Green & Green Blacker House armchair - part VII

Splines and attaching the arms and glueing up the splats!

Here is the original.  Check out the beautiful ebony splines on the arms.

Before attaching the arms it makes sense to cut the splines in the arms.  Now, if I build this chair again I will definitely attempt to cut the splines on the router table before glueing up the chair. Unfortunately, I have already glued up part of the chair to make cutting the splines with a router table impossible.

I could try routing free hand.  On Darrell Peart's website I see that he cuts the top arm splines free hand for his rocker (not sure about the splines under the arm). I toyed with the idea of using a router free hand.  But I seem to have had trouble getting the router positioned correctly to handle the parallelogram shape of the arm - especially with part of the chair glued up already.  I did not have a warm and fuzzy feeling using the router free hand.  One thing about the parallelogram arms - a bearing will not ride flush to the bearing face but on edge with the consequence that the bearing will dig a nice bearing groove into the wood.  I wonder how folks handle this.  I tried on some scrap and got bearing marks on the wood - even through a couple layers of tape to protect the wood.

I finally decided to grab the marking gauge and chisel.  I will use the marking gauge to define an undersized groove and then chop a 1/4" deep mortise with a chisel.  Since it is undersized I will not worry about thrashing the side walls a bit.  This went surprisingly fast.  I aligned the chisel not 90 deg to the surface to be chopped but inline with the parallelogram side walls - so that the spline will slide in properly along the entire length.  Note that the front inside edge of the arm is a flat reference surface.

Oh yes, I also cut the spline groove along the underside of the rear post - much easier now before glueing up the splats.

Note that the final groove size for the front of the arm (top and below) is 5/16 and the groove size on the rear post under the splat is 1/4".  Consequently, for rough cutting the undersized grooves I cut 1/4" grooves up front and a 3/16" groove on the rear post.


Now that the grooves are roughly chopped, it is time to glue up the arms, drill and insert the screw to reinforce the rear arm to the rear post, and then plug up the screw hole with a 1/2" square ebony plug.

I had some small scraps of ebony so I defined the ebony plug by hand planing 2 reference surfaces (90 deg to each other) and then using the bandsaw and hand plane till it fit the mortise.  I shaped the top of the plug to give it a pillow effect - using sandpaper then eventually the buffing wheel (see Darrell Peart's book on how he does this)


Now that the arms are attached to the chair I can then define the final width of the grooves with the marking gauge.   No chopping here - just slicing.  Since I will be slicing very little wood I can also go pretty deep to help define the side walls about a 1/16" deep.  I then used a chisel to define the side walls all the way down, being very careful not to gouge the cleanly sliced top edge.


OH NO!!!!! Everything was going fine until the very last groove on the top of the right arm.  I got distracted than came back and did not tighten the marking gauge - the gauge wondered off course and, oh crap!  Well, after much cussing, regrouping, cussing some more, I had to re-define the groove with the marking gauge for the top of both arms - to fix the mistake, re-center the groove, and then to make both arms consistent.  Well, rather than a 5/16" groove on top I now have a 7/16" groove.  Did I say I am sorely pissed?  Needless to say, a 7/16" ebony spline may look heavy and lack balance with the other ebony splines and later the plugs.  Did I say I am sorely pissed?

Well, time to move on (did I say I am sorely pissed?). 

Nothing like a new machine to lift up the spirits.  During this time I bought a Jet 10-20 drum sander.  I bought this sander specifically for handling small pieces that can be awkward or dangerous in a planer or tablesaw.  I can sand a piece as short as 2 1/4" inch long - and sand off only a thousandth of an inch - a nice feature when dealing with ebony that costs an arm and a leg.  I'm using only 120 grit - rough enough to take off material without burning but not too rough to leave a nasty surface.  (I would not use this drum sander to sand lots of board feet.  I think one would have to go to a much more powerful machine for those tasks).  

Below I bandsawed the ebony spline for under the splat then used the drum sander to get a perfect fit.  (I will make a rolling cart for the new machine later).

For the arms, I cut out some paper templates to represent the inside curve of the spline mortise.  I cut a piece of ebony to rough thickness on the bandsaw and then used the drum sander to achieve final thickness.  Then I layed out the inside curve on the ebony and bandsawed that curve out.  I had to clean the side walls of the spline mortises here and there - being careful to not touch the cleanly sliced top.

I had to fix one side wall that got dinged up a bit - I'll glue the fix during final glue up.

Then I used a pencil to mark out where the spline meets the surface - and then bandsawed the waste about 1/8" over.  Here is what they look like.

I then glued up the arm splines underneath then prepared the top splines the same way as the bottom splines.  I had to cut new ebony since the top spline is now 7/16" wide (did I say I am sorely pissed?).

There was a little bit of fussing to make sure the 2 spline sections were nice and tight where they meet.  I used a shooting board and handplane to slice the lower spline length shorter till I got a nice tight fit.

Glue-up.  I took some sandpaper and sanded a bit of mahogany-glue slury to fill any minor gaps around the spline.

Now for final shaping.  I tried using a rasp but a couple times I came dangerously close to blowing out the ebony side wall.  I grabbed my dremel and slapped on a coarse sanding wheel - this worked very well and got me down to about 1/32 over.  I then used a combination of file, sandpaper, and spokeshave to get the final shape.

Are the top splines too heavy???  Because the spline is now so wide it appears rather flat.   Oh well - move on.

While I'm add it - now is a good time to glue up the splats.  Given that there are so many splats and those little doohickeys between the splats I glued the splats in 2 phases.  First, I glued the splats to the bottom rail - dry fitting the top crest rail only.  The next day I glued the top crest rail.

It's finally looking like a chair!