Double wedged tenon – Advice sought

AlanTurner | Posted in Joinery on January 10, 2003 05:42am

I am building a workbench. From Landis’ book, a modified Fortune Nelson bench. Just about done with the base, and a question arises. The legs, (2.75″ sq.) join the sled foot (3 X 3) via through M&T. There is about 4″ between the leg and the end of the sled base. The tenon is 3″ long, 1″ X 2.25″. Fortune/Nelson/Landis spec. a double wedge here, and I agree. I’m just not sure about the details.

What angle? Would the angle in the mortise be for the full 3″, or perhaps 2″? How far in from the end of the tenon should the cuts for the wedges be? Per Frid’s first book on joinery, he says to drill a “stop” hole at the bottom of the wedge groove to prevent further splitting. Is this a good idea? I know that the way the joint works is mechanical, and since the action of planing on the bench will exert much lateral force, this is a critical set of joints. And, of course, I am out of 12/4 maple, so it needs to be right the first time.

Advice is respectfully sought. Thanks.

Replies

SgianDubh | Jan 16, 2003 06:29am | #1
Make the exit of your mortise about 6-10 mm (1/4"- 3/8") bigger than the entry. It needs to slope evenly almost to the entry of your mortise.

Cut a tenon saw or bandsaw kerf in your tenon about 3/16" in from each edge stopping about 1/2" short of the tenon shoulder. Centre a 5/32" or 3/16" drill bit at the end of the kerf and bore through the tenon.

Cut wedges that are about 2-1/2" long that are at least 3/16"+ wide 1/2" in from the fat end-- you might use an offcut from the tenon-- and nicely tapered. they don't need to come to a pont at the narrow end

Assemble and clamp up the joint, slop some glue on the wedges, and drive them home with a hammer. When dry, cut off the overlength wedge and smooth it all down.

Don't trust my calculations in imperial measure. I'm hopeless at fractions. Slainte.

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Edited 1/15/2003 10:31:53 PM ET by RichardJ

AlanTurner | Jan 17, 2003 01:54am | #2
Richard

Thanks so much for the help. I see you agree with Frid on the hole. And, today I received the Ency. of Furn. Making from Amazon, together with an email from Amazon saying that shipment would be delayed. Curious.

Reading and enlarging mortises, etc., are on tonight's agenda. Can't wait.

Alan