I like the look and strength of a wedged mortice and tenon, but just read an article that got me thinking. It recommended drilling a small hole at the bottom of the kerf in the tenon to help prevent splitting it when the wedge gets driven in.
It seems to make sense, but I’ve never seen Mr. Sellers talk about that. Is it a necessary practice?
I saw that article – an extract, I believe from a new book.
It certainly makes sense on the face of it, after all, you are intentionally bending part of the tenon along the grain to insert a wedge and lock the joint.
However, if the neck of the tenon (next to the shoulder) is a tight fit in the throat of the mortise it stands to reason that it cannot split beyond that point…….
If we re-examine the method, the intention is to provide a saw-cut for the wedge and to allow the fibres of the grain down-stream to bend, rather than crack; if a hole aids this, then it’s perfectly valid.
Personally, I’ve never drilled holes in a tenon for that purpose and never had an uncontrolled split, but it ultimately depends on your working practice and the strength of the stock below the joint.
I don’t know what Paul Sellers would advocate…. you’ll have to ask him!
I’m using wedged thru tenons on a chair I’m currently working on. I was told it was very important to get a good snug fit on the shoulder side of the tenon, opposite where the wedges are inserted. A loose fit means any split that occurs from driving in the wedge may just continue along the tenoned piece. Hope this helps and good luck!
Could it be that the holes drilled at the bottom of the saw kerfs are more relevant to fox joints? One only gets one chance on those joints, so it must be tempting to make the mortices a bit wide to ensure that the shoulders of the tenoned part really close up with the mortised part of the joint, with the wedges made wide to assure an “inside joint” tight fit. As that approach seems bound to increase the risk of splitting the tenoned piece, the drilled holes appear more relevant than for a through wedged joint.