Mortice and Tenon joints

[gold leader]

Hopefully a fundamental question, but I want to get it right......
How deep should a mortice and tenon joint be? Im sure there is a simple rule of thirds or halves that applies, but I can't find it. Thanks in advance

[Wood Borer]

I recall a similar thread probably about 12 months ago. Try doing a search and perhaps all will be revealed.

[jow104]

I think you can safely assume the tenon should be a third (thickness), depth for me depends on what tool I have available.

[derekcohen]

Rule of Thumb is 1/3 the depth/width.

Regards from Perth

Derek

[jacko]

From bitter experience, when deciding on the depth of the tennon, dont forget that if you are rounding the corners (usually done post assembly) that you have clearance with the end of the tennon! I have a pair of small doors with just about 0.5 mm of tennon showing through on all rounded corners and therfore i am remaking the
dddd doors!
Jacko

[Different]

I contend that if strengthis the aim the longer the glueline the better therefore the tennon should be as deep as possible in fact I contend that a through tennon has strength advantages over any stopped tennon Provided a reasonable ammount of material remains before the end of the member.


ross

[AlexS]

Have to agree with Ross. Wedged through tenons will be even stronger and can look good.

[TassieKiwi]

Yeah - what AlexS said. I used wedged babies on my bench. Hurricane Ivan wouldn't budge'em. They do look good, too.

[Marc]

On the topic of tenon size ... (err no pun intended), I agree that a longer tenon will withstand stronger lateral forces. My question is, how thick?
Too thick will weaken the mortised section too thin will make the tenon weak, Is it 1/3 again?

[John Saxton]

A rule of relative dimensions 1/3 is what I work by Marc...held me in good stead so far.

Cheers :)

[Different]

On the topic of tenon size ... (err no pun intended), I agree that a longer tenon will withstand stronger lateral forces. My question is, how thick?
Too thick will weaken the mortised section too thin will make the tenon weak, Is it 1/3 again?
Once again if strength is the main aim then multiple thinner tennons is preferable to one larger one .
ie: if joining a 2" pail to a post of say 75mm then 2 tennons of 10mm width separated by 10mm is far stronger than single 1/3 width tennon of 17mm.
Add up ghe glue surfaces if you dont agree.
Also the height of the tennon in this situation is more important than the width.
That is to say a tennon made to resist racking forces should look very different to one designed to support high static weight.

[lesmeyer]

Hi,
just to add another angle. I see that David Marks often uses loose tenon joinery using the 1/3 rule of thumb. Maybe this will be stronger depending on the wood used for the loose tenon.
Regards
Les