Workbench Build #14: Leg Tenons

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Blog entry by Mark Kornell posted 12-08-2014 04:00 AM 2581 reads 0 times favorited 3 comments Add to Favorites Watch
« Part 13: Finishing the Wagon Vise Install Part 14 of Workbench Build series Part 15: Leg Into Top Mortises »

To join the legs to the top, I’m going to use blind tenons. I didn’t quite have enough lumber to do the full through dovetail tenons – my leg blanks are about 1” short! C’est la vie.

I’d glued up the blanks months ago and left them rough. So I start by foursquaring them. Joint two adjoining faces, plane the other two. Kept at the planer until all four legs were surfaced on all sides, resulting in them being 5 11/16” square.

Next step was to trim the ends and get them all the same length. Clamped a small scrap of plywood to my TS fence to act as a stop.

And then trimmed one end of each leg. Took as little as possible off, maybe 1/4”. With the saw blade raised all the way, even after cutting all four sides, there was a small nub left. The flush trim saw and block plane took care of that pretty quickly.

For the second side of each leg, I set the fence/stop at my desired leg length. Then repeated the four cuts/flush trim/plane process on each. That left me with a stack of identically sized legs:

That’s about 140 lbs worth of legs.

Time to lay out the tenons on the legs. For the front legs, the tenons will run with the length of the top. That will ensure the front legs stay coplanar with the front edge of the top. Their mortises need to fit tightly on all four sides to help counter racking forces.

For the back legs, the tenons will run across the top. Their mortises will have additional length to allow the top to expand.

Clear? I don’t have pics as the pencil lines on jatoba don’t show up well on camera.

Now to cut the tenons. Most of the work is done on the table saw, so it went quickly.

First, lay out the tenon depth and set the stop on the xcut sled accordingly. All the tenons will be cut using this stop setting to ensure the leg lengths are all identical.

Then, for each leg, set the shoulder depth according to the layout lines. As much as possible, I made the legs symmetrical so I could use the same stop setting for multiple cut.

Once the shoulders were cut, set up for cutting the cheeks. Set the saw blade height to the tenon depth and leave it there, as all tenons will be cut to this depth.

Then set the stop to cut the outer cheeks. Not like this!

You don’t want to trap the offcut between the stop and the blade, so move the stop to the other side.

Like this:

And cut

Note the clamp. While a leg this size standing on end is relatively stable, it still needs to be supported while moving. Rather than worrying about it tipping – or worse, reaching after it if it starts to fall – just clamp it securely to the sled.

Adjust the stop as necessary and soon there a four legs with tenons. Because of how I laid out the tenons, I only had three stop settings.

Not done yet. I want double tenons on each leg. More surface area for glue.

Lower the blade half a turn, set the stop for the inside cheeks.

Rotate it 180° and make the second cut.

Then waste away the material between the two inner cheeks. Soon you’ve got:

I found out that if you leave a slight sliver of wood between the kerfs, the table saw captures much more of the sawdust. As opposed to spitting it out all over you. The slivers break away easily.

To finish off the inside shoulders, I used my router. I didn’t have a template bit quite long enough so I used my 1/2” downcut bit and will let the shaft of the bit be the pilot.

Get it in the router and set the plunge depth.

Clamp the legs to something stable:

And route away the inside shoulders. I ended up with:

You want to wear some basic PPE. If you’re like me, you crouch down to have a good view of where the router bit is going. And the router chips are going to be flung at your face at high speed.

Mortises into the top are next.

-- Mark Kornell, Kornell Wood Design

3 comments so far

View Mainiac Matt 's profile

Mainiac Matt

8489 posts in 2499 days

#1 posted 12-08-2014 03:00 PM

very crisp and clean looking tennons

-- I yam what I yam and that's all what I yam

View Mauricio's profile


7144 posts in 3322 days

#2 posted 12-08-2014 03:57 PM

Nice Legs!

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

View terryR's profile


7387 posts in 2479 days

#3 posted 12-08-2014 04:17 PM

yes, very clean!
Nice work.

-- tr ...see one, do one, teach one...

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