Green & Green Settee Part XIV

Center Splat:

The center splat is nothing spectacular to look at.  It will be hidden by upholstery.  However, it will be visible from the back so I want the joinery looking nice.  The splat will have integral tenons and they will be flush with the front (which means there will be no front shoulder, only a back shoulder - this makes things a bit easier).

I had cut the mortise in the back rail long ago before glue up.  I need to cut the mortise in the freshly fitted crest rail.  First, I'll go ahead and remove part of the rabbet with a handsaw and shoulder plane.  While the mortises will be "centered" on both the crest rail and the back rail, it is pretty difficult to get perfect alignment.  Consequently, I'll put side shoulders on the bottom tenon and cut the tenon a bit narrow so I can adjust it side to side.  I will not be able to do that up top with the rabbet.

 

Ok, its time for the tenons.  One can take one of two approaches.  1)  treat one of the tenons as a straight tenon and the other as an angled tenon 2)  treat both as angled tenons.  Now, the former sounds like it would be easier, and perhaps it is a tad easier.  For example, one could treat the bottom tenon as a straight tenon and only angle the top.  But there is a big disadvantage.  Since the entire splat curves back quite a bit one would need a very thick board to make this work.  Also, the top tenon would end up compensating for all of the angle and we will probably end up with a weak tenon.

Option 2 is much more forgiving on the amount of wood required since we can angle the board.  Also, both tenons are angled but the amount of angle on each is not too bad.

First, I establish the relationship between the two tenons.  I put temporary floating tenons in each mortise and glue a piece of plywood to both:

 

The splat front will pretty much have the same shape as the rear posts.  So I use my rear post template to layout the shape.  Then I place the splat jig onto that layout to determine where the tenons will go.

In the photo above note that I have marked where the shoulder will be.

Ok, now I need to cut the tenons.  First, I need to know my angles.  I've learned long ago that if one wants to build chairs then one needs at least 2 bevel gauges - top/bottom, left/right, etc .  Starrett bevel gauges are excellent and well worth the few extra bucks.

I'll use my tablesaw to cut the tenons.  I have a high tech tenon jig (the Mach 7 Tenon Jig) with a perfect 90 degree face to which I will clamp the splat.  Given this fact,  I clamp my splat to a 90 degree surface.  I could use the Mach 7 Tenon Jig but I find it easier to clamp to my jointer fence, which is also 90 degrees (note that the splat has been milled flat and square).  Note that the splat jig is clamped to the workpiece.  After getting the angle for the first tenon, I carefully flip the workpiece and use the other bevel gauge to measure the opposite tenon, making sure that the splat jig stays firmly clamped and does not move.

 

 

Then I clamp it to the Mach 7 Tenon Jig:

Now, given a right tilt blade, there is a risk that the blade could ruin my Mach 7 Tenon Jig.  Fortunately, I have enough wood in front so that this does not happen.  In the photo above, I have cut the front face of the tenon.  I move my fence to the right and cut the back part of the tenon.  My table saw fence has a micro-adjust on it - which makes it easy to dial in for a nice fit.  Still, I leave it a hair thick and finalize the fit with a shoulder plane.  Note that the rear shoulder was rough cut with a bandsaw to allow me to test fit the tenon.

Once the tenon is fitted, with the same blade angle I cut the rear shoulder.

I go through the same process for the opposite tenon, using my other bevel gauge to set the saw blade.  I then cut and fit the other tenon.  Note that I am a bit conservative when cutting the shoulder.  I do not want to remove too much so that there is a gap between the shoulder and the crest rail.  So cutting the top shoulder may require creeping up to the final fit and a pass or two with a shoulder plane.

I bandsaw the front profile and here is the splat in its rough state:

To shape the splat I use a shoulder plane, rasp, spokeshave, sandpaper.  If one had a long belt sander this would work as well and faster - but the hand tool approach goes quite fast.  If the splat was wide or had a more complicated shape (i.e. a Chippendale style splat) then the hand tool approach would be the only option.

Here is the back where it meets the crest rail:

Before glue up I clean the ends of the crest rail with a sanding drum on my drill press.  I get very close but leave a smidgen which I can easily sand down flush with the rear posts after glue up.  The end flares out a bit - a thick 1/8" or so.  This gives it a nice look.

 

While I'm at it, I shape and glue on side cleats for the rabbet.  Later I'll glue on some strips at the bottom to complete the rabbet all around for the upholstery. 

If I build this again I will probably integrate the bottom rabbet into the rear rail rather than glue on cleats. However, for the sides I need to glue on cleats unless I go with lumber thicker than 8/4.