, yeah I was planning that, I've messed up enough joints before realizing I could hide my mistakes that way!

Thanks for resizing my images for me, whoever it was.