Retrofit Mortise and Tenon Joints

I once had a large table that would have been great except for weak joints between the apron and table legs, which made the table wobbly.  I wanted to strengthen the table without modifying it, and decided to see if I could retrofit mortise and tenon joints.

After removing the top, I drew in ¼” x 3” rectangles where I planned to add hardwood splines, at all 4 corners of the table.
 First, I drilled ¼” x 2” deep starter holes at one end of the rectangles. Then I used my router, with a ¼” upcutting bit, to rout in several passes ¼” wide by 2” deep grooves along the length of the rectangles. Next, I glued and tapped in ¼” x 3” long x 2” deep hardwood splines.

The final result was a rock solid table, finally with strong joints.

This sketch shows the concept; looking down at the 2x2 leg and the 1x4 aprons that support the top. In dark is the added spline.

Step 1: Mark out location for reinforcement

As you see in this photo, I marked with black felt pen where I will cut a groove with the router. The board held with the C clamp serves as a guide for the router. I have a 1/4" straight cut bit in the router.

Comments

[Balord]

Bill, attach a small cleat on your guide protruding about 1/2 inch form under the guide, this (in your photo example) would give you a nice level surface for the router. If I ever get the ambition to do so, I have a nice coffee table I built which has a system I would have used on the table you tightened up, I'll take a few pics and send them up....all I need to do is loosen a wing nut and I can take the legs off for compact transport! You can actually buy metal cleats to do it as well but my whole table is a custom one off design completely from my head though the top is only 3/16" oak ply I can jump up and down on it!

[Bill WW]

Thanks, Balord -
I actually did this project several years ago, might have been one of my first projects with a router. However, in retrospect, I still believe it is a reasonable way to reinforce a rail-to-leg connection.
Would like to see your photos.
Regards,
Bill

[Greg1109]

Two words... pocket screws.

[Bill WW]

Thanks Greg, you are correct of course. This was the first of this design I had made, and had actually already tried pocket screws which did not work out well. Could have benefitted from a pocket screw jig.
So, went to option #2, which is why I called this "retrofit" mortise and tenon.
Actually did this project about three years ago so by now maybe I could have got it right the first time!

Bill

[LynxSys]

Even if this could have been done with pocket screws and an expensive jig, this method is tons stronger. It's also a good deal stronger than the work that a power biscuit joiner can do. For this application, I think that this was hands-down the best way you could have done it. Solid work!

[trog2000]

Aren't these really biscuit joints? Any nice job and far superior to pocket screws.

[Bill WW]

I guess they could be considered biscuit joints. My friend has a biscuit joint cutter I once borrowed, the biscuits were quite a bit smaller than the oak splines I used for the table.

The rest of the story - This was a project I did several years ago, and had tried pocket screws. They did not work for me, table was wobbly! So I did this "retrofit" to correct my pocket screw failure. Was really not much harder than the pocket screws, but again, I did not have a nice pocket screw jig, like sold by Kreg.

Thanks for the comment.
Bill

[rimar2000]

Thanks for sharing this useful info, Bill.

[Bill WW]

Muchas gracias, Osvaldo!

Bill