Designing, Laying out, and Cutting Double Tenons to Attach the Workbench Top – Part 2

This post is a follow on to Part 1 that I posted yesterday.

With the baseline or shoulders of the tenons laid out and knifed in, I needed to determine the arrangement of the two tenons on the top of the leg.  I set my first wheel marking gauge to exactly match the thickness of the sapele edge board on the benchtop. This much of the leg has to be removed to avoid cutting into the sapele.  I then had to figure out how to divide up the remaining portion of the leg into two tenons.   Time for a quick sketch.

A rough sketch that I made to help me design the double tenons.

I rarely, if ever, draw out full plans for a project, but when I’m planning/designing individual parts of a project, I almost always pull out the paper and pencil.  Somehow, I just need to see the spacing in front of me to decide upon a path forward.

I ended up with two tenons that are about 1 ½” thick, and a very small shoulder at the back.  The space between the tenons is about 1″.  I want to keep a shoulder on all four sides of the tenons, as the full weight of the benchtop will sit upon the tenon shoulders.

Using two wheel marking gauges, I laid out the first tenon.

With these gauges, I laid out the front and back lines of the first tenon and then darkened them with a pencil.

I also marked the lines down the sides.

Using a tenon saw, I cut to the lines, sawing diagonally from each side before taking out the hump in the middle.

Saw at a diagonal until you reach the baseline.

My saw doesn’t have enough depth of plate to go all the way to the bottom of these 5 inch tenons, so I had to finish the cut with my Japanese pull saw.

Cut to the line, paying attention to which side is waste.

I did OK, but I’m not great at this yet.  I was very careful to make sure that I stayed on the waste side of the lines, but I think that I did this a little too well.  I’m going to have some material to pare away with the chisel to get these tenons to fit right.  You can see where I left the line in the image below.

The first tenon cut.

I repeated these two cuts on all four legs before starting on the second tenons.  Before I made any changes to the settings on the wheel marking gauges, I marked these same lines on both the top side and the underside of the workbench top.  I forgot to take any pictures of this step.

New settings on the wheel marking gauges to lay out the second tenon.

I used the sketch that I drew to set the marking gauges to the 3rd and 4th lines, always referencing off the front face of the leg.

This will leave a very small shoulder at the back.

I again darkened the lines with a pencil to make them easier to see.

The second tenon laid out.

I cut these lines the same as before.  I repeated the layout and cut on all four legs.

The second tenon cut.

Next, I used a fine crosscut backsaw to remove the waste at the front and back of the legs. The deep knife-wall that I established at the start of the layout made it very easy to get a super accurate cut.

A fine crosscut saw in the knife wall to remove the waste.

That part was easy, removing the waste in between the tenons is a little trickier.  On the first leg, I attempted to remove this waste with a mortise chisel.  Wow… that was a mistake.  Loads and loads of hammering away with a mallet and a pig sticker chisel.  Lots of energy spent for little and slow reward.

I first tried to remove the waste in the center with a mortise chisel.

You have to go in nearly 3 inches from each side to connect.

This was way too much work and way too slow.

After the first attempt, I decided to bore out the waste with a brace and bit.  Have I mentioned previously how much I love this Yankee 2101A brace?  It really is a thing of wonder and a superbly made tool.  I used a bit that was just slightly less that the width of the waste (15/16″).

On the next leg I tried using the brace and bit to remove the waste.

I bored halfway in from each side to minimize the chance of the bit wandering off the intended course and cutting into the tenons.

A sharp tap with the hammer and the waste falls out.

I hit the waste piece with a hammer to break the last few remaining wood fibers and the piece fell out.  I then used a 1 inch chisel to chop out the last of the waste in between the tenons.  This process was way faster than trying to chisel the whole thing.

With the waste removed, this is left.

I had to do a fair bit of paring to make sure that the tenons were no thicker than the layout lines.  While doing this, I remembered a tool that I purchased in a garage sale some time ago.  At the time I bought it, I wasn’t sure what I would ever use it for, or for that matter what it even really was, but it was in perfect condition and I think I only paid a dollar for it.  It looks to me like a giant float and my online research seems to confirm that.  It’s quite thick and heavy, and about 14 inches long.  I put a file handle on it to make it easier to use.  It does a fantastic job of smoothing out the tenon cheeks.

This large float helped to refine and even out the tenon cheeks.

I removed the waste on all four legs.

Double tenons cut on all four legs.

I took a close look at all of the tenons when arranged together, and realized that I needed to fine tune them a little so that they were more consistent.  I did a little more work with the chisel and float.

They still need a little fine tuning.

To create the shoulder on the sides of the tenons I decided to use the table saw.  I could have gang cut the two tenons with a handsaw, but I felt that this would be easier.  I just want to remove ¼ inch from each side.

I used a stacked dado head in my tablesaw to take 1/4 inch off each side of the tenons.

I went very slowly and didn’t get any spelching or split out.

With the tenons finished, I used a sharp chisel to pare the shoulders slightly and undercut them, making sure that I didn’t change the knife line created in the first step. This should ensure a nice tight fit between the legs and the benchtop.  I also flipped the legs upside down and chamfered the bottoms.  This should stop the edge of the legs splitting out if I ever have to drag the bench on the workshop floor.

I added a chamfer to the bottom of the legs with a sharp block plane.

While on the topic of chamfers, I decided to cut stopped chamfers on the legs and stretchers.  This will break any sharp edges and also serve to dress up the bench a little further.  Life’s not all about practical functionality after all.

I have had a Black & Decker Firestorm plunge router for about 8 years.  It’s an OK tool but it is top-heavy and not ideal for what I want to do.  Something lighter was called for. I’ve had my eye on a Ridgid palm/trim router for some time and figured that now was a good time to pick one up.  I have always been happy with my Ridgid tools and you can’t beat their lifetime warranty.

I mounted a chamfer bit in the router and made a couple of test cuts at different depths to see how heavy of a chamfer I wanted.  I went for the deeper of the two.

I cut a couple of test chamfers onto a scrap of Douglas Fir.

I laid out pencil marks on all the edges that I want stopped chamfers on.  I stopped the chamfers 2½ inches from the top, bottom, and any intersections.  I thought about adding carved lambs tongues by hand to the stopped chamfers until I added up how many that would be.  48 – It’s not happening.

I cut stopped chamfers on all four edges of the legs.

The Ridgid router was a joy to use.  I know that I have been concentrating on handtools lately, but this router really made me smile.  It does exactly what it is supposed to and nothing else.  There was no burning, digging in, or tipping.  It was light and very easy to control.  I’m very happy with it.  The only negative… It made a huge mess, there was dust everywhere.  I suppose that this goes for all routers though if they’re not used with a dust collection system.

I cut the chamfers on all four legs and then gave them a light sanding to remove the fluff left at the end of the stopped cut.  I was careful not to round over any of my nice crisp chamfers.

After a light sanding to remove any fluff left behind by the router.

I also routed a chamfer on the top and bottom of all four stretchers.

I also cut stopped chamfers on the top and bottom of the stretchers.

Well… that’s the legs and stretchers done.  Now I have to put them all together.  I’ll admit I’m a little nervous about hammering those drawbore pegs in.  I’ve done so much work in making these legs, that I’ll be really displeased if they split when I assemble them.  Keep your fingers crossed.

More soon.

– Jonathan White