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The stand-up desk – joinery for the front apron

September 1, 2009 By

A few days ago I showed how I made the drawer fronts and the front apron for a stand-up desk I am building:

layout-front-apron-drawer-fronts-2

Now it is time to make the mortise & tenon (M&T) joinery that will hold the front apron on the legs.

I did something to my left shoulder while lifting a replacement riding mower engine; as a result, pain is keeping me from lifting my left arm above chest height at this time – but it has improved quite a bit. I was thus unable to use the Leigh FMT to make mortise & tenon joints – I hate not being able to use my favorite joinery machine. This meant Plan B had to be implemented.

Plan B: Mortises on the Delta mortising machine (easy decision). Then I had to decide how to make the tenons; I had two three options:

1) The table saw, using a) the tenoning jig, or b) a stacked dado; or, as an alternative,

2) The band saw. Even with a wide blade, making a 6-inch long tenon on the band saw is probably not the best option for critical joinery like M&T. I discarded this option.

Edit to add (after a suggestion by Kari, aka The Village Carpenter, on Facebook):

3) A hand saw. I discarded this option right away, as I truly am not that good with a hand saw…yet. Plus, I don’t have a good tenon saw – maybe it will make a good Christmas gift, don’t you think?

I selected the table saw, using the Delta Deluxe tenoning jig. But first I had to make sure the 67-inch long apron would not hit the ceiling – it fit, with plenty to spare:

tenons-front-apron-ts

The drawer openings in the apron are obvious in the photo above. To provide adequate bracing while in the tenoning jig, the apron had to be supported with another piece on the clamp side – in the photo below I am making a test cut on a waste piece, sizing the tenon thickness, and including the outboard support:

apron-tenoning-jig

I used a sacrificial board on the back side of the tenoning jig, to minimize the risk of blowout on one of the edges of the apron – the tenoning jig includes the black plate just for this purpose:

apron-tenon-hig-backup-support

Finally, to reveal the tenons, I cut the shoulders using the cross-cut sled:

tenons-cutting-shoulders

The full tenon is now done: In the photo belowI have just used a chisel to slightly undercut the base of the tenon. This will ensure I can completely drive and seat the tenons in the mortises – a neat trick to remember:

full-tenon-front-apron

Next I will split each tenon into two. After that, all that remains will be a little clean-up of the tenon cheeks, to custom-fit each tenon to their corresponding mortise. Oh, how I miss using my beloved FMT!

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Filed Under: Blog, FMT Pro, Joinery, Mortise, Tenon Tagged With: , , ,

The Leigh FMT: When absolute precision is a must

August 20, 2009 By

I am in the process of building a stand-up desk. The design includes a full dust cover, which doubles as the support structure for four drawers. For the construction of the dust cover I selected 6-inch wide boards, to minimize flex of the structure under the load of the drawers and of the ribs required to keep the top from cupping (I will include all the desk design details in a future entry).

The photo sequence that follows illustrates the precision and accuracy delivered by the Leigh FMT. I decided to use double tenons along the width of the short boards in the frame, to minimize the risk of wood movement across the grain, causing cracking in the boards with the mortises. To obtain perfect alignment, the FMT allows very precise positioning of the center of each tenon and mortise. Thus, the FMT was my choice.

In this first photo I am cutting the first of two tenons:

cutting-first-set-tenons

By sliding the table on the FMT to allow centering on the second tenon, I can confidently cut that tenon:

cutting-second-set-tenons

Following some test cuts on scrap pieces, I confidently cut the mortises on the long mortise boards:

double-mortises-2

A different perspective, showing the double mortises more clearly:

double-mortises

The following photo shows the components of the dust cover frame; the slots in the tenon pieces and on the mortise boards will accept the ¼-inch boards that will complete the cover:

tenons-and-mortises

The photo below shows the first dry fit of the dust cover:

dust-cover-dry-fit

And, finally, the completed dust cover:

dust-cover-after-drawboring

Alignment of the stiles (the tenon boards) was perfect on each of the rails (the mortise boards). Pretty cool!

A key to successful, repeatable results, is the clamp-on Ott table light that Sandy gave me a few weeks ago. It helps my aging eyes to perfectly align the target on the FMT to the center mark locations for the tenons and the mortises. This is what this lamp looks like – but my copy of the lamp has an arm that doubles the reach of the arm, making it very handy for use on the workbench:

I simply clamped the light to a board, and used two additional clamps to install the light on one end of the 3-1/2 inch thick workbench top. My eyes thank me for doing this. Thank-you, Sandy! True love in the shop.

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Filed Under: Blog, Education, FMT Pro, Joinery, Leigh jig, Mortise, Sponsor, Tenon, Tutorial Tagged With: , , , , , , ,

The case for drawboring: Easy, and simple

March 27, 2009 By

Clamping large objects can test one’s contortion prowess, and can often result in less-than-perfect looking mortise & tenon joints due to unsightly gaps. I tried the drawboring technique for the first time on a new base for a (new) 60-inch long table; these usually require long clamps, and maybe a second human’s help to properly position the clamps to draw the joints tight.

I found one article (Drawboring Resurrected, Woodworking Magazine, by Christopher Schwarz, September 1, 2005)  particularly helpful as I prepared to assemble the table base using the drawboring technique. I will show my results, and leave it to the reader to read the how-to in the article by Schwarz.

I used no clamps to get the following, perfectly-tight mortise & tenon results:

Drawboring: The results

Pretty cool! I was able to do this in a fraction of the time it took me the last time I made another table base. And I was also able to eliminate most of the stress of assembling the 3-inch tenons in their mortises, by simply making the fit a little sloppy by 0.005″ (an additional five thousands of an inch), on the Leigh FMT.

Before starting on the actual table base, I did a little test as follows. I simply sliced a test joint, assembled without glue, to allow me to fully dissect it:

Drawboring: Detail 1

The photo above needs some interpretation: The tenon was inserted from the far end, toward the reader. I drilled a hole through the mortise to accept the ¼ peg; I also drilled a hole in the tenon, offset from the hole in the mortise by 1/32-inch, away from the reader.  The bend in the ¼-inch peg suggests that the place where I drilled the offset hole in the tenon was slightly off-center, relative to the hole I originally drilled through the mortise.  But this exercise confirmed that the taper I made on the tip of the peg was good enough to allow it to fully seat.

Exploring further, I removed the tenon piece from the mortise, to learn if additional details would support my conclusions above. Remember: I used no glue in this test piece.

This is what I saw:

Drawboring: More detail

The tearout  on the left side of the hole confirms (I think…) that I drilled the hole in the tenon slightly off-center. And yet the joint was pulled together perfectly tight!

I am sold on drawboring as a technique to help me get nice, tight mortise & tenon joints without using any clamps at all. And I did not have to buy any drawbore pins, as we already had some in our tool box – but we thought they were just “center punches”.

Does anyone think I could make a killing by selling the clamp extenders I bought for my Bessey clamps?

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The Leigh FMT:

Filed Under: Blog, Joinery, Mortise, Tenon

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