mortise & tenon formula?

[larry merlau]

what is the formula for determining the length and width on mortise and tenons? does the wood specie factor in as well? is glueing just the tenon sufficient or do you still glue the flat surface area as well? thanks for the info, thought it was a good question for us amautures to get info from the WIZE ones.:D

[Keith July]

Hi Larry,
I use the 1/3 formula....The thickness of the tenon is 1\3 the thickness of of the board. i.e. 3/4" material would have a tenon 1/4" thick. The length of the tenon is figured at 1/2 (the width of the board) as a minumin length. However you can make the tenon as long as you like, a through tenon being an example of the longest.
With a small brush I apply the glue to all surfaces of the mortise.

Keith

[tod evans]

larry, i`m far from wise but i agree with keith......02 tod

[Mark Singer]

The 1/3 formula is a good rule of thumb as Keith ststed on width. On the length, the long grain surface should be maximized. Many tenons only need 2 shoulders, unless the boards are joined at the end ofone and the top edge of the other. On wide boards , sometimes 2 tenons , side by side is best...It increases the glue surface. On very wide tenons the joint should be haunched...so twisting is less of an issue.

[larry merlau]

i have a 3/4" thick by 4" wide leg that is going to get a mortise so it should have a mortise of 1/4" thick by 2" wide and 2" deep the stretcher is also a
3/4" x 4"??

[Roy Wall]

i have a 3/4" thick by 4" wide leg that is going to get a mortise so it should have a mortise of 1/4" thick by 2" wide and 2" deep the stretcher is also a
3/4" x 4"??

Larry,

My thoughts are you can get a 3" wide mortise w/ tenon out of that 4" wide stretcher....leaving 1/2" shoulder top and bottom; and 1/4" shoulder on the sides....

Sounds like you're using loose tenons....??

[Calvin Hobbs]

On most of my standard rails, aprons, etc. they are all 3/8" because the mortiser is set up with this standard bit.

There are plenty of ways to get more exact in the dimensions, etc. but practicality and speed win out and 3/8" works well for most applications.

Cal