need to replace broken tenon from chair joint

[Don Morris]

I have an outdoor chair...not sure of the type of wood. My guess is cypress. One arm was secured to the piece below it with mortise and tenon joinery. That broke with loss of a a good portion of the tenon. I think the tenon was undersized. My thought is to rout out both sides and use a floating hardwood tenon, a little larger and perhaps a tad longer. My difficulty in the past with doing such a technique has been to accurately mark both sides so the mortises line up. I seem to have difficulty with the system I used, thus this plea to the experts on how to accomplish that with good accuracy. Any advice here will be greatly appreciated. Thanks in advance. Don M

[Jim Dwight]

If you have some dowel centers you could bore holes in both pieces for the ends of the mortises using the dowel centers to transfer the holes from one piece to the other. The holes are handy for cutting mortises with routers because it can be difficult to plunge the bit into the wood.

[Ken Krawford]

I've done a version of what Jim suggested with one modification. I drill one end of the repair using a drill bit sized correctly for the dowel. I glue it up and let it cure. I drill the mating hole on the other piece larger than the dowel diameter and use epoxy to fill the joint and any void around the dowel. This allows you some "wiggle room" in aligning the two mating pieces for a perfect fit/alignment.

[John Kananis]

If you're trying to mark by measuring, forget it - too much margin of error. Use a making gauge for the parallel lines. For the perpendicular, mark the face of the two parts to be joined and transfer to the cut area with a square. Knife marks are more accurate than pencil.

[Prashun Patel]

Does the tenon need to be hidden? Can you just drill through the arm into the post and secure with a dowel?

That one arm may appear different from the others. But nobody will really notice imho.

[Doug Garson]

Another way to mark matching points on the two pieces is to hammer a finishing nail into one side, cut it off with wire cutters about 1/16" long, line up the two pieces and push them together marking the matching location on the second piece, pull out the nail and you have matching points to drill for dowel. Ken's idea using one oversized hole and thickened epoxy is a good one.

[James Jayko]

There is a good article in FWW about Philip Morley's floating tenon jig (Jan / Feb 2023 issue). All you need is a way to find center on the parts and line up the jig with the center lines. I've used it on a few projects and it works shockingly well given the simplicity of the design.

[Don Morris]

thanks guys for the assist in aligning up mortises for the floating tenon. I think I like the idea of gluing one end of the tenon in with regular titebond and drilling out the other side a little larger filling the gap with epoxy. I'm going to look now for the article recommended.The finishing nail trick sounds like I ought to try a sample dowel placement using the nail technique. That might force me to change my mind on the procedure of choice.. The tenon should be hidden although I agree with some careful finishing a direct dowel replacing the tenon is a possibility. Thanks again, I'm off to do areticle research. Don M