Green & Green Blacker House armchair - part III

To arms!

As I suspected, the arms for this chair is a non-trivial exercise!  This chair has the arms mortised to the front legs.  At the rear posts the arms are housed in a notch and secured with a screw.  The screw hole is covered with a large ebony plug on the inside of the rear post.  The fact that the front legs and rear posts are parallelograms and not square complicates matters, not to mention the various curves, slopes, tapers, etc.

There are probably a couple ways to construct and attach the arm.  A plywood template could be used to fine tune the precise location of the front mortise vis-a-vis the notch at the rear.  However, I decided to divide and conquer.  The front of the arm is stepped which lends itself to such an approach. 

Phase I:  I cut out a stub piece of wood from the arm blank.  Being from the same arm blank, the stub will have the same grain pattern as the rest of the arm above.  I then cut a mortise and a taper (as the arm slopes downwards towards the back).  I tapered the bottom of the stub so the entire stub will slope downwards in the same direction as the arm above and therefore have the same grain direction.

 

 

Phase II:  With the stub fitted, I can then fit the main body of the arm to the notch in the rear post.  Once that is fitted, I will simply surface glue the top of the arm to the stub.  I will leave a lot of extra wood (or slop) up front so I do not need to worry about an exact fit over the stub - no fussing. 

FIrst I milled the arm top to final thickness.  Then I spent a lot of time laying out my lines to determine how far I want to cut the bottom taper in the arm (making sure I leave enough slop up front).  I also layed out the lines for fitting the back of the arm into the notch in the rear post.  I checked and double checked my layout lines, being cautious of the fact that the front leg and rear post are parallelograms and that the angles on the rear post are slightly different due to the fact that I had hand planed parts of the rear post (just to make life interesting, I suspect).

I cut the bottom taper on the bandsaw then hand planed to my lines.

Next I cut a notch in the rear of the arm to fit the angle of the rear post. 

Next step is to clamp the arm pieces in place and then scribe with a knife the exact location of the notch in the rear post.

Once the notches are scribed, I then used a chisel and my dremel router to hog out the waste.  I went 1/8" deep - hope this is not too deep since during glue-up the arm needs to fit the front tenon and pop into the rear notch simultaneously.

A bit of promotion here:  For the dremel I'm using a plunge router base from Stewart MacDonald.  This base is very well made and what is great is that it has an inlet to attach a small air pump and hose.  This clears out the dust during routing - a wonderful feature.  I consider my dremel and this base and accessories mandatory in my shop.  I also bought a set of 5 downcut carbide spiral bits - from 1/32" to 1/8".  They work great.

I think I'll call this post done for now.  I'll finish the arm in another posting.