[Budprine]

I'm considering making some six panel doors using red oak. I've been checking YouTube for pointers and one guy indicated he was extending a tendon into a deep mortice to increase the strength at the stile. Is this normal? I only saw this one place.

 

[jagans]

Tenon, not Tendon

Generally the size of the mortise and tenon is related to the thickness of the timbers. It is considered good practice to proportion the tenon as one third the thickness of the rail, or as close to this as is practical. The haunch, the cut-away part of a sash corner joint that prevents the tenon coming loose, is one third the length of the tenon and one sixth of the width of the tenon in its depth. The remaining two-thirds of the rail, the tenon shoulders, help to counteract lateral forces that might tweak the tenon from the mortise, contributing to its strength. These also serve to hide imperfections in the opening of the mortise.

 

[Bruntson]

Yes it is normal to use motise and tendon joints for six panel doors for the strength needed at the corners.

 

[jagans]

Tenon, Not Tendon!

Mortise and Tenon