Mortise and Tenons -

JPG · Post by **JPG** » Sun Jul 03, 2011 9:56 pm

dcottrill wrote:Thank you for the excellent discussion. It looks like a split.

The angle is for design, and it maybe off in the diagram as I'm still working on the exact angle (approximately 67 degrees). It is inspired by Scandinavian designs. They tend to have a different bend to children's furniture.

The seat will be stationary and the foot rest will adjust up or down depending on the child's height.

The pinning of Mortise and tenon joint is an excellent idea, one that I've been considering.

I thought that the forces on the joint would tend to cause a downward motion on the leg resulting in a "clock wise" twisting motion at the joint.

Hopefully, the child is under 100 pounds. It maybe prudent to design for an occasional use by Dad or Mom!

Not discussed is whether it would be better to reverse the mortise and tenon on the two pieces. I would still favor the lower version. I would extend the back end of the 'foot' past the back of the leg to provide more material behind the mortise. The back edge of the leg tenon would have the 'hook' detail.

michaeltoc · Post by **michaeltoc** » Mon Jul 04, 2011 7:03 am

JPG40504 wrote:The 'problem' with the angled joint is that the load results in torque being applied.

You are so right! I was just looking at the floor reaction, totally ignoring that a point load is applied at the opposite end of the leg - which results in a torque.

dusty · Post by **dusty** » Mon Jul 04, 2011 8:54 am

This simple wood working project is starting to sound like a grossly over engineered Government project.

Stress, torque whatever; do a good glue joint and it will hold.

Some of you may find this to be interesting reading.

JPG · Post by **JPG** » Mon Jul 04, 2011 12:33 pm

dusty wrote:This simple wood working project is starting to sound like a grossly over engineered Government project.

Stress, torque whatever]this[/URL] to be interesting reading.

Yes it was! Surprised that the m/t was not much better than the doweled.

Did not say much about angled m/t joints.

Interesting grain orientation observation!

Thanks!

dcottrill · Post by **dcottrill** » Tue Jul 05, 2011 10:48 pm

Originally Posted by dusty
This simple wood working project is starting to sound like a grossly over engineered Government project.

Stress, torque whatever; do a good glue joint and it will hold.

Some of you may find this to be interesting reading.

Very interesting review. I like the mortise and tenon for this joint. My pieces are 1-1/4" thick, not 3/4". The test run with the 3/4" boards 4" wide seems very idea for the dowel joints. Narrow it down to 3" or 2-1/" and the dowels may not offer the as much strength.

A good glue joint seems to be key in all the joints that were tested.

I'm leaning towards the bottom joint and pinning it.