m/t's again

[engineerone]

in my other thread, jacob mentioned that i was wrong in the dimensions of the tenons on my table so.

the question is this, you are normally told to make the m/t's 1/3 the width. but the width of what???

jacob said the width of the mortice piece, where as i made the tenons 1/3rd the size of the apron, not the legs.

so am i wrong, is jacob right, or is there another way??

paul

[mailee]

I have always assumed that it means the width of the piece of timber the mortice is in IMHO.

[jfc]

I'll agree with that .

[engineerone]

oh well another f*** up ;D

but since it doesn't say anywhere where did you learn this???

thing is this could i guess mean that sometimes the tenon is the width of the piece itself? or should they all have shoulders??

paul

[andy]

I would say 1/3 of the apron/rail ie the tenon as this is generally the thinner piece

But Jacob was referring to a design constraint where the rules have to be modified to suit

[Alf]

Instead of getting caught up on the 1/3 thing, just remember the joint's only as strong as the strongest section. So f'rinstance it's no good having a thicker tenon if the walls of your mortise are in danger of blowing out.

Dunno if you get Woodworking magazine at all, Paul? Chris Schwarz did a nice article on M&Ts that considers these things back in, iirc, the Spring 2007 issue. S'probably in the bound edition if you have that. (Just checked - it is)

Cheers, Alf

[engineerone]

thanks again alf, in this instance it is certainly not the mortices that will blow ;D i must consider that in a different size of item then the tenons might cause a problem, but as long as they last for about 5 years then who am i to complain

will check which last woodwork i have, think i have that will check again.

so far in recent months have only cut 40 or so m/t's by hand so am obviously not as practiced as many. the important thing though is that when you reduce section sizes you need to look more carefully at the whole situation

paul

[mrgrimsdale]

It's 1/3 MAX for the width of mortice, so e.g. a 30mm stile or table leg would suit a 10mm wide mortice. But it's not an absolute rule, so 12mm would pass in this instance.
The rules for the tenon are: that it should fit the mortice , and be 1/3 MIN width of the apron/rail or whatever. So it can be full width of rail (if it fits the mortice) i.e. no tenon at all, but housed in the stile/leg. Shoulders are helpful however for accuracy and structural stability.

cheers
Jacob

[mrgrimsdale]

mrgrimsdale said:

It's 1/3 MAX for the width of mortice, so e.g. a 30mm stile or table leg would suit a 10mm wide mortice. But it's not an absolute rule, so 12mm would pass in this instance.
The rules for the tenon are: that it should fit the mortice , and be 1/3 MIN width of the apron/rail or whatever. So it can be full width of rail (if it fits the mortice) i.e. no tenon at all, but housed in the stile/leg. Shoulders are helpful however for accuracy and structural stability.

cheers
Jacob

PS But inspite of this vague general rule, most ordinary joinery is made to finished sizes of about 44mm (external doors, windows) to 36mm (internal doors) and a half inch M&T is used almost everywhere.

[mel]

not again paul

in my case it depends on the size of my sharpest hollow chisel morticer ;D ;D

[engineerone]

thank you mel for bringing the levity back to things ;D

i tend to work with the wood itself, and by hand cut them so to an extent, i am stuck with either 4mm, 6mm or up

mind you next time i make an anorexic table i will almost certainly use the rat to help.

paul

[mrgrimsdale]

Paul, I just spotted your shaker table design as a project in the free downloadable sample of Woodworking mag; www.woodworking-magazine.com/
Might be worth a look if you are still at it.


cheers
Jacob

[engineerone]

thanks jacob i had seen that design, in hard copy.

mine is indeed a modified version to take advantage of the
space it will need to live in.

paul