Tapered Mortise-and-Tenon Joinery for a Snug Fit

I’m ready to carve the seat for my chair – one of the parts of the build that I’ve been looking forward to the most – but first, I need to get the legs fitted up. I start by reaming the holes to a 6° taper, using the tapered reamer that I built a few weeks ago. The tapered mortise make a stronger joint than a cylindrical mortise, plus it makes the chair easier to to assemble, so it’s the perfect joint for the leg-to-seat connection. I clamped the seat to my shavehorse so I could work on it at a comfortable height and give room for the reamer to poke through.

Reaming (2)

I set my bevel gauge to the desired angle, minus 3°. Since the angle of the reamer is 6°, cutting that number in half and sighting with the bevel gauge will result in the appropriate angle. Sight the angle every few turns. Once I have it nailed, I can keep reaming until the hole is tapered all the way through.

When the mortises are reamed, I can set my sight on the matching tenons:

Tapering (2)
I use a pair of calipers and a parting tool to get the tip down to 5/8″.
Tapering (3)
Starting off, the tenon is too big and not tapered.
Tapering (4)
I turn it down to the correct taper, but it’s still too big.
Tapering (5)
Now it’s getting close. Time for a test-fit.
Reaming
On the first try, it looks good from above. But not poking through all the way below. Back to the lathe. On the second try, the fit is just right. Three more to go.
Reaming (12)
And there it is. Four legs fitting snugly into their mortises. Now the carving can begin!
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